Differential Input and Differential Output Amplifier:
In almost all the applications, the op-amp is employed with a single-ended or unbalanced output. However, there are certain applications in which a differential output is desired. The differential input and differential output amplifier is widely employed as a pre-amplifier and in driving push-pull arrangements.
One possible arrangement of a differential input and differential output amplifier is given in Fig. 34.51. This circuit makes use of two identical op-amps.
Using the superposition theorem we have
Differential output voltage,
The above equation reveals that the input and output are in phase or are of the same polarity provided that vin = vin1 – vin2 and vout = vout1 – vout2.
The circuit given in Fig 34.51 is very useful in noisy environments, especially if the input signal is comparatively smaller. This is because it rejects the common-mode noise voltages.