Question

The output of differential gain is given by _________

(a) (difference of the two input voltage)*(feedback resistance/input resistance)

(b) (sum of the two input voltage)*(feedback resistance/input resistance)

(c) (difference of the two input voltage)*(input resistance/feedback resistance)

(d) (sum of the two input voltage)*(input resistance/feedback resistance)

I have been asked this question during an interview.

I'd like to ask this question from Sources of Noise in Low Level Measurements topic in chapter Recording System of Biomedical Instrumentation

Answer 1

The correct option is (a) (difference of the two input voltage)*(feedback resistance/input resistance)

Easiest explanation: The output of differential gain is given by (difference of the two input voltage)*(feedback resistance/input resistance). gain is given by (feedback resistance/input resistance). The input resistances of but the inputs are the same.