OpAmpspp2

# OpAmpspp2 - CIRCUITS WITH OPERATIONAL AMPLIFIERS Why do we...

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1 CIRCUITS WITH 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 COMMERCIAL PACKAGING OF TYPICAL OP-AMP OP-AMP ASSEMBLED ON PRINTED CIRCUIT BOARD LMC 6294 DIP PIN OUT FOR LM324 DIMENSIONAL DIAGRAM LM 324

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2 CIRCUIT SYMBOL FOR AN OP-AMP LINEAR MODEL OUTPUT RESISTANCE INPUT RESISTANCE GAIN 7 5 12 5 10 10 : 50 1 : 10 10 : A R R O i TYPICAL VALUES CIRCUIT WITH OPERATIONAL AMPLIFIER DRIVING CIRCUIT LOAD OP-AMP MANUFACTURER PART No A Ri[MOhm] Ro[Ohm] National LM324 100,000 1 20 National LMC6492 50,000 10 150 Maxim MAX4240 20,000 45 160 COMMERCIAL OP-AMPS AND THEIR MODEL VALUES
3 CIRCUIT AND MODEL FOR UNITY GAIN BUFFER 0 = + + + in O O i s V A I R I R V : KVL 0 = + + in O O V A I R out V - : KVL I R V i in = : VARIABLE G CONTROLLIN i O O i s out R A R R V V + + = 1 1 SOLVING 1 S out O V V A WHY UNIT GAIN BUFFER ? BUFFER GAIN PERFORMANCE OF REAL OP-AMPS Op-Amp BUFFER GAIN LM324 0.99999 LMC6492 0.9998 MAX4240 0.99995 = A ) ( 0 + = = v v A v R O O THE IDEAL OP-AMP = i R = = = A R R i O , , 0 IDEAL + i i

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4 THE VOLTAGE FOLLOWER OR UNITY GAIN BUFFER s v v = + + = v v = v v O S O v v = CONNECTION WITHOUT BUFFER CONNECTION WITH BUFFER S O v v = THE VOLTAGE FOLLOWER ACTS AS BUFFER AMPLIFIER THE SOURCE SUPPLIES POWER THE SOURCE SUPPLIES NO POWER THE VOLTAGE FOLLOWER ISOLATES ONE CIRCUIT FROM ANOTHER ESPECIALLY USEFUL IF THE SOURCE HAS VERY LITTLE POWER LOOP ANALYSIS IS NOT VERY CONVENIENT CAVEATS LEARNING EXAMPLE s out V V G = GAIN THE DETERMINE
LEARNING EXAMPLE s out V V G = GAIN THE DETERMINE 0 = + v 0 = = = + v v v A o 0 = v 0 = = = + i i R i 0 0 0 2 1 = + R V R V out s - v @ KCL APPLY 0 = i 1 2 R R V V G s out = = NEXT WE EXAMINE THE SAME CIRCUIT WITHOUT THE ASSUMPTION OF IDEAL OP-AMP THINK NODES! REPLACING OP-AMPS BY THEIR LINEAR MODEL

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OpAmpspp2 - CIRCUITS WITH OPERATIONAL AMPLIFIERS Why do we...

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