Question

Which amplifier will reject any common mode signal that appears simultaneously at both amplifier input terminal and amplifies only the voltage difference that appears across its input terminals?

(a) ac coupled amplifiers

(b) differential amplifiers

(c) carrier amplifiers

(d) dc amplifiers

I have been asked this question by my school principal while I was bunking the class.

Enquiry is from Preamplifiers topic in division Recording System of Biomedical Instrumentation

Answer 1

Right answer is (b) differential amplifiers

The best I can explain: Differential amplifier is one which will reject any common mode signal that appears simultaneously at both amplifier input terminals and amplifies only the voltage difference that appears across its input terminals. Most of the amplifiers used for measuring bioelectric signals are of the differential type. AC amplifiers have a limited frequency response and are, therefore, used only for special medical applications such as electrocardiograph machine.