Question

What should be CMRR of preamplifier upto 5 Khz?

(a) 10 dB

(b) 30 dB

(c) 90 dB

(d) greater than 90 dB

The question was posed to me in an internship interview.

I'd like to ask this question from Measurement of Respiration Rate topic in division Patient Monitoring System of Biomedical Instrumentation

Answer 1

Correct option is (d) greater than 90 dB

For explanation I would say: The common-mode rejection should be greater than 90 dB up to 5 kHz. A calibrating square wave signal of 100 mV (peak-to-peak) at a frequency of 100 Hz is usually available. The main amplifier has controls for gain adjustment from 5 mV/div to 10 mV/div for selecting the sensitivity most appropriate to the incoming signal from the patient.