Op-Amp as Summing Amplifier
Category: Operational Amplifier
Designer: RANA MUHAMMAD ADNAN KHALIL
Notes
This circuit is designed and simulated in Proteus 7.10. In this circuit you will learn how operational amplifier (op-amp) is used as summing amplifier. 1. The op-amp used in this circuit is LM837, and it is in inverting amplifier configuration. 2. Before understanding this circuit, it is recommened to understand previous circuit "Op-Amp as Inverting Amplifier" in Operational Amplifier category. 3. The positive input of op-amp is grounded via 10k ohm resistor (R1). 4. The three input signals are given via 10k ohm resistors R2, R3 and R3. 5. The feedback resistor R5 of 10k ohm is used to maintain unity gain of each signal which is R5/R2, R5/R3 and R5/R4. 6. The output voltage is the sum of all the input signals present at inverting input of op-amp as shown in animation. 7. The output voltage signal is Vo = -(R5/R2 + R5/R3 + R5/R4), the negative sign is because it is in inverting amplifier configuration. 8. When both switch S1 and S2 are open then input signal at R2 and R3 is zero and only 2V signal is present at input R4, the output is -2V. 9. When any of switch is closed, then their input voltage will add, when switch S1 is closed 1.5V are added to output and output voltage become -(2+1.5)V = 3.5V. 10. When only S2 is closed then output voltage will be -(2+2.5)V = -4.5V. 11. When all the switches are closed then output voltage will be sum of all the input signals, which is -6V. Application: 1. This circuit can be used to generate descrete signals. 2. This circuit is used to understand the concept of summing amplifier. Note. More advance circuits will be added soon. So keep visiting EDAC app daily and share this app with your friends.