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

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

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

CIRCUIT WITH OPERATIONAL AMPLIFIER LOAD DRIVING CIRCUIT OP-AMP

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

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

THE IDEAL OP-AMP

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!

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

LEARNING EXAMPLE

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-)

LEARNING EXAMPLE: DIFFERENTIAL AMPLIFIER IDEAL OP-AMP CONDITIONS NODES @ INVERTING TERMINAL NODES @ NON INVERTING TERMINAL

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

LEARNING EXTENSION

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

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