Question

If the differential voltage gain and the common mode voltage gain of the differential amplifier are 48 dB and 2 dB respectively, then its common mode rejection ratio is:

• A. 23 dB
• B. 25 dB
• C. 46 dB
• D. 50 dB

Hint:

CMRR is a measure of how well a differential amplifier rejects common mode signals. It is the difference between the differential gain and the common mode gain.

Answer 1

The Correct Option is C

The common mode rejection ratio (CMRR) is defined as the ratio of the differential voltage gain ($A_d$) to the common mode voltage gain ($A_{cm}$), expressed in decibels (dB): \[ CMRR = A_d - A_{cm} \] Given:
- Differential voltage gain, $A_d = 48 \text{ dB}$
- Common mode voltage gain, $A_{cm} = 2 \text{ dB}$
Substitute these values into the CMRR formula: \[ CMRR = 48 \text{ dB} - 2 \text{ dB} = 46 \text{ dB} \] Thus, the common mode rejection ratio is 46 dB.