1. OPERATIONAL AMPLIFIERS
Why do we study them at this point???
1. OpAmps are very useful electronic components
2. We have already the tools to analyze practical circuits
using OpAmps
3. The linear models for OpAmps include dependent sources
TYPICAL DEVICE USING OP-AMPS

2. LM324 DIP LMC6294 MAX4240 OP-AMP ASSEMBLED ON PRINTED CIRCUIT BOARD
APEX PA03
DIMENSIONAL DIAGRAM LM 324
PIN OUT FOR LM324

3. CIRCUIT SYMBOL FOR AN OP-AMP SHOWING POWER SUPPLIES
OUTPUT RESISTANCE
INPUT RESISTANCE
GAIN
LINEAR MODEL
TYPICAL VALUES

4. CIRCUIT WITH OPERATIONAL AMPLIFIER
LOAD
DRIVING CIRCUIT
OP-AMP

5. TRANSFER PLOTS FOR SOME COMERCIAL OP-AMPS
SATURATION
REGION
LINEAR
IDENTIFY SATURATION REGIONS
OP-AMP IN SATURATION

6. CIRCUIT AND MODEL FOR UNITY GAIN BUFFER
WHY UNIT GAIN BUFFER?
PERFORMANCE OF REAL OP-AMPS
BUFFER
GAIN

7. THE IDEAL OP-AMP

8. THE UNITY GAIN BUFFER – IDEAL OP-AMP ASSUMPTION
PERFORMANCE OF REAL OP-AMPS
USING LINEAR (NON-IDEAL) OP-AMP MODEL WE OBTAINED
IDEAL OP-AMP ASSUMPTION YIELDS EXCELLENT APPROXIMATION!

9. WHY USE THE VOLTAGE FOLLOWER OR UNITY GAIN BUFFER?
THE VOLTAGE FOLLOWER ACTS AS
BUFFER AMPLIFIER
THE VOLTAGE FOLLOWER ISOLATES ONE
CIRCUIT FROM ANOTHER
ESPECIALLY USEFUL IF THE SOURCE HAS
VERY LITTLE POWER
CONNECTION WITHOUT BUFFER
CONNECTION WITH BUFFER
THE SOURCE SUPPLIES NO POWER
THE SOURCE SUPPLIES POWER

10. LEARNING EXAMPLE

11. THINK NODES! LEARNING EXAMPLE: DIFFERENTIAL AMPLIFIER
KCL AT V_ AND V+ YIELD TWO EQUATIONS
(INFINITE INPUT RESISTANCE IMPLIES THAT i-, i+ ARE KNOWN)
THE OP-AMP IS DEFINED BY ITS 3 NODES. HENCE IT NEEDS 3 EQUATIONS
OUTPUT CURRENT IS NOT KNOWN
DON’T USE KCL AT OUTPUT NODE. GET THIRD EQUATION FROM INFINITE
GAIN ASSUMPTION (v+ = v-)

12. LEARNING EXAMPLE: DIFFERENTIAL AMPLIFIER
IDEAL OP-AMP CONDITIONS
INVERTING TERMINAL
NON INVERTING TERMINAL

13. USE REMAINING NODE EQUATIONS FINISH WITH INPUT NODE EQUATIONS…
LEARNING EXAMPLE: USE IDEAL OP-AMP
USE REMAINING NODE EQUATIONS
FINISH WITH INPUT NODE EQUATIONS…
USE INFINTE GAIN ASSUMPTION
ONLY UNKWONS ARE OUTPUT NODE VOLTAGES
6 NODE EQUATIONS + 2 IDEAL OP-AMP

14. LEARNING EXTENSION

15. “inverse voltage divider”
LEARNING EXTENSION
NONINVERTING AMPLIFIER - IDEAL OP-AMP
SET VOLTAGE
INFINITE GAIN ASSUMPTION
INFINITE INPUT RESISTANCE
“inverse voltage divider”

16. LEARNING EXAMPLE
UNDER IDEAL CONDITIONS BOTH CIRCUITS SATISFY
DETERMINE IF BOTH IMPLEMENTATIONS PRODUCE THE
FULL RANGE FOR THE OUTPUT
EXCEEDS SUPPLY VALUE.
THIS OP-AMP SATURATES!
POOR IMPLEMENTATION