INTRODUCTION

(1) Linear Integrated Circuits (Linear ICs), and (2) Digital Integrated Circuits (Digital ICs). Linear ICs accept analog inputs and deliver analog

outputs. Examples of linear ICs are given below.• Operational Amplifiers (op-amp) 741• Timer IC 555• Phase Locked Loop IC 565• Voltage Regulator IC 723• Waveform Generator ICs (8038)

• Digital ICs accept input in two discrete voltage levels, viz., logic 0 (zero) or logic 1 (+ 5 V). The output is also discrete in two specific voltage levels only. Due to this, noise immunity is better in digital circuits, compared to analog circuits. The noise signal is analog in nature and it also gets processed along with input in analog ICs and (linear ICs), unlike in digital ICs. Examples of digital ICs are given below.

• Logic Gates 7400, 7404• Multiplexers• Microprocessor: 8085, 8086, 80486

General Classification of ICs

OPERATIONAL AMPLIFIERS

some of the special function op-amps are:• Video/Audio ICs• Instrumentation applications• Sonar send/receive modules• Communication ICs

SYMBOL

Package

• Op-amps are available in three commonly used packages—TO-5 (Metal can), Dual-in-Line Package (DIP), and ceramic flat package

• The package of the IC is denoted by a code as follows.

• D: Plastic Dual-in-Line Package• J: Ceramic• N, P: Plastic;• Dual-in-Line, for insertion into socket

IC Manufacturers and Letter Prefixes

Temperature Ranges

Nomenclature

OPERATIONAL AMPLIFIER PARAMETERS

Input Offset Voltage (Vio)

input offset voltage- It is the voltage that must be applied between the two input terminals of an op-amp to nullify output.

Practical value 100 μV (typical).

Input Offset Current (Iio)

The algebraic difference between the currents into the inverting and non-inverting terminals is referred to as input offset current Iio.

Iio = |IB1 − IB2|

For an ideal op-amp, Iio = 0. The typical value for a practical op-amp = 100 nA For precision op-amp 741C, the value typically is 6 nA.

Output Bias Current (IB)

This is the average of the currents that flow into the inverting and non-inverting input terminals of the op-amp

For an ideal op-amp IB = 0 AmpsFor a practical op-amp IB = 500 nAFor a precision op-amp, IB is typically 10 nA

Input Resistance (Ri)

This is the equivalent resistance of the IC measured at either the inverting or non-inverting input terminal, with the other terminal connected to the ground.

• Ideal value = ∞Ω, Practical value = 2 MΩ• For JFET op-amps, typical value of Rt is 1012Ω.

Input Capacitance (Ci)

• This is the equivalent capacitance, Ci, that can be measured at either the inverting or non-inverting terminal, with the other terminal connected to the ground.

• Ideal value of Ci = 0 pf, Practical value = 1.5 pf

Common Mode Rejection Ratio [CMRR (ρ)]

• This parameter indicates the capability of the op-amp to reject noise. The higher the value of CMRR, the better it is.

• CMRR is defined as the ratio of the differential voltage gain, Ad, to the common mode voltage gain, Acm. (cm = common mode)

• The op-amp has a differential voltage amplifier configuration. Ad is usually large. Acm is small. Hence, the value of CMRR is large. CMRR is expressed in decibels.

Power Supply Rejection Ratio (PSRR)

• The input offset voltage Vio of the op-amp changes if the bias power supply of the op-amp. changes. The change of Vio with + Vcc or −Vcc is called the power supply rejection ratio. The term is also called the Supply Voltage Rejection Ratio (SVRR) or Power Supply Sensitivity (PSS).

Gain BW Product (Av. BW)

This is the bandwidth of the op-amp when the voltage gain is 1 (unity).

• As the frequency increases, the gain decreases because as f increases, decreases. So ZL also decreases. Hence, V0 = IL · ZL also decreases. So the gain Av decreases. The gain BW product indicates the capability of the op-amp to amplify the input signals of larger frequency.

• The other terms used to describe Av. BW are closed loop

bandwidth, unity gain bandwidth.

Offset Voltage Adjustment

FREQUENCY ROLL OFF

• The decrease in voltage gain of the op-amp. with frequency is called frequency roll off. The rate of decrease of gain with frequency is expressed in db/octave or db/decade.

• 1.6.1. Octave• When the frequency changes from f1 to f2 such that f2 = 2f1, it is

referred to as octave number. That is, when frequency doubles, if the gain decreases by 20 db, it is referred as db/octave.

• 1.6.2. Decade• When the frequency changes from f1 to f2 such that f2 = 10f1, it is

referred to as decade.• If the gain decreases by 100 db when the frequency changes from 1

MHz to 10 MHz, then the fall in gain is referred to as 100 db/decade.

OPERATIONAL-AMPLIFIER GOING TO SATURATION

VIRTUAL GROUND

OP-AMP—A DIRECT COUPLED HIGH GAIN AMPLIFIER

deal characteristics of op-amp.• Infinite input impedance• Zero output impedance• Infinite voltage gain• Infinite bandwidth• Infinite CMRR• Zero drift• Perfect balance, that is, V0 = 0, V1 = V2

INVERTING AMPLIFIER