CHAPTER 8

Operational AmplifiersOperational Amplifiers (OP- (OP-AMP)AMP)

Introduction to ElectronicsIntroduction to Electronics

Ref: Electronic Devices and Circuit Theory Ref: Electronic Devices and Circuit Theory BoylestadBoylestad

OP-AMP Common Op-Amp Applications

YTU-Dep. Electrical Eng. / Introduction to Electronics

1. Constant-gain amplifier

2. Voltage summing

3. Voltage buffer

4. Controlled sources

5. Instrumentation circuits

6. Active filters

OP-AMP Constant Gain Amplifier

YTU-Dep. Electrical Eng. / Introduction to Electronics

1R

RA fV

1

1R

RA fV

Inverting Amplifier

Non-inverting Amplifier

OP-AMP Voltage Summing

YTU-Dep. Electrical Eng. / Introduction to Electronics

3

32

21

1

VR

RV

R

RV

R

RV fffo

OP-AMP Voltage Buffer (Follower)

YTU-Dep. Electrical Eng. / Introduction to Electronics

1i

OV V

VA

iO VV

OP-AMP Current-Controlled Current Source

YTU-Dep. Electrical Eng. / Introduction to Electronics

in

in

f

out

in

f

out

inin

fout

R

V

R

V

RR

V

R

V

VR

RV

21 //

kIR

RII

R

RR

R

VI

RR

RRVI

RR

VI

o

ino

ino

ino

2

1

2

21

1

21

21

21

1

//

OP-AMP Low-Pass Filter, First-Order

YTU-Dep. Electrical Eng. / Introduction to Electronics

112

1

CπRfOH

1

1R

RA fv

The upper cutoff frequency and voltage gain are given by:

OP-AMP Low-Pass Filter, Second-Order

YTU-Dep. Electrical Eng. / Introduction to Electronics

The roll-off can be made steeper by adding more RC networks.

OP-AMP High-Pass Filter

YTU-Dep. Electrical Eng. / Introduction to Electronics

The cutoff frequency is determined by: 112

1

CπRfOL

OP-AMP Band-Pass Filter

YTU-Dep. Electrical Eng. / Introduction to Electronics

There are two cutoff frequencies: upper and lower. They can be calculated using the same low-pass cutoff and high-pass cutoff frequency formulas in the appropriate sections.

YTU-Dep. Electrical Eng. / Introduction to Electronics

OP-AMP Question-1

R1: 2.2 kΩ

Rf: 220 kΩ

Vs: 100 Sinwt (mV)

Vcc: ±12V

YTU-Dep. Electrical Eng. / Introduction to Electronics

OP-AMP Question-1

YTU-Dep. Electrical Eng. / Introduction to Electronics

OP-AMP Question-2

R1: 2.2 kΩ

Rf: 220 kΩ

Vs: 100 Sinwt (mV)

Vcc: ±9V

YTU-Dep. Electrical Eng. / Introduction to Electronics

OP-AMP Question-2

YTU-Dep. Electrical Eng. / Introduction to Electronics

OP-AMP Question-3

R1: 33 kΩR2: 22 kΩR3: 12 kΩ

Rf: 330 kΩ

V1: +0.2 (V)V2: -0.5 (V)V3: +0.8 (V)

Vcc: ±15V

YTU-Dep. Electrical Eng. / Introduction to Electronics

OP-AMP Question-3