Q. Four strain gauges in a Wheatstone bridge configuration are connected to an instrumentation amplifier as shown in the figure. From the choices given below, the preferred value for the common mode rejection ratio (CMRR) of the amplifier, in dB, would be
Ans: 100
Sol:
CMRR of an amplifier is given by
Where Ad is differential mode gain
ACM is common mode gain.
For an ideal instrumentation amplifier CMRR is infinity but practically it is very large.
From the given options, 100 dB is the most proffered value.
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