1 9. Design of Multiple-input Op. Amp. Circuits 9.1Operational AmplifiersOperational Amplifiers 9.2Basic Operational Amplifier CircuitsBasic Operational Amplifier Circuits 9.3Input resistance of Op. Amp. AmplifiersInput resistance of Op. Amp. Amplifiers 9.4Multiple-Input Operational Amplifier CircuitMultiple-Input Operational Amplifier Circuit 9.5Design of Multiple-Input AmplifiersDesign of Multiple-Input Amplifiers

EE Electronics Circuit Design 9.1Operational Amplifiers output +V cc -V cc +V cc -V cc Inverting Input (-) Non- InvInput (+) Inverting Input (-) output Op. Amp. input Impedance Very high Differential Amplifier Emitter Constant current source Collector Constant current source Output Impedance very low Push-pull Emitter follower at the output Non Inverting Input (+) Therefore Operational Amplifier has (1)very high input impedance, R i =  (or) i i = 0 (2) very high voltage gain A v = 10 5 (or) v + = v - (3) very low output impedance R 0 = 0 Amplifier voltage gain very high + - i i = 0 v + = v - R 0 = 0

EE Electronics Circuit Design 1. INVERTING AMPLIFIER 2. NON-INVERTING AMPLIFIER 9.2Basic Operational Amplifier Circuits

EE Electronics Circuit Design 3. VOLTAGE FOLLOWER 4. INVERTING SUMMING AMPLIFIER

EE Electronics Circuit Design 6. NON-INVERTING SUMMER 5. DIFFERENTIAL AMPLIFIER

EE Electronics Circuit Design 8. OP. AMP. INTEGRATOR 7. OP. AMP. DIFFERENTIATOR

EE Electronics Circuit Design Examples Find V o of the following Op. Amp. circuits

EE Electronics Circuit Design Find V o of the followings Op. Amp. circuits Find I L of the followings Op. Amp. circuits

EE Electronics Circuit Design Inverting amplifiers R i Non-inverting amplifiers R i 9.3Input resistance of Op. Amp. amplifiers

EE Electronics Circuit Design 9.4Multiple-Input Operational Amplifier Circuit To derive a general design table for given V o of Multiple-Input Op. Amp. Circuit:- 1.Find V - from the input voltages V a ---V m 2.Find V + from the input voltages V a ---V n 3.Equate V + and V - and find the V o 4.Make equal dc path resistance at both input terminals of Op. Amp. 5.Assign coefficient and make design table Multiple-Input Operational Amplifier circuit

EE Electronics Circuit Design 9.5Design of Multiple-Input Amplifier

EE Electronics Circuit Design 1. Find V - from the input voltages V a ---V m

EE Electronics Circuit Design 2. Find V + from the input voltages V 1 ---V n

EE Electronics Circuit Design 3. Equate V + and V - and find the V o

EE Electronics Circuit Design 4.Design of the multiple coefficients

EE Electronics Circuit Design 5.Design table R1R1 R2R2

EE Electronics Circuit Design Summary of Design Equations Multiple-Input Amplifier According to V o equation, multiple input op. amp. circuit is drawn first with positive term resistors plus standard R X at “ n-inv ” terminal then with negative term resistors plus standard R Y at “ inv ” terminal. Add standard R F CaseZRYRY RXRX R i (n-inv)R j (inv) IIZ < 0  - R F / ZR F / X i R F / Y j 1. Assume given V O = -10V 2 + 5V 1 2. Draw circuit with one resistor (R 1 ) for +5V 1 and one standard R X at “ n-inv ” terminal. 3. Continue with one resistor (R 2 ) for – 10V 2 and one standard R Y at “ inv ” terminal. 4. Add feedback resistor R F. 7. Find resistor ratio5. Find Z 6. Use Design Table

EE Electronics Circuit Design 8. Find R F from required type and value of resistance at input terminal of the op. Amp. Assume required min 10k  at Op. Amp. Input terminal. 9. Now we can find R X, R 1 and R 2 by using R F =100k 10. Finally draw the circuit with designed values V O = -10V 2 + 5V 1

EE Electronics Circuit Design Design Example-1 H.W. 2.1 (LECTURE) Design an op. Amp. Circuit to implement the equation V o =4V 1 +V 2 -8V a -6V b. Design with lowest resistance at any input terminal of the op. Amp = 10k  CaseZRYRY RXRX R i (n-inv) R j (inv) IIZ < 0  - R F / ZR F / X i R F / Y j

EE Electronics Circuit Design Design an Op. Amp. Circuit with a minimum resistance 10k  and the output V O = -100V X +50V Y.. Design with Superposition Method. Design Example-2 (conventional method) The circuit is differential Op. Amp. Circuit as the output contain one positive term and one negative term and derive V o equation.

EE Electronics Circuit Design Design an Op. Amp. Circuit with a minimum resistance 10k  and the output V O = -100V X +50V Y.. Design with Multiple input design method. Design Example-3 (multiple input design method) According to V o equation, it is multiple input op. amp. circuit with one input at “ inv ” terminal (for -100V X ) and another at “ n-inv ” terminal (for +50V Y ). Standard R X and R Y are included first. CaseZRYRY RXRX R i (n-inv) R j (inv) IIZ < 0  - R F / ZR F / X i R F / Y j

EE Electronics Circuit Design EXAMPLE 2.5 (PAGE 51-TEXT) Design an op. Amp. Circuit to implement the equation V o =4V 1 +V 2 -8V a -6V b. Design with equal DC path resistance = 10k  Design Example-4 CaseZRYRY RXRX R i (n-inv)R j (inv) IIZ < 0  - R F / ZR F / X i R F / Y j

EE Electronics Circuit Design Design Example-5 EXAMPLE 2.5 (PAGE 51-TEXT) Design an op. Amp. Circuit to implement the equation V o =4V 1 +V 2 -8V a -6V b. Design with highest resistance of 200k  at any input terminal except feedback resistor R F CaseZRYRY RXRX R i (n-inv) R j (inv) IIZ < 0  - R F / ZR F / X i R F / Y j