Question

Which of the following statement is true for an instrumentational amplifier?

(a) the input resistance of both the inputs is very high and does not change as the gain is varied

(b) the input resistance of both the inputs is very low and does not change as the gain is varied

(c) the input resistance of both the inputs is very high and does  change as the gain is varied

(d) the input resistance of both the inputs is very low and does  change as the gain is varied

I have been asked this question during an online interview.

I want to ask this question from Biomedical Signal Analysis and Processing Techniques topic in division Recording System of Biomedical Instrumentation

Answer 1

Right choice is (a) the input resistance of both the inputs is very high and does not change as the gain is varied

The best I can explain: The input resistance of both the inputs is very high and does not change as the gain is varied in and instrumentational amplifier.  Voltage gain from differential input (V1–V2) to single ended output, is set by one resistor. V0 does not depend on common-mode voltage, but only on their difference.