1

Chapter 8 The Operational Amplifier (Part I) ~ Using PSpice

The Ideal Op Amp Noninverting Ideal Op Amp Op Amp Giving Voltage Difference Output Frequency Response of the Op Amp Using a Subcricuit for the Op Amp Op Amp differentiator Circuit Op Amp Integrator Circuit Response to Unit Step Function Double Op Amp Circuit

2

The Ideal Op Amp High input resistance, zero output

resistance, and high voltage gain

3

The Ideal Inverting Op Amp

Negative feedback connection

PSpice version of the circuit

4

Input FileIdeal Operational AmplifierVS 1 0 1VE 3 0 0 2 200E3RI 2 0 1GR1 1 2 1KR2 3 2 10K.OP.OPT nopage.TF V(3) VS.END

5

Run the Analysis and Verify Run V(3)/VS=-9.999 Verify Vo/Vs=-R2/R1=-10K/1K=-10

6

Noninverting Ideal Op Amp

Noninverting ideal op amp

Noninverting ideal op amp model

7

Input FileIdeal Operational Amplifier, NoninvertingVS 1 0 1VE 3 0 1 2 200E3RI 1 2 1GR1 2 0 1kR2 3 2 9k.op.opt nopage.TF V(3) VS.END

8

Run and Verify V(3)/VS=10, Vo/Vs=1+R2/R1=1+9K/1K=10

9

Op Amp Giving Voltage Difference Output

10

Input FileOp Amp Giving Voltage Difference OutputVA 1 0 3VVB 4 0 10VE 5 0 3 2 200E3RI 2 3 1GR1 1 2 5kR2 5 2 10kR3 4 3 5kR4 3 0 10k.OP.OPT nopage .TF V(5) VB.END

11

Run and Verify Verify that Vo=R2(Vb-Va)/R1=10k(10v-3v)/5k=14v V(5)=14V

12

Frequency Response of the Op Amp

Model for the frequency response of an op amp

fc=10Hz

13

Input FileOp Amp Model with 3-dB frequency at 10 Hz for Open-Loop

GainVS 2 0 AC 1mVEG 3 0 2 1 1E5E 6 0 4 0 1RI1 3 4 1kRO 6 5 50 R1 0 1 10kRL 5 0 22kRIN 1 2 1MEGC 4 0 15.92uF.AC DEC 40 1 1MEG.PROBE.END

14

Run and View Output

15

Modify Input FileOp Amp Model with 3-dB frequency at 10 Hz for Open-Loop

GainVS 2 0 AC 1mVEG 3 0 2 1 1E5E 6 0 4 0 1RI1 3 4 1kRO 6 5 50 R1 0 1 10kR2 5 1 240k RL 5 0 22kRIN 1 2 1MEGC 4 0 15.92uF.AC DEC 40 1 1MEG.PROBE.END

16

Parameter Setting

17

Run and View Output

18

Using a Subcircuit for the Op Amp.subckt opamp m p voeg a 0 p m 1e5e c 0 b 0 1rin m p 1megril a b 1kc b 0 15.92uFrol c vo 50.ends

19

Op Amp Analysis Using SubcircuitOp Amp Analysis Using SubcircuitVS 2 0 AC 1mVR1 1 0 10kR2 3 1 240kX 1 2 3 opamp.AC DEC 40 100 1MEG.PROBE.subckt opamp m p voeg a 0 p m 1e5e c 0 b 0 1rin m p 1megril a b 1kc b 0 15.92uFrol c vo 50.ends.END

20

Op Amp Differentiator Circuit Vo=-dv/dt

21

Input FileDifferentiator CircuitV 1 0 PWL (0, 0 1s, 1V 2s, 0)C 1 2 2FR 2 3 0.5X 2 0 3 iop.subckt iop m p vori m p 1mege vo 0 p m 2e5.ends.TRAN 0.05s 2s.PROBE.END

22

Run and View OutputsV(1

)

Vo

23

Op Amp Integrator Circuit

24

Input FileIntegrator CircuitV 1 0 PWL (0 0 0.01ms, -1V 1s, -1V 1000.01ms, 0V 2s, 0V 2000.01ms, 1V 3s, 1V)R 1 2 0.5C 2 3 2 X 2 0 3 iop.subckt iop m p vori m p 1mege vo 0 p m 2e5.ends.TRAN 0.05s 3s.PROBE.END

25

Run and View Output

Vo

V(1)

26

Response to Unit Step Function

By definition, it remains at zero volts until t=0, and from that time forward it is 1V.

27

Response of first-order circuit to unit step function

28

Input FileResponse to Unit Step Functi

on Vs 1 0 PWL (0, 0 1us, 1v 5s, 1v)C 2 3 0.125R 2 3 2 R1 2 0 1 X 2 1 3 iop.subckt iop m p vori m p 1mege vo 0 p m 2e5.ends.TRAN 0.05s 3s.PROBE.END

Vo(t)=(3-2e-4t)u(t)

29

Run and View Outputs

30

Double Op Amp Circuit

31

Input FileDouble Op Amp Circuit for Gain-Bandwidth Analysi

sVS1 2 0 AC 1mVR1 1 0 10kR2 3 1 240kX1 1 2 3 opampVS2 5 0 AC 1mVR3 4 0 10kR4 6 4 15kX2 4 5 6 OPAMP.AC DEC 40 100 10MEG.PROBE.subckt opamp m p voeg a 0 p m 1e5e c 0 b 0 1rin m p 1megril a b 1kc b 0 15.92uFrol c vo 50.ends.END

32

Run and View Outputs

OP Amp 1

OP Amp 2

33

Chapter 8 The Operational Amplifier (Part II) ~ Using Capture

Noninverting Ideal Op Amp Op Amp for Voltage-Difference Output Frequency Response of the Op Amp Frequency Response of the uA741 The uA741 as a Level Detector

34

Noninverting Ideal Op Amp

3

0

1mA

-+

+-

E1

E R2

9k2

R1

1k

1mA

Gain = 200,000

Ri

1G

0

Vs1V

1

Ideal op amp in Capture

Ideal op amp

35

Run and View Output

36

Op Amp for Voltage-Difference Output

2R1

5k Ri1G5

R4

10k

0

Vb10V

R2

10k1

Gain = 200,000

Va3V 4

R3

5k 3

-+

+-

E2

E

37

Run and View Output

38

Frequency Response of the Op Amp

39

Op amp model for fc=10Hz

R1

10k

5R2

240k

0

Vs1mV0Vdc

2

4Gain = 100,000

Gain = 1

Ro

50

-+

+-

EG

E

3 6

Rin

1Meg

C15.92uF

-+

+-

E

E

Ri1

1k

1

40

Simulation Setting

41

Run and View Output

20*log10(V(5)/V(2))

42

DB(V(5)/V(2))

43

Frequency Response of the uA741

4

V+

15V

V-

15V

R1

10k

R2

240k

2

5

1

0

3

U1

uA741

3

2

74

6

1

5+

-

V+

V-

OUT

OS1

OS2

Vs1mV0Vdc

44

Run and View OutputFrequency response of the uA741

45

The uA741 as a Level Detector

R1

1k

V-9V

5

U1

uA741

3

2

74

6

1

5+

-

V+V-

OUT

OS1

OS2

4

V1

1

V+9V

Vref

3V

3

2

0

46

V1 (VPWL) Settings

(0v, 0s), (3v, 0.2s), (5v, 0.4s), (-5v, 0.6s), (-3v, 0.8v), (0v, 1s)

47

Simulation Settings

48

Run and View Output

V(5) Output

V(1) input

49

Question & Answer