Diffrential Amplifier using 3 opamps

1. Differential Amplifier
Using Three Op-Amps
Prepared by :
73. Rajat Shukla

2. Features Of Differential Amplifier with Three Op-Amps
• Very high input resistance
• Variable Voltage Gain
The advantages of the two differential amplifiers just
discussed can be combined in a single differential
amplifier having variable voltage gain and very high input
resistance. However, to achieve this desirable
combination, three op-amps must be used
Need of Differential Amplifier with Three Op-Amps

3. Circuit Diagram :

4. Voltage Gain :
Input Resistance :

5. Output Resistance :
where Ad = closed-loop gain of the differential
amplifier
Ro = output resistance of the op-amp
A = open-loop voltage gain of the op-amp
Remember that Ad is different for each of the
differential amplifier configurations.

6. Bandwidth :
As in the case of non inverting and inverting amplifiers, the
bandwidth of differential amplifiers also depends on the closed-
loop gain of the amplifier and is given by :
where fo is the open-loop break frequency of the op-
amp.

9. Thank You !