A differential amplifier has a differential gain A d of 100 and c
| A differential amplifier has a differential gain Ad of 100 and common mode gain Ac of 0.1. What is its CMRR?
A. 10 dB
B. 20 dB
C. 30 dB
D. 60 dB
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Right Answer is: D
SOLUTION
Concept:
CMRR (Common mode rejection ratio) is defined as the ratio of differential-mode voltage gain (Ad) and the common-mode voltage gain (Ac).
Mathematically, in dB this is expressed as:
\(CMRR = 20\log \left| {\frac{{{A_d}}}{{{A_c}}}} \right| \)
Calculation:
Given Ad = 100
Ac = 0.1
\(CMRR = 20\log_{10} \left| {\frac{{{100}}}{{{0.1}}}} \right|~dB\)
\(CMRR = 20\log_{10} \left| {{{10^3}}} \right| ~dB\)
CMRR = 20×3 = 60 dB