56378023 final-report-e-e

DESIGN AND DEVELOPMENT OF OPERATIONAL AMPLIFIER TRAINER AND DESIGNER KIT

1. COMPANY PROFILE

The company Electronics & Electricals established in 1961, the organization made a modest

beginning by manufacturing different types of Electronic Test & Measuring Instruments

required for education, research and industry. This was supplemented by trading activities in

the same field. Initially the manufacturing activities started with manufacture of Electronic

Test & Measuring Instruments like Cathode Ray Oscilloscope, Power Supply unit, Oscillator,

LCR Bridge, Conductivity Bridge etc. However, during last nearly 46 years the product mix

has undergone many changes depending on the requirement of the. Presently, nearly 225

different types of ELECTRONIC TRAINING MODULES used in undergraduate science

and engineering streams are being manufactured by them.

Products- General Electronic Training Module

Characteristics

Amplifiers

Oscillators

Power Supply

General

Trainers

Digital

Ac Bridges

Network

Analysis

Communication

Instruments

Equipment For B.Sc. Class

B.Sc. I

B.Sc. II

B.Sc. III

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2 INTRODUCTION

2.1 Operational Amplifier IC 741:-

An operational amplifier, often referred to as an OP-AMP, is a very high gain, high

performance amplifier designed to amplify AC and DC signal voltages. Modern integrated

circuit technology and large scale production techniques have brought down the prices of such

amplifiers within reach of all users. The OP-AMP is now used as a basic gain element, like an

element transistor, in electronics circuit.

A symbol used to represent an operational amplifier in schematics is shown in fig. The

operational amplifier has two inputs and only one output. One input is called the inverting

input and denoted by a minus sign. A signal applied to this input appears as an amplified but

phase inverted signal at the output. The second input is called a non-inverting input and is

denoted by a plus sign . A signal applied to this input appears at the output as an amplified

signal which has the same phase as that of the input signal.

The availability of two input terminals simplifies feedback circuitry and makes the

operational amplifier a highly versatile device. If a feedback is applied from the output to the

inverting input, the result is negative feedback which gives amplifier with precisely controlled

gain characteristics. On the other hand, if the feedback is applied to the non-inverting input,

the result is positive feedback which gives oscillator and multivibrators. IC 741 has achieved

a very wide popularity. It is available in 8 pins dual-in-line package. Pin diagram of IC 741 is

shown in fig .

Operational amplifier type IC 741 has many features that have made it so popular. It has a

built in circuitry that provides full protection against output overloads or even shorts to

ground for any length of time. The IC 741 does not need any external component for phase

compensation or adjusting its frequency response. Its frequency response has a smooth roll-

off at the high end which keeps the circuit fully stable in all feedback.

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Fig. Pin diagram Fig: Ideal Op-amp

2.2 Ratings

Parameter conditions Min Typical Max UnitsInput offset voltage ± 5 1 5 mVInput offset current 20 200 nAInput bias current 80 500 nAInput resistance 0.3 2 M ΩInput capacitance 1.4 6 pFoffset Voltage Rl≥2kΩ,Vout= ±10V ±15 mVAdjustment Range output resistance 75 Ωsupply current 1.7 2.8 mASlew rate Rl ≥ 2kΩ 0.5 V/µs

2.3 Operational Amplifier IC LM358

LM 358- This device consist of two independent, high-gain frequency-compensated

operational amplifiers designed to operate from a single supply over a wide range of voltages.

Operation from split supplies also is possible if the difference between the two supplies is 3 V

to 32 V (3 V to 26 V for the LM2904), and VCC is at least 1.5 V more positive than the input

common-mode voltage. The low supply-current drain is independent of the magnitude of the

supply voltage.

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Applications include transducer amplifiers, dc amplification blocks, and all the conventional

operational amplifier circuits that now can be implemented more easily in single-supply-

voltage systems. For example, these devices can be operated directly from the standard 5V

supply used in digital systems and easily can provide the required interface electronics

without additional ±5V supplies.

Fig: LM 358

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CIRCUIT MAKINGTESTING WITH DIFF.SPECIFI-CATIONSMAKING OBSERVATION S COMPONENT PLACEMENTPCB DESIGNING

PACKAGING AGAIN TESTING


2.4 BLOCK DIAGRAM

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2.5 LITERATURE WORKOBJECTIVE:-To study OP-AMP in different following configurations

Op amp-Characteristics

Open Loop Gain Of Op-Amp

Input And Output Of Op-Amp

Input Offset Current Of Op-Amp

Slew Rate Of Op-Amp

Input Bias Current Of Op-Amp

The Common Mode Rejection Ratio

The Voltage Gain Of Op-Amp

Input And Output Impedance Of An Op-Amp

Op amp-Applications

Voltage Follower

The Inverting Amplifier

Non-Inverting Amplifier

The Adder

Scaling Amplifier

Average Circuit

Subtractor

Diffrentiator

Integrator

Astable Multivibrator-(Square Wave Generator)

Monostable Multivibrator

Clipper

Clamper

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Active Low-Pass Filter

Active High-Pass Filter

Band Pass Filter

Wien Bridge Amplifier

Schmitt Trigger

Schmitt’s Circuit (Solid State)

Log And Antilog Amplifier

Regulated Power Supply (Voltage Regulator )

Voltage Comparator

Digital -To-Analog Converter

Dead Band (Zone) Circuit

Phase Shift Oscillator

Pulse Generator Of Op-Amp

Peak Detector

Study Root Extractor

Voltage To Current Converter

Voltage To Frequency Converter

Frequency To Voltage Converter

Half Wave Precision Rectifier

Full Wave Precision Rectifier

Instrumentation Amplifier

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2.5.1 Open Loop Gain Of Op-Amp

Theory- This is the gain of the op-amp if a signal is fed differentially into the input of the

op-amp and no feedback loop is present. This gain is ideally infinite, but in a real op-amp

the maximum gain is finite (about 105). The gain also depends strongly on frequency. For

low frequency inputs it takes on its maximum value, but the gain decreases rapidly as the

input frequency goes up. For a 741 Ic, the gain decreases until it is only 1 at 1MHz.

Fig.-Open loop gain

2.5.2 Input And Output Of Op-Amp

Theory- The amplifiers output will be zero when the voltage difference between the

inverting and non-inverting inputs is zero. Ideal amplifiers produce 0V out for 0V input.

But, since the practical case is not perfect, a small DC voltage will appear at the output,

even though no differential voltage is applied. This DC voltage is called the input offset

voltage.

Fig.-Input and output of op amp

2.5.3 Input offset current of Op-amp

Theory- Idealy Input offset current should be Zero - Because the ideal op-amp has an

infinite input resistance, it draws no current (it looks like an open circuit). Each input draws

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a small amount of current. The difference between the amount of current drawn into the

positive and negative input terminals is called the input offset current.This can cause errors

in the output voltage. The difference between the currents into the two input terminals with

the output held at zero.

2.5.4 Slew Rate Of Op Amp

Theory-An ideal Op-amp has an infinite frequency response. This means that no matter

how fast the input changes, the output will be able to keep up. In a real Op-amp, this is not

the case. If the input signal changes too fast then the output will not be able to keep up. This

is defined as slewing and it results in distortion of the output waveform. Stated more

formally, or the maximum rate at which the output can change without distorting. This can

be measured by applying a high frequency square wave signal. The frequency of the

waveform should be increase until the waveform becomes a triangular wave. The slope of

the triangular waveform is the slew rate. (SR = ”V/”T)The unit of slew rate is V/µs. The

slew rate is same for both when feedback is considered or not considered:

Slew rate = maximum dvo/dt

fig.-Op-amp for Slew rate

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2.5.5 Input Bias Current Of Op-Amp

Theory- Input bias current Ib is the average of the currents that flow into the inverting

and Non inverting input terminals of the Op-amp. .

IB =( IB1+IB2)/ 2

Depending on the type of input transistor, the bias current can flow in or out of the input

terminals. The input current is modelled as current sources. Ib+ and Ib- in parallel with the

positive and negative input terminals Ib+ and Ib- are similar in magnitude; they are not

exactly the same. This difference called the input offset current, is described by-

Ib off = (Ib+) – (Ib-)

Fig.-Input bias current

2.5.6 The Common Mode Rejection Ratio

Theory- Common mode range - All input structures have limitations as to the range of

voltages over which they will operate properly. This range of voltages impressed upon

both inputs which will not cause the output to misbehave is called the common-mode range.

Most amplifiers possess common-mode ranges of +12V with supplies of +5V. The

common-mode rejection ratio (CMRR) of a differential amplifier (or other device)

measures the tendency of the device to reject input signals common to both input leads.

A high CMRR is important in applications where the signal of interest is represented by a

small voltage fluctuation superimposed on a (possibly large) voltage offset, or when

relevant information is contained in the voltage difference between two signals. (An

example is audio transmission over balanced lines) Ideally, a differential amplifier takes the

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voltages V + and V on its two inputs and produces an output voltage Vo = Ad(V + “ V” ),

where Ad is the differential gain. However, the output of a real differential amplifier is

better described as

Vo = Ad (V + “V “) + 1/2cm (V + “V “)

Where Acm is the common-mode gain, which is typically much smaller than the

differential gain. The CMRR is defined as the ratio of the powers of the differential gain

over the common-mode gain, measured in positive decibels (thus using the 20 log rule):

Fig-CMRR of ap amp

2.5.7 The Voltage Gain Of Op Amp

Theory- Theoretically it is Infinite - The main function of an operational amplifier is to

amplify the input signal and the more open loop gain it has the better, so for an ideal

amplifier the gain will be infinite.

Voltage gain is defined as the ratio of output voltage to an input signal voltage.

The voltage gain is a dimensionless quantity.

The Voltage Gain (A) of the amplifier can be found using the following formula

Voltage gain = Vout/Vin

Vout=Vin ((Rf/R1)+1)

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2.5.8 Input And Output Impedance Of An Op Amp

Theory- input impedance is Ideally Infinite - Input impedance is assumed to be infinite to

prevent any current flowing from the source supply into the amplifiers input circuitry. Input

impedance is the equivalent impedance that can be measured at either the inverting or non

inverting terminal with the other terminal connected to ground. For 741 IC this value is

relatively high Ideally Zero - The output impedance of the ideal operational amplifier is

assumed to be zero so that it can supply as much current as necessary to the load. Input

impedance is the equivalent impedance that can be measured at either the inverting or non

inverting terminal with the other terminal connected to ground. For 741 IC this value is 75

ohm.

2.5.9 Voltage Follower

Theory- If we made the feedback resistor, Rf = 0 then the circuit will have a fixed gain of

“1” and would be classed as a Voltage Follower and this type of Non-inverting amplifier

circuit is sometimes called a Voltage follower with gain. As the input signal is connected

directly to the non-inverting input of the amplifier the output signal is not inverted

resulting in the output voltage being equal to the input voltage, Vout = Vin. This then

makes the Voltage Follower circuit ideal as a Unity Gain.

One final thought, the output voltage gain of the voltage follower circuit with closed loop gain

is unity; the voltage gain of an idea l operational amplifier with open loop gain (no feedback)

is Infinite. Then by carefully selecting the feedback components we can control the amount of

gain produced by an Operational Amplifier anywhere from 1 to infinity.

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2.5.10 The Invering Amplifier-

Theory-An inverting amplifier uses negative feedback to invert and amplify a voltage. The

Rin, Rf resistor network allows some of the output signal to be returned to the input. Since

the output is 180° out of phase, this amount is effectively subtracted from the input, thereby

reducing the input into the operational amplifier. This reduces the overall gain of the

amplifier and is dubbed negative feedback.

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Fig: Op-amp as inverting amplifier

2.5.11 Non-inverting Amplifier

Theory- The second basic configuration of an operational amplifier circuit is that of a Non-

inverting Amplifier. In this configuration, the input voltage signal, (Vin) is applied directly to

the Non-inverting (+) input terminal which means that the output gain of the amplifier

becomes "Positive" in value in contrast to the "Inverting Amplifier" circuit we saw in the last

tutorial and whose output gain is negative in value. Feedback control of the non-inverting

amplifier is achieved by applying a small part of the output voltage signal back to the

inverting (-) input terminal via an Rf - R2 voltage divider network, again producing negative

feedback.

This produces a Non-inverting Amplifier circuit with very good stability, very high input

impedance, Rin approaching infinity (as no current flows into the positive input terminal) and

a low output impedance, Rout as shown below.

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Fig - Noninverting amplifier

2.5.12 The Adder

Theory-The adder circuit as shown in The output Vo of the adder is the sum of the two

input signals V1 & V2 given by following relation :

Vo = - Rf [( V1 / R1 ) + ( V2 / R2 )]

Where Rcomp is parallel combination of R1, R2 & Rf .

Fig-adder circuit

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Vo = - Rf [( V1 / R1 ) + ( V2 / R2 )]

2.5.13 Scaling Amplifier

Theory- A Scaling Amplifier can be made if the individual input resistors are “NOT”

equal. Then the equation would have to be modified

VOUT = V1 ( Rf/R1 ) - V2(Rf/R2) - V3(Rf/R3)

We can also rearrange the formula to make the feedback resistor Rf the subject and the output

voltage is found from.

VOUT =Rf [(V1/R1 ) + (V2/R2) - (V3/R3)]

Allowing the output voltage to be easily calculated if more input resistors are connected to

the amplifiers input. The input impedance of each individual channel is the value of their

respective input resistors, ie, R1,R2,R3… etc.

Fig. Scaling Circuit

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2.5.14 Average Circuit –

Theory- In average circuit the output voltage is equal to the average of all the input voltage.

The is accomplished by using all input resistors of equal value, R = R = R. In addition, the

gain by which each input is amplified must be equal to 1 over the number of inputs; that is ,

Rf/R = 1/n

where n is the number of inputs.

Thus, if there are there input we want Rf/R = 1/3. Consequently, from

Vo = - (Va+Vb+Vc)/3

Remember thet in the preceding application the input Va, Vb, and Vc could be either ac or dc.

These circuits are commonly used in analog computers and audio mixers, in which a number

of input is added up (mixed) to produce a desired output.

Fig.average circuit

2.5.15 SubtractorTheory- The subtractor circuit is as shown in fig. The output Vo of subtractor is the

difference of two input signals V1 & V2 given by following relation :

Vo = (V1 - V2)

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Fig: subtractor

2.5.16 Diffrentiator

Theory - As the name suggests , the circuit performs the mathematical operation of

differentiation, that is , the output waveform is the derivative of input waveform. The

circuit is as shown in fig.

The output voltage Vo is a constant [ -RfC1 ] times the derivative of the input voltage

Vi and the circuit is the differentiator . The minus sign indicates a 180° phase shift of

the output waveform Vo with respect to the input signal

So output voltage Vo is given below :

Vo = -Rf C1 [ dVi / dt ]

The magnitude of the gain of the differentiator as given below :

A = Vo / Vi = vRfC1 = 2pfRfC1

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Fig-Diffrentiator

2.5.17 Integrator

Theory- A low pass RC circuit can also work as an integrator as shown in fig.62.11 .

The output voltage Vo is a constant [ -1 / R1Cf ] times the integration of input

voltage Vi as given below :

Vo = [ -1 / R1Cf ] Vi dt

The magnitude of the gain of the integrator as given below :

A = Vo / Vi = 1 / vR1Cf = 1 / 2πfR1Cf

Fig- Integrator

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2.5.18 Astable Multivibrator-(Square Wave Generator)

Theory- A square wave generator using OP-AMP is shown in fig. Also called a free

running oscillator, the principal of generation of square wave output is to force an OP

AMP to operate in the saturation region. In fig.[a] a fraction ß = R2 / [R1 + R2] of the

output is fed back to the (+) input terminal . Thus the reference voltage Vref is ßVo and

may take values as + ßVsat or -ßVsat . The output is also fed back to the (-) input terminal

after integrating by means of a low pass RC combination. Whenever input at the (-) input

terminal just exceeds Vref , switching takes place resulting in a square wave output. In

astable multivibrator, both the states are quasi-stable. Consider an instant of time when the

output is at +Vsat . The capacitor now starts charging towards + Vsat through resistance R,

as shown in fig. 62.4[b] . The voltage at the (+) input terminal is held at ßVsat by R1 & R2

combination. This condition continues as the charge on C rises , until it has just exceeded +

ßVsat , the reference voltage. When the voltage at the (-) input terminal becomes just

greater than this reference voltage, the output is driven to - Vsat . At this instant ,the voltage

at the capacitor is + ßVsat . It begins to discharge through R , that is charges towards - Vsat

When the output voltage is switches to - Vsat , the capacitor charges more and more

negatively until its voltage just exceeds - ßVsat . The output switches back to + Vsat . The

cycle repeats itself as shown in fig. The frequency is determined by the time it takes the

capacitor to charge from - ßVsat to + ßVsat and vice-versa .The time period T is given

below :

T = 2RC ln[(1+ß)/(1-ß)

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2.5.19 Monostable Multivibrator

Theory- The circuit is as shown in fig. The monostable multivibrator has only one stable

output state. In this case a negative voltage is applied to the (-) input of the operational

amplifier. The stable output state is positive. This single shot can be triggered by

momentarily closing S. This applied a negative voltage to the positive input which caused

the output to go negative. As soon as the switch is opened however, C will begin to charge

through R. When the voltage at the positive input exceeds the voltage at the negative input,

the output will go back to its stable positive state. The delay between the instant of switch S

open and the return of the circuit to its stable state is determined by the values of C and R.

In practical applications switch S may be eliminated and the circuit triggered by negative

going pulses

.

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Fig- Monostable Multivibrator

2.5.20 Clipper :-

Theory- The circuit is as shown in fig a. A precision diode may also be used to clip-off a

certain portion of the input signal to obtain a desired output waveform. Fig (b) shows a

positive clipper. The clipping level is determined by reference voltage Vref and could be

obtained from the positive or negative supply voltages +V or -V. It can be seen that the

portion of the output voltage for Vo > Vref are clipped off. For input voltage Vi < Vref ,

diode D conducts. The OP AMP works as a voltage follower and output Vo follows input Vi

till Vi £ Vref . When Vi is greater than Vref , the output VoA of the OP-AMP is large enough

to drive D into cut-off . The OP-AMP operates in the open-loop and output voltage Vo =

Vref. However, if Vref is made negative, then the entire output waveform above Vref will

get clipped off.

Fig: clipper circuit

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2.5.21 Clamper

Theory- A clamper is a circuit that used to shift dc level of the input signal. It adds a desired

dc level to the ac input voltage. If the added dc level is positive, it is called a (+)ve clamper

and If the added dc level is negative, it is called a (-)ve clamper.

With Vref applied V0' is +ve & ‘D’ is on. V0 = +Vref

During –ve half cycle,V0' is +ve & ‘D’ conducts.

C’ charges to Vm.

During +ve half cycle,V0' is –ve & ‘D’ is –ve.

V0 =Vin+VC =Vm+Vm =2Vm

For –ve clamper, ‘D’ is reversed.

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Fig;Input And Output Waveform For Positive Clamper

Fig.:input and output waveform for negative clamper

2.5.22 Active low-pass filter :-

Theory- At low frequencies the capacitor appear open and the circuit acts like an

inverting amplifier with a voltage gain of R2 / R1.

As frequency increases, the capacitive reactance decreases, causing the voltage gain to

drop off. As the frequency approches infinity the capacitor appears shorted and the

voltage gain approches 0. In above fig. the output signal is maximum at low

frequencies.

A mathematical analysis leads to the formula for the cut-off freq :

fc = 1/2 πR2 C

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Fig. Active Low-Pass Filter.

Fig. Active Low-Pass Filter.

2.5.23 Active High-Pass Filter :-

Theory-At low frequency the capacitors appears open and the voltage gain

approaches 0. At high frequency the capacitor appears shorted and the circuit becomes a

voltage follower.

In summary a low-pass filter transmits low frequency but stops high ones, and in high-

pass filter the low frequencies are blocked and the high frequencies are transmitted.

Cut-off frequency :- Cut-off frequency is defined by a frequency at which voltage gain

is dropped to 70.7% of its maximum value.

Voltage gain :- Voltage gain is defined by the ratio of output voltage to input voltage

A = Vo / Vi

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2.5.24 Band Reject Filter-

Theory- A band reject filter ( also called a band stop or band elimination ) can be either (1) Narrow band reject or (2) Wide band reject filter. The narrow band reject filter is commonly called a notch filter and is useful for the rejection of a single frequency, such as 50 Hz power line frequency hum.

Frequency of perticular rejected frequency is given by :

f = 1 / 2 π R C

Cut-off frequency :-Cut-off frequency is defined by a frequency at which voltage gain is

dropped to 70.7% of its maximum value.

Voltage gain :-

Voltage gain is defined by the ratio of output voltage to input voltage :

A = Vo / Vi

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Fig. Band reject filter characterstics.

2.5.25 Wien Bridge Amplifier

Theory- Although it is comparatively easy to build an oscillator that approximates a sine-

wave making one that delivers a high purity sinusoid with a stable frequency and amplitude

is a task when this could be accomplished fairly in a low amplitude LC circuit, the

experiments attempted here are chosen to avoid the use of backward inductors and

concentrate instead on flexible RC circuits that are more practical for OP-AMP

applications.

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The Wien Bridge is the standard oscillator circuit for all low frequencies in the range of 5

Hz to 1 MHz. It is one of the promising type of circuit that is extensively used in

commercial audio generators.

The basic Wien’s network consists of a series connection of R C1 followed by a parallel

combination of R C1, the patch has a property of zero phase shift at a single frequency :

fo = 1 / 2 π RC ——————(1)

Since this combination is used as the positive feed-back elements, oscillation occurs at this

frequency of zero phase shift.

Amplitude stabilisation in the Wien bridge oscillator was traditionally achieved by

including a non-linear resistance (tungsten lamp) in the -ve feedback loop. However, this

function could be obtained by adding back to back connected diodes across a suitable value

of shunt adjustable resistance may be included to control distortion in output.

The typical OP-AMP version of Wien bridge oscillator circuit is shown in Fig.

patch chord between points X and G (output) and a patch chord between points Y and B .

increase by introducing more -ve feedback.

2.5.26 Schmitt Trigger

Theory- The circuit is as shown in fig. In a schmitt trigger circuit, the output is in one of

the two levels, namely, “Low” or “High”. When the input voltage is rising, the level of the

output changes, when the input passes through a specific voltage V-+

known as the “upper triggering level”. Similarly, when a falling input voltage passes

through a voltage V+- known as the “lower triggering level” the level of the output

changes. The voltage V-+ is always greater than V+-. The difference of these two

voltages is known as “hysteresis”. For IC 741 these voltages are 1.7 V and 0.9 V

respectively. So Schmitt trigger circuit converts a sinusoidal input into square wave output.

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2.5.27 Schmitt‘s Circuit (solid state) Theory- In digital circuits, fast waveforms are required so that the ckt. remains in the

active region for a very short time (of the order of nanoseconds) to eliminate the effects of

noise or undesired parasitic oscillations causing malfunction of the circuit. Also, if the rise

time of the input waveform is long, it requires a large coupling capacitor. Therefore,

circuits which can convert a slow changing waveform (long rise time) into a fast-changing

waveform (small rise time) are required. The circuit which performs this operation is

known as a Schmitt trigger. The Schmitt trigger circuit can be designed by using discrete

devices, OP AMP or gates.

In a Schmitt trigger circuit, the output is in one of the two levels, namely, LOW or HIGH.

When the input voltage is rising, the level of output changes, when the input passes

through a specific voltage Vt+ known as the upper triggering level. Similarly, when a

falling input voltage passes through a voltage Vt- known as the “lower triggering level “,

the level of the output changes. Vt+ is always greater than Vt-, the difference of these two

voltages is known as “hysteresis”. Fig. Shows the Schmitt trigger circuit using OP AMP.

Note that the operational amplifier like the differential amplifier has two inputs marked (-)

and (+). The minus terminal is inverting input & phase shift 180° at the output. The plus

input is the noninverting input. A signal applied to the plus terminal will appear in the same

phase at the output as at the input. Because of the complexity of the internal circuitary of an

OP-AMP, the OP-AMP symbol is used exclusively in circuit diagrams.

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2.5.28 Log and Antilog Amplifier-Theory- Multiplication and division are the most obvious uses of a lograthmic amplifier

if the output of two log amplifier are added and the sum used as the input to an antilog

amplifier, the final output will be proportional to the product of the two

input signals. The operations of the division, squaring or raising to a higher power can be

accomplished in a similar manner ( at least in principle). Log amplifier are commanly used

to compress an input signal that ranges over several decades in magnitude in a output signal

that varies over relatively narrow range of voltage or current. For example, we might wish

to use a 1V, full scale meter to monitor a voltage that range from 10 mV to 100mV. Using

nothing but a voltage divider to reduce the maximum 100V down to a usable 1V would

cause the low end of the range to be reduced to 100µV. A better solution would be a log

amplifier. Suppose that the constant B in eqn. (1) is set to be 0.060V and C to 0.400V. Then

an input of 10mV gives an output of 0.280V, while 100V gives 0.520V output. Clearly the

log amplifier. has disadvantages :

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It is difficult to dedect small changes in the input signal. All log amplifier. make use of the

current-voltage relation for a forward biased pn or np junction :

I = Io exp [qV /KT] -1 ..............(2)

In eqn. (2) Io is a constant, usually about 10-11 Amperes and +q/ kt is another constant

term that depends on temperature, q/kt equals 1/0.04V. The voltage across the junction

( forward biases ) is V, and the current that flows in 1. If V is considerably large than 0.04V

eqn.(2) reduces to

I = Io exp (V/Vo) where Vo = 0.04V. If we take the logarithmic (base 10) of our expression

for I, we find

Log10 I - log10 Io = 1/- 0.060V ..............(3)

The trick to making a logarithmic voltage amplifier is to notice that, if we can make the

current through the pn junction directly proportional to an input voltage, Vin, we can

rewrite eqn.(2) to obtain a result similar to eqn. (1). For the circuit in fig.1 we can say that

the input current Ii is equal to Vin/Ri, also the current through the diode D1 is equal to If

and If = Ii. You should notice that since the inverting terminal isat vertical ground the

voltage across the diode is simply equal to Vout. The diode will be forward biased Vout is

positive. In this case, we can rise eqn.(2) to write If = Io exp [qVout/KT] = Ii = Vin/R1 :Io

exp qVout/KT =Vin/R1 Taking the base 10 logarithmic of both sides yeilds an expression

similar to eqn.(1)

Vout = 0.060 log10 Vin - 0.060 log10 Io R1 ..............(4)

If we take I to 10-11 Amperes and Ri to be 100K Ohms the last term in eqn.(4) will be

0.360V. There are restrictions on the use of eqn.(4). The most serious condition is that Vin

must be negative so that the diode will be forward biased. Also, Vout should be larger than

25mV to allow us to ignore the -1 in eqn.(2). The current in the feedback loop may be quite

small. A typical value for If is 1uA thus an input bias current of greater than 0.1uA will

cause an appreciable error. Finally ifthe current through the, junction is appreciable, the

bulk resistance (usually less than 100 Ohms) can no longer be ignored. These difficulties

indicate that if accuracy and predictability are required it may be wise to by commercial log

amplofier. If an inexpensive OPAMP is used, the specified input bias current should be

chosen to be as low as posible. A glance at the table of OPAMP in appendix B suggests that

the best choise is an EFT input OPAMP such as the CA 3140 536 or 356. Another

SOI,DAVV,INDORE 32


posibility is the 308 OPAMP. The choice of choice kind of pn junction to use is rather

difficult. The best results are usually obtained with silicon junction of a transistor.

DISCUSSION (1) Two difficulties limits the response of the log amplifier.; input bias current and input

voltage offset. If the bias currents of the OPAMP are appreciable compared to the input

current, the output will be affected. A second difficulty, the input offset voltage becomes

important when the input voltage is small. An input voltage of 1mV is smaller then most

voltage offset encountered with inexpensive OPAMPs. To zero the output temporarily

replace the diode with a 1M Ohms or larger resistor. Set Vin to 0(ground it) and repeat your

offset control untill Vout is 0. Now replace the diode and repeat your measurement at-

1mv,-10mV etc.

(2) Antilog amplifier : To prform the mathematical operation of inverse log (which is

actualy exponential ). The diode need only be connected to the OP-AMP as shown in fig.3.

Measure, the input output characteristics of this circuit, you will notice the expected result.

Log10 Vout =A Vin +B ----- (5) is obtained only for a limited range of Vin (usually between

0.3 and 0.6V). Clearly, if your wish to use an antilog amplifier the input signal must be

conditioned to lie in the usable range of the amplifier.

SOI,DAVV,INDORE 33


Fig: log & antilog amplifier

2.5.29 Regulted Power supply (Voltage Regulator )Theory- In an unregulated power supply, the D.C. voltage decreases and the A.C. ripple

voltage increases as load current is increased. Both these disadvantages can be minimised by

adding a voltage regulator section to the unregulated supply. The regulating supply is known

as a voltage regulated power supply. Fig.1 shows a basic series regulator. The circuit achieves

regulation by comparing a simple of the output voltage with a reference voltage. The voltage

divider network consisting of R1 and R2 provides the sample signal and the reference voltage

is taken across a zener diode. The output sample is compared with Vz by the d.c. amplifier. It

produces a signal proportional to the difference between the two. The difference or error

voltage is amplified and it appears across R1 & R2. The d.c. amplifier may be a high gain

operational amplifier. The battery Vref is replaced by a zener diode and the bias resistor RD.

In input side there is a bridge type unregulated power supply. In fig. the effective bilateral

conduction of the semiconductor diode can be untilized in converting the a.c. line voltage into

a pulsating unidirectional voltage. Four diodes arranged in the form of a network. fig.

constitute a full-wave rectifier. During the -ve half of the input wave, diodes D1 and D3

conducts, while the direction of the charge flow through the load resistor is the same. The

rectified output may be thought as a combination of a d.c. component and a super-imposed

a.c. components called the ripple voltage

SOI,DAVV,INDORE 34


2.5.30 Voltage ComparatorTheory- The comparator is a circuit which compares an input signal with a reference

voltage Vr, when input voltage exceeds Vr , the comparator output takes on a value which is

very different from the magnitude of the output when the input voltage is smaller than Vr.

Practically OP AMP is simply a high gain amplifier designed to compare two inputs . In its

simplest form ,it accepts two input signal and delivers a “zero” or “one” output depending on

which input is larger.

Circuit description- Fig shows the circuit diagram of OP AMP based comparator. Here a

reference voltage Vr is fed at non-inverting terminal of OP AMP i.e. at pin no.3 and

variable input voltage Vi is fed to the inverting terminal i.e. at pin no.2 . Till the voltage at

inverting terminal remains below Vr , the OP-AMP remains in the positive saturation state

and we will obtain a voltage of +9 V to +12 V at output terminal 6. At Vi = Vr , the output

becomes zero and when Vi becomes greater than Vr , the output switches over to negative

saturation state.

SOI,DAVV,INDORE 35


Here in training modules, two zener diodes are provided to get two different reference

voltage. Also a variable 0-12 V power supply is provided to feed continuously variable

inverting input.

Fig. voltage comparator

2.5.31 Digital - to -Analog Converter

Theory- All phenomena, such as voltage, temperature, pressure, velocity etc. occur in

nature on an analog basis.This means that these variables can assume any value. These

variables are continuous and are known as analog variables. There are many advantages in

processing these signals in the digital fore. Therefore, it is frequently required to convert

date from the analog to digital or digital to analog form.

Thus the analog output voltage is directly proportional to the input binary number DCBA.

The commonly used performance parameters of a D/A converter are given below :

SOI,DAVV,INDORE 36


Fig- digital to analog converter

2.5.32 Dead Band (zone) circuit

Theory-- A dead band (zone) indicates an amount of signal below or a reference voltage.

This is reverse process as that of a comparator where o/p indicates signal level below or

above reference voltage. Dead band (zone) circuits are basically precision rectifiers with

biasing (reference).These circuit can be constructed to give negative, positive and both

negative -positive O/Ps.fig 1.1(a) shows dead band circuits with +Ve & -Ve O/ps.

Fig: dead band circuit with negative output

SOI,DAVV,INDORE 37


Fig: dead band circuit with negative output

Fig: dead zone circuit with bipolar out put

2.5.33 Phase Shift Oscillator

Theory--This circuit falls under RC Oscillators uses resistance-capacitance network

which determine the frequency of oscillation, phase shift oscillators are primarily used for

audio range and have desirable characteristics of low distortion, good frequency stability

and uniform output over a wide range.

This oscillator generally incorporates three sets of series and shunt phase shift elements,

offering network introduces a phase shift of 180°. When this phase shifting RC network is

included in the feedback loop of an amplifier operating with a gain more than 29 and

introducing an additional phase shift of 180°, oscillations can be set up at a frequency as

given below:

F = 1

2 πRC √6

SOI,DAVV,INDORE 38


The gain of the inverting OP-AMP should be at least 29, or Rf = 29 R1 to maintain

oscillations .

Fig.Phase Shift Oscillator

2.5.34 Pulse Generator Of Op-Amp

Theory-The circuit is as shown in below fig. C1 therefore charges through D1, R2 and R1

and discharges through R1, R3 and D2. The period for which the output is “HIGH” or

“LOW” can now be controlled independently by R2 and R3. Thus the pulse width and the

time interval between the pulses can be controlled to produce pulses of any duty cycle and

repetition rate by choosing C1 correctly and adjusting R2 and R3 properly.

SOI,DAVV,INDORE 39


Fig. op amp as pulse generator

2.5.35 Peak Detector

THEORY- To detect peak value of small signal a precision detector circuit is needed.

Precision circuit consists of precision rectifier & a capacitor across its O/P below fig. shows

peak detector. Diode & Op-amp offers rectification precisely with knee voltage in range of

few microvolt due to high gain of Op-amp (normal knee voltage of a diode is round

0.7V).Thus small signal can easily be rectified. A capacitor across the O/P charges to the peak

value & discharges according to the values .Hence the circuit shown in below fig. is useful

for peak detection of small signals.

Fig: peak detector

SOI,DAVV,INDORE 40


Fig: Peak Detector

2.5.36 Study Root Extractor

Theory- Root Extractor circuit employs a log amplifier, antilog amplifier and potential

divider. Block schematic of root extractor circuit is shown in fig,1.1

Output (Vout2) is nearly equal to the 1/Xth root of input voltage (vin). As shown in fig

1.1both log amplifier and antilog amplifier are connected together with potential divider

such that it will give 1/Xth root of the input voltage.Let us consider quantity "Vin"

whose 1/Xth root is to be found (Vin)

where X=2 or 3 or 4

By writing equation for Vout 2 as

Antilog [Vout3]=antilog [Vout1/X]

SOI,DAVV,INDORE 41


By substituting Vout 1=Log (Vin)

(Vin)1/X = antilog [1/xlog (vin)]

Hence this procedure suggests following experimentation and simulation.

Find out log of quantity to be 1/Xth rooted.such that log(Vin)

Find out its 1/X value using potentiometer. such that1/x log (vin)

Then find out antilog of value calculated.This antilog gives the 1/Xth root output of the

quantity ti be 1/Xth rooted, such that antilog [1/Xlog(vin)]

2.5.37 Voltage to Current Converter

Theory-In instrumentation circuitry, DC signals are often used as analog representations

of physical measurements such as temperature, pressure, flow, weight, and motion. Most

commonly, DC current signals are used in preference to DC voltage signals, because

current signals are exactly equal in magnitude throughout the series circuit loop carrying

current from the source (measuring device) to the load (indicator, recorder, or controller),

whereas voltage signals in a parallel circuit may vary from one end to the other due to

resistive wire losses. Furthermore, current-sensing instruments typically have low

impedances (while voltage-sensing instruments have high impedances), which gives

current-sensing instruments greater electrical noise circuit may vary from one end to the

other due to resistive wire losses. Furthermore, current-sensing instruments typically have

low impedances (while voltage-sensing instruments have high impedances), which gives

current-sensing instruments impedances), which gives current-sensing instruments greater

electrical noise immunity.

By introducing electrical reactance into the feedback loops of op-amp amplifier circuits, we

can cause the output to respond to changes in the input voltage over time. Drawing their

names from their respective calculus functions, the integrator produces a voltage output

proportional to the product (multiplication) of the input voltage and time; and the

differentiator (not to be confused with differential) produces a voltage output proportional

to the input voltage’s rate of change

integrator produces a voltage output proportional to the product (multiplication) of the input

voltage and time; and the differentiator produces a voltage output proportional to the input

SOI,DAVV,INDORE 42


voltage’s rate of change. Capacitance can be defined as the measure of a capacitor’s

opposition to changes in voltage. The greater the capacitance, the more the opposition.

Capacitors oppose voltage change by creating current in the circuit: that is, they either

charge or that is, they either charge or discharge in response to a change in applied voltage.

So, the more capacitance a capacitor has, the greater its charge or capacitor has, the greater

its charge or discharge current will be for any given rate of voltage change across it. The

equation for this is quite simple:

The dv/dt fraction is a calculus expression representing the rate of voltage change over

time. If the DC supply in the above circuit were steadily increased from a voltage of 15

volts to a voltage of 16 volts over a time span of 1 hour, the current

Fig. Voltage to current Converter

2.5.38 Voltage To Frequency Converter

SOI,DAVV,INDORE 43


Theory- Circuit is constructed around Op-amp IC LM 358 separately. Identify the circuit

on panel. Switch on the power supply .apply I/P signal as shown in the table below.&

Observe corresponding O/P frequency on C.R.O measure the O/P frequency for every I/P

voltage.

Aim of both F to V & V to F converter excepts are to show the linearity between the

voltage & frequency & vice versa. As both the circuits are independent, corresponding

frequency & voltage readings of both will not be correctly matching with each other.

Fig : voltage to frequency converter

2.5.39 Frequency to Voltage Converter

Theory- Circuit is constructed around Op-amp IC LM 358 separately. Identify the circuit on

panel. Switch on the power supply. Apply I/P signal & Observe corresponding O/P voltage on

voltmeter. Aim of both F to V &V to F converter expts are to show the linearity between the

SOI,DAVV,INDORE 44


voltage & frequency & vice versa. As both the circuits are independent, corresponding

frequency & voltage readings of both will not be correctly matching with each other.

Fig. frequency to voltage converter

2.5.40 Half Wave Precision Rectifier

Theory- One of the non-linear behaviours that is sometimes required in analog circuits is

rectification. Rectification is a process of separating the positive and negative portions of a

waveform from each other and selecting from them what part of the signal to retain.

In the case of half-wave rectification, we However only positive-going portions of the

output can choose to keep one polarity while discarding other waveform, which correspond

actually reach the output The direct feedback diode shunts any negative-going output back

to the “-” input directly, preventing it from being reproduced. The slight voltage drop

across the diode itself is blocked from the output by the second diode he load and, because

of the feedback, the output voltage is equal to the input. it from being reproduced. The

slight voltage drop across the diode itself is blocked from the output by the second diode.

The second diode allows positive-going output voltage to reach the output. Furthermore,

since the output voltage is taken from beyond the output diode itself, the op amp will

necessarily compensate for any non-linear characteristics of the diode itself. As a result, the

SOI,DAVV,INDORE 45


output voltage is a true and accurate (but inverted) reproduction of the negative portions to

the negative-going portions of the input signal.

Study the circuit diagram as shown below. Identify the required component on panel.

Make assembly of test set up as shown in circuit diagram. Connect plus minus 12V to

panel. Switch on power supply. Apply a signal of 1KHz, 0.5V(sine wave) to the input of

half wave rectifier. Observe input and output waveforms on CRO simultaneously. Measure

the amplitudes of input and output waveforms and record it. Now use other diode at O/P of

Op-amp & test the circuit by connecting a capacitor C across O/P of half wave rectifier you

will get DC equivalent to peak voltage at O/P. This effect will be pronounced at higher

frequency (10KHz).

Fig: Half Wave Precision Rectifier

2.5.41 Full Wave Precision Rectifier

Theory- The half-wave rectifier kept only those parts of the original input signal that were

positive (or negative). Is there a way to keep both halves of the input signal, and yet render

them both with the same output polarity? This is the behavior of a full-wave rectifier.

SOI,DAVV,INDORE 46


The full-wave rectifier depends on the fact that both the half-wave rectifier and the

summing amplifier are precision circuits. It operates by rectified signal and then adding that

signal at double amplitude to the original signal in the summing amplifier.

The result is a reversal of the selected polarity of the input signal.

Fig: full wave precision ractifier

2.5.42 Instrumentation Amplifier:-

Theory- Many industrial application require amplification of low level or weak signals

measured from remote place. Mostly such signals are from various transducers or sensors

used in industry for process control. Transducers such as thermocouple, strain gauges etc.

give low level electrical output & may be from distance place. Thus these low level signals

are required to be amplified precisely with low noice, low thermal drift/time drift to

generate output capable to drive indicators or display or other control circuitry.

An instrumentation Amplifier is basically a difference amplifier, having two inputs &

output is proportional to the difference between these two inputs.

Ideal instrumentation amplifier should exhibits the following properties.

1. Very high & Stable gain.

2. Infinite input impedance (common mode & differential mode) to avoid loading on input

source.

3. Zero output impedance.

SOI,DAVV,INDORE 47


4. Infinite common mode rejection ratio (CMRR) such that amplifiers should be very

sensitive to difference signal only & to reject or ignore common mode signals.

5. High gain stability.

6.Extremely high linearity between O/P & I/P.

7. No offset erros.

8.Zero drifts(Time and thermal)

three Op-Amps used as Instrumentation Amplifier : Identify instrumentation amplifier(In-

Amp)& its inputs and output terminals on the panel Circuit diagram of Instrumentaion

amplifier is given below, which is constructed using Quad Op-Amp IC LM324. Refer the

following procedures for better observation;

a) First set the output of In-Amp to zero by applying zero inputs refer the above offset

adjustment method.

b) Set the gain of In-Amp to minimum by rotating the Gain pot of 100K to fully clock-

wise i.e. at 0K range.

c) Use 10K POT for different resistance values of Vil-input side .First set this POT to zero

value (i.e.at fully Clock-wise) and then slightly rotate to Anti-Clock -wise for getting

different values.

Fig:.Instrumentation amplifier

SOI,DAVV,INDORE 48


3. Printed Circuit Board Designing

Printed Circuit Board - A printed circuit board, or PCB, is used to mechanically support

and electrically connect electronic components using conductive pathways, tracks or signal

traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred

to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic

components is a printed circuit assembly (PCA), also known as a printed circuit board

assembly (PCBA).

PCBs are inexpensive, and can be highly reliable. They require much more layout effort and

higher initial cost than either wire wrap or point-to-point construction, but are much cheaper

and faster for high-volume production. Much of the electronics industry's PCB design,

assembly, and quality control needs are set by standards that are published by the IPC

organization.

The inventor of the printed circuit was the Austrian engineer Paul Eisler who, while working

in England, made one circa 1936 as part of a radio set.

Originally, every electronic component had wire leads, and the PCB had holes drilled for each

wire of each component. The components' leads were then passed through the holes and

soldered to the PCB trace. This method of assembly is called through-hole construction. In

1949, Moe Abramson and Stanislaus F. Danko of the United States Army Signal Corps

developed the Auto-Sembly process in which component leads were inserted into a copper

foil interconnection pattern and dip soldered. With the development of board lamination and

etching techniques, this concept evolved into the standard printed circuit board fabrication

process in use today. Soldering could be done automatically by passing the board over a

ripple, or wave, of molten solder in a wave-soldering machine. However, the wires and holes

are wasteful since drilling holes is expensive and the protruding wires are merely cut off. In

recent years, the use of surface mount parts has gained popularity as the demand for smaller

electronics packaging and greater functionality has grown.

SOI,DAVV,INDORE 49

http://en.wikipedia.org/wiki/Surface-mount_technology

http://en.wikipedia.org/wiki/Wave_soldering

http://en.wikipedia.org/wiki/Dip_soldering

http://en.wikipedia.org/wiki/United_States_Army_Signal_Corps

http://en.wikipedia.org/wiki/Through-hole_technology

http://en.wikipedia.org/wiki/Solder

http://en.wikipedia.org/wiki/Radio

http://en.wikipedia.org/wiki/Paul_Eisler

http://en.wikipedia.org/wiki/Austria

http://en.wikipedia.org/wiki/IPC_(electronics)

http://en.wikipedia.org/wiki/Point-to-point_construction

http://en.wikipedia.org/wiki/Wire_wrap

http://en.wikipedia.org/wiki/Laminated

http://en.wikipedia.org/wiki/Industrial_etching

http://en.wikipedia.org/wiki/Conductor_(material)

http://en.wikipedia.org/wiki/Electronic_component


3.1 Block Diagram:

Printed Circuit Board Circuit Designing

SOI,DAVV,INDORE 50

Making Schematic layout

Circuit Designing Making Top layer Electric layer

Solder MaskSilk LayerGerber File Generation


3.2 Softwares Used In Pcb Circit Designing

1 ORCAD

2 CADSTAR

3 CorelDraw

4 CAM

3.2.1 ORCAD - Orcad is a proprietary software tool suite used primarily for electronic

design automation. The software is used mainly to create electronic prints for

manufacturing of printed circuit boards, .

This software we uses for making schematic diagram

As shown below in the orcads layout there are three power supply are presenting which are

± 5 volts, ± 10 volts, ± 15volts. We are using this power supply for op-amps applications

1. Mainly schematic diagram we make in this software for doing this we take new

project and than makes a library by select one component and than add files.

2. After this we take components from the library and and make the circuit as we

want.

We connect all the components with the help of nets and by this type we make schematic

diagram.

SOI,DAVV,INDORE 51

http://en.wikipedia.org/wiki/Printed_circuit_boards

http://en.wikipedia.org/wiki/Electronic_design_automation


http://en.wikipedia.org/wiki/Software


3.2.2 Cadstar- Cadstar is a Windows based EDA software for designing and creating

schematic diagrams and Printed Circuit Boards. The software is developed at Zuken's

Technology Centre, ZTC in Bristol, United Kingdom.

It is used to draw schematic diagrams of electronic circuits, place and track printed circuit

boards (PCB's) and provide the manufacturing information required of modern electronic

designs. Cadstar SI Verify is a new Cadstar solution that offers a complete post-layout

signal integrity simulation toolset, seamlessly integrated into Cadstar. It uses an accurate

transmission line simulation approach to analyze reflection and crosstalk effects, and to

calculate the relevant timing information and delays. It can be used interactively by the user

for selected nets as well as in batch-mode for an entire PCB sign-off simulation.

The required electrical parameters of transmission lines (phase velocity, inductance and

capacitance matrices, and characteristic impedances) are determined by a 2D field solver

using boundary element methods. The time domain signal integrity simulation offers a fast

calculation of reflection and crosstalk effects on printed circuit boards, considering also the

non-linear characteristics of terminations

3.2.2.1Block Diagram

The 'core' suite of CADSTAR programs consists of

the Design Editor (which includes the SCM Design and PCB Design applications)

the Library Editor;

P.R.Editor XR (and its 'high speed' version, P.R.Editor XR HS)

SOI,DAVV,INDORE 52

http://en.wikipedia.org/wiki/United_Kingdom

http://en.wikipedia.org/wiki/Bristol

http://en.wikipedia.org/wiki/Zuken

http://en.wikipedia.org/wiki/Printed_Circuit_Board

http://en.wikipedia.org/wiki/Schematic

http://en.wikipedia.org/wiki/Software


http://en.wikipedia.org/wiki/Microsoft_Windows


the Simulation Library Manager.

There are other CADSTAR programs that are cost options - SI Verify and CADSTAR 3D.

Each of these programs has its own icon which can be selected from the Start menu.

The relationship between the 'core' application is shown below:

SOI,DAVV,INDORE 53


3.2.2.2 PCB Design Procedures

Usually an electronics or electrical engineer designs the circuit, and a layout specialist designs

the PCB. PCB design is a specialized skill. There are numerous techniques and standards used

to design a PCB that is easy to manufacture and yet small and inexpensive.

Most PCBs have between one and twenty conductive layers laminated (glued) together in a

sandwich with insulating plastic. PCBs with more than two layers help construct complex or

dense circuits. They are not always used because they are more expensive, and the inner

layers are more difficult to inspect and repair.

In more complex PCBs, two or more of the layers are dedicated to providing ground and

power. These ground planes and power planes distribute power well. They also prevent radio

waves from antennas unintentionally formed by tracks. These planes are rectangular sheets of

foil that occupy entire layers (except for small holes to avoid unwanted connection to vias and

through-hole components). They distribute electrical power and heat better than narrow

traces. Sometimes solid metal PCBs with thin layers of insulation are used. The power

electronic substrate carries away waste heat when air cooling is impossible.

Four-layer PCBs with a ground and power plane are often used in high-quality, but cost-

conscious audio, avionics and medical electronics. Most consumer products have one or two

layers.

SOI,DAVV,INDORE 54

http://en.wikipedia.org/wiki/Power_electronic_substrate

http://en.wikipedia.org/wiki/Power_electronic_substrate

http://en.wikipedia.org/wiki/Power_plane

http://en.wikipedia.org/wiki/Ground_plane

http://en.wikipedia.org/wiki/Printed_circuit_board


The width and spacing of conductors (or "traces") on a PCB is very important. If the traces

are too close, solder can short adjacent traces, and the PCB will be difficult to construct or

repair. If too far apart, the PCB may be too large and expensive. When a PCB carries high

frequencies, traces may need to be exact widths and lengths to control the characteristic

impedance of the trace.

Some designs cut the ground plane or the entire PCB in strategic locations to control the

return paths of currents. The usual desire is to keep high voltages or frequencies away from

sensitive portions of a circuit. The actual properties of the design are critical, because in some

cases, cutting the ground plane makes the PCB into an antenna that radiates radio noise into

nearby equipment.

Removing large areas of copper wastes etchant and increases pollution. Also, a PCB etches

more consistently and tends to resist warping if all regions have the same average ratio of

copper to bare board. Therefore, designers may widen connectors, leave unconnected copper

in place, or cover large areas of what would otherwise be bare board with arrays of small,

electrically isolated copper diamonds or squares.

Most PCBs have alignment marks (called fiducials) and tooling holes to align layers. These

permit the PCB to be mounted in equipment that automatically places and solders

components. Some designs also have quality control patterns to measure soldering and

etching processes. In some cases, the test patterns are on break-off tabs that can be removed

before the PCB is installed.

Layers may be connected together through drilled holes called vias. Either the holes are

electroplated or small rivets are inserted. High-density PCBs may have blind vias, which are

visible only on one surface, or buried vias, which are visible on neither, but these are

expensive to build and difficult or impossible to inspect after manufacture. Good designers

minimize the number of vias to reduce the cost of drilling. On older, two-layer PCBs, it was

common to solder a wire through the hole.

A solder mask is a plastic layer that resists wetting by solder (the solder is said to "bead up"),

and keeps islands of solder from running together. It also protects the outside conductors

layers from abrasion and corrosion. Without the solder mask, the fiberglass-reinforced epoxy

SOI,DAVV,INDORE 55

http://en.wikipedia.org/wiki/Epoxy

http://en.wikipedia.org/w/index.php?title=Buried_vias&action=edit

http://en.wikipedia.org/w/index.php?title=Blind_vias&action=edit

http://en.wikipedia.org/wiki/Fiducial

http://en.wikipedia.org/wiki/Characteristic_impedance

http://en.wikipedia.org/wiki/Characteristic_impedance


appears a translucent off-white. Solder masks are usually green, but they may be found in

other colors.

A silkscreen legend on the top or bottom surface of the board provides readable information

about component part numbers and placement. This aids in manufacturing and repair. To aid

manual construction and repair, diodes, capacitors and integrated circuits are sometimes

oriented in the same direction.

New technology allows for the component designators to be printed directly onto the board

surface, saving time and money by doing away with silkscreens. This is sometimes done by a

special inkjet printer. A similar process has experimentally produced solder masks.

Radio transmitters and radio receivers are difficult to design. PCB designers working on them

must minimize parasitic effects due to layout of components, or take them into account with a

general model and use simulation software such as SPICE.

3.2.2.3 CORAL DRAW- CorelDRAW is a vector graphics editor. We uses this

softwares for text editing for clear illustrations. Its features includes

Dynamic guides, Smart Drawing tools, Export to MS Office or Word option, Virtual

Segment Delete tool, Unicode text support.

3.2.3 CAM- This software we uses for making gerber file

3.2.3.1 Gerber file- A Gerber File is a file format used by printed circuit board (PCB)

manufacturing machines to lay out electrical connections such as traces, vias, and pads (the

component "footprints" on the PCB). A Gerber file can also contain information for drilling

and milling the circuit board.

SOI,DAVV,INDORE 56

http://en.wikipedia.org/wiki/Footprint_(electronics)

http://en.wikipedia.org/wiki/Via_(electronics)

http://en.wikipedia.org/wiki/Signal_trace

http://en.wikipedia.org/wiki/Printed_circuit_board

http://en.wikipedia.org/wiki/Vector_graphics_editor

http://en.wikipedia.org/wiki/SPICE

http://en.wikipedia.org/wiki/Inkjet_printer

http://en.wikipedia.org/wiki/Screen-printing


It is a standard electronics industry file format used to communicate design information to

manufacturing for many types of printed circuit boards. In many ways, Gerber is the

electronics world's equivalent of PDF. This odd little format, a hybrid machine control

language and image, is a core component of the electronics manufacturing supply chain.

These files are generated by PCB CAD software, and are sent to manufacturers where they

are loaded into a CAM system to prepare data for each step of the PCB production process.

Fig-gerber file

Fig.:gerber file

SOI,DAVV,INDORE 57

http://en.wikipedia.org/wiki/Printed_circuit_board#Manufacturing

http://en.wikipedia.org/wiki/Computer-aided_manufacturing


3.2.3.2 Contents of a Gerber File

The content of a Gerber file is ASCII text (i.e. English letters, digits and a few special

characters) and looks like a human could almost read and understand. Here's an example:

G75*

G70*

%OFA0B0*%

%FSLAX24Y24*%

%IPPOS*%

%LPD*%

%AMOC8*5,1,8,0,0,1.08239X$1,22.5*%

%ADD10C,0.0080*%

D10*

X000281Y000835D02*

X002472Y006196D01*

M02*

When the format was first created, these commands called out instructions for a special

kind of machine called a photoplotter which used them to create a picture on photographic

film by precisely controlling a light source. Today, however, photoplotters aren't always a

part of the process and Gerbers are treated more like image files. So if we think why

doesn't the industry just use image files like postcript? It's a bit of a catch 22:

The machines use Gerbers because CAD/EDA/CAM software creates Gerbers and, the

software creates Gerbers because the machines use Gerbers.

This type we finally crecated gerber file and after this our PCB MANUFACTURED.

Developing of the PCB circuit designing is going on ………………………..

SOI,DAVV,INDORE 58

http://en.wikipedia.org/wiki/Photoplotter


References:1. D.Johnson and J.Hilburn, Rapid Practical Designs of Active Filters, John Wiley &

Sons, 1975.

2. H.Berlin, Design of Active Filters with Experiments, Howard W.Sams & Co., 1979.

3. Black, H. S., Stabilized Feedback Amplifiers, BSTJ, Vol. 13, January 1934

4. Op-amps and linear Integrated circuits by Ramakant Gayakwad edition 2nd

5. Design reference of “op amp for every one” by Texas Instruments August 2002.

Research Paper help

https://www.homeworkping.com/

SOI,DAVV,INDORE 59

https://www.homeworkping.com/

http://www.homeworkping.com/

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