• In today’s article, we are going to study about ‘ differential-amplifier ‘ How beneficial it is and what is the basics of differential amplifier you should know before getting a detailed information on it. And hence We will also read about some more topics like single ended output, single ended input, double ended input, double ended output, common mode signal, differential mode signal etc given in Detail.  So, take your notebooks in you hand and get ready to study physics in an easy and sorted way.


A differential-Amplifier is a circuit that can accept two input signal And amplify the difference between these two input signal.

We can apply signal to the differential amplifier in two ways,

1) Single ended input– When signal is applied on only one Input and other input is grounded, this is called single ended input differential amplifier.

2) Dual ended/ double ended input– When signal are applied on both two input then these type of differential amplifier is called dual/ double ended input amplifier.

We can take output from the differential amplifier in following two ways,

  1. If we take output from one end and other terminal will be ground these type of differential amplifier is called single ended output differential amplifier.
  2. Double ended output- The Output can be taken between two Output terminal this is called double ended output differential amplifier.

Note- Generally differential amplifier is operated for single ended output.

Operating of Differential amplifier

Differential amplifier


The following points are noting about the single ended input differential amplifier-

  1. When signal is applied to input one and if we get Output from one then it will be inverted. Or we can say that 180° phase or on the other hand if we get Output amplified in same phase (360° phase). Reserve is happening when signal is applied to input two and input one is grounded (fig 1 and fig 2) where Output is two.
  2. When only one output terminal is available the phase of single ended input differential amplifier depends on which input receive the Input signal. Here Output always in same phase (in phase) with respect to input. As shown in fig (3) and (1).

Common mode and differential mode signal-

We know that in the differential amplifier we get the Output of the differential of two input i.e. called differential amplifier. In the differential amplifier we give the Input into two ways,

  1. Common mode signal
  2. Differential mode signal

( DJ- differential mode→ negative feedback)

1.)Common mode signal-

When both input signal are in same phase and having exactly equal amplitude, they are called common mode signal. Common mode signal are not amplified (rejected) by the differential amplifier. It is because differential amplifier, amplify the difference between two signal (v1- v2). And for common mode signal the difference will be zero.

2) Differential mode signal-

When the Input signal are in 180° out off phase. And exactly equal in amplitude they are called Differential mode signal. The differential mode signal are amplified by the differential amplifier, it is because difference in signal is twice the value of each signal.

Differential mode input-

Common mode Input-


So our article is finished and after completely reading this article, one can easily tell what is differential amplifier. And we have also discussed some more topics like basics of differential amplifier, single ended output, single ended input, double ended input, double ended output, common mode signal, differential mode signal etc

‌So one can say that they got a detailed information about differential amplifier and basic information about other topics.

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