Download presentation

Presentation is loading. Please wait.

1
ENTC 3320 Op Amp Review

2
**Operational amplifiers (op-amps)**

Circuit symbol of an op-amp Widely used Often requires 2 power supplies + V Responds to difference between two signals

3
**Ideal op-amp Characteristics of an ideal op-amp Rin = infinity**

Rout = 0 Avo = infinity (Avo is the open-loop gain, sometimes A or Av of the op-amp) Bandwidth = infinity (amplifies all frequencies equally)

4
**Model of an ideal op-amp**

V+ V Vout = A(V+ -V) + - I I+ Usually used with feedback Open-loop configuration not used much

5
**Summary of op-amp behavior**

Vout = A(V+ - V) Vout/A = V+ - V Let A infinity then, V+ - V

6
**Summary of op-amp behavior**

V+ = V I+ = I = 0 Seems strange, but the input terminals to an op-amp act as a short and open at the same time

7
**To analyze an op-amp circuit**

Write node equations at + and - terminals (I+ = I = 0) Set V+ = V Solve for Vout

8
**Inverting configuration**

Very popular circuit

9
**Analysis of inverting configuration**

I1 = (Vi - V)/R1 I2 = (V - Vo)/R2 set I1 = I2, (Vi - V )/R1 = (V - Vo)/R2 but V = V+ = 0 Vi /R1 = -Vo/R2 Solve for Vo I2 I1 Gain of circuit determined by external components Vo/ Vi = -R2/R1

10
**Summing Amplifier Current in R1, R2, and R3 add to current in Rf**

(V1-V)/ R1 + (V2-V)/ R2 + (V3-V)/R3 = (V - Vo)/ Rf Set V = V+ = 0, V1/ R1 + V2/ R2 + V3/ R3 = Vo / Rf solve for Vo, Vo = - Rf(V1 / R1 + V2 / R2 + V3 / R3) V1 V2 V3 R1 R2 R3 Rf This circuit is called a weighted summer

11
**To analyze an op-amp circuit**

Write node equations at + and - terminals (I+ = I = 0) Set V+ = V Solve for Vout

12
Integrator I1 = (Vi - V)/R1 I2 = set I1 = I2, (Vi - V)/R1 = but V- = V+ = 0 Vi/R1 = Solve for Vo I2 I1 Output is the integral of input signal. CR1 is the time constant

13
**Noninverting configuration**

(0 - V)/R1 = (V - Vo)/R2 But, Vi = V+ = V , (- Vi)/ R1 = (Vi - Vo)/R2 Solve for Vo, (- Vi)/R1 - (-Vi)/R2 = (-Vo)/R2 Vi (1/R1+ 1/R2) = (Vo)/R2 Vo = Vi (R2/R1+ R2/R Vi I Vo = Vi(1+R2/R1)

14
Buffer amplifier Isolates input from output Vi = V+ = V = Vo Vo = Vi

15
**Analyzing op-amp circuits**

Write node equations using: V+ = V I + = I = 0 Solve for Vout Usually easier, can solve most problems this way. Write node equations using: op amp model. Let A infinity Solve for Vout Works for every op-amp circuit. OR

16
**Difference amplifier Use superposition, set V1 = 0, solve for Vo**

(noninverting amp) set V2 = 0, solve for Vo (inverting amp)

17
Difference amplifier V2 R4/(R3+R4) V02 = (1 + R2/R1) [R4/(R3+R4)] V2

18
Difference amplifier V01 = -(R2/R1)V1

19
Add the two results V0 = V01 + V02 If R1 = R2 = R3 = R4

20
**Design of difference amplifiers**

For Vo = V2 - V1 Set R2 = R1 = R, and set R3 = R4 = R For Vo = 3V2 - 2V1 Set R1 = R, R2 = 2R, then 3[R4/(R3+R4)] = 3 Set R3 = 0

Similar presentations

OK

CHAPTER 20 OPERATIONAL AMPLIFIERS (OP-AMPS). Introduction to operational amplifiers Symbol and Terminals.

CHAPTER 20 OPERATIONAL AMPLIFIERS (OP-AMPS). Introduction to operational amplifiers Symbol and Terminals.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on biogas in india Ppt on operation research in linear programming Ppt on power quality and energy management Ppt on eddy current probes Ppt on air pollution for class 6 Ppt on fine dining etiquette Ppt on p&g products images Download ppt on turbo generator images Ppt on our environment for class 10th free download Ppt on water scarcity definition