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Inverting & non

-

inverting

OP

-

Amplifiers

RFIC Laboratory

Academic Advisor : Prof. Nam-Young Kim

Kwangwoon Univ.

ITRC RFIC Center17thMar, 2009

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Contents

Objectives

Theory of Non-inverter OP Amplifier

Theory of inverter OP Amplifier

Applications of Operational Amplifiers

Simulation and Results

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Objectives

1. To Familiarize the Application of Op-amp as a Non-Inverting Amplifier

2. To Familiarize the Application of Op-amp as an

Inverting Amplifier

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Non-inverting Amplifier

Vi

V

V

d

2

+

- Vo

R

R

2

1

The voltage at both inputs must be equal.

No current flows into either of the op-amps inputs, so potential divider

R1 and R2 determine the voltage at the inverting input.

So voltage Vi applied to the non-inverting input causes the output

voltage to become positive until the fraction at the inverting input is equal.

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Non-inverter Op-Amplifier

Non-inverter OP Amplifier

Vi

V

V

d

2

+

- Vo

R

R

2

1

2 1

2

1

2

1

0 for

1

O

IO I

O

I

vv v A

A

vv v RR

v R

v R

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Non-inverting Amplifier

Vi

V

V

d

2

+

- Vo

R

R

2

1

In another way,

If, V0= AVd

Vd= ViV2

Then, V2= V0xR2/(R1+R2)

Considering that,

V2 = V0

So, = V2/V0= R2/(R1+R2)

Then, V0 = A Vd = A (Vi - V0)

Hence, the closed loop gain of the amplifier becomes,

ACL= VO/Vi = A /(1 + A)

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1

2

2

1

211

11

11

0

RR

vv

RR

vRivv

Rv

Rvvi

I

O

IO

II

+

Closed-loopOpen-loop

A -R2 /R1

Poor Good

Gain

Accuracy

Inverting type Amplifier

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Inverter Op-Amplifier

Inverting type OP Amplifier

Vi

+

-

Vo

R

R

2

1

V d

I = (VdV0)/R2= (VdAVd)/R2= (1-A)Vd/R2

Vi = IR1

And, V0 = - IR2

So, Closed loop gain of Inverting amplifier becomes,

ACL= V0/Vi= -IR2/IR1= - R2/R1

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Application of Op-amps

Analog Calculators

Voltage Comparator

Digital to analog Converter (DAC)

Analog to digital Converter (ADC)

Summers

Differentiators

Integrators

Precision Rectifiers

Voltage Clampers

Amplifiers with various gain Oscillators and

Waveform Generators etc..

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Application of Op-Amp: Weighted Summer

1 2

1 2

1 2

1 2

1 21 2

, , ...,

...

0

...

nn

n

n

O f f

f f f

O nn

vv vi i i

R R Ri i i i

v iR iR

R R R

v v v vR R R

+

-

-

+

Ov

1R

fR

2R

nR

1i

2i

ni

i

0 V

1v

2v

nv

i

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Modified Inverting Configuration for HigherRi

3

4

2

4

1

2

1 R

R

R

R

R

R

v

v

GI

O

For G= 100 andRi= 1 MW

R1= 1 MW,R2=R4= 1 MW,R3=10.2 kW

Compared toR1= 1 MW, andR2= 100 MWfor the conventional case

+

-

+

-+

-

-

+Iv

1v

1i

2i

3i

4i

Ov

1R

2R

3R

4R

0

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Non-Inverting Amplifier Simulation

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Non-Inverting Amplifier Simulation Result

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Inverting Amplifier Simulation

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Inverting Amplifier Simulation Result

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Thank You!

Any Questions Please.

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I have some questions.

Why is it named Operational Amplifier (Op-amp)?

What is the meaning of open-loop gain?

What do you mean by closed-loop gain?

Why Op-amp is also called versatile amplifier?