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Explain the Basic Circuit of Differential Amplifier

      

Explain the Basic Circuit of Differential Amplifier

  

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Wilfred
- Fig. 7.4(i) shows the basic circuit of a differential amplifier. It consists of two transistors Q1 and Q2 that have identical (ideally) characteristics. They share a common positive supply VCC, common emitter resistor RE and common negative supply VEE. Note that the circuit is symmetrical.
- Fig. 7.4(ii) shows the symbol of differential amplifier. The following points may be noted about the differential amplifier:
(i) The differential amplifier (DA) is a two-input terminal device using at least two transistors. There are two output terminals marked 1 (vout 1) and 2 (vout 2).
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(ii) The DA transistors Q1 and Q2 are matched so that their characteristics are the same. The collector resistors (RC1 and RC2) are also equal. The equality of the matched circuit components makes the DA circuit arrangement completely symmetrical.
(iii) We can apply signal to a differential amplifier (DA) in the following two ways:
(a) The signal is applied to one input of DA and the other input is grounded. In that case, it is called single-ended input arrangement.
(b) The signals are applied to both inputs of DA. In that case, it is called dual-ended or double-ended input arrangement.
(iv) We can take output from DA in the following two ways:
(a) The output can be taken from one of the output terminals and the ground. In that case, it is called
single-ended output arrangement.
(b) The output can be taken between the two output terminals (i.e., between the collectors of Q1 and Q2). In that case, it is called double-ended output arrangement or differential output.
(v) Generally, the differential amplifier (DA) is operated for single-ended output. In other words, we take the output either from output terminal 1 and ground or from output terminal 2 and ground. Any input/output terminal that is grounded is at 0V.

Wilfykil answered the question on August 15, 2019 at 13:30


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