Question:
A difference amplifier is shown in the figure. Assume the op-amp to be ideal. The CMRR (in dB) of the difference amplifier is (rounded off to 2 decimal places).
A difference amplifier is shown in the figure. Assume the op-amp to be ideal. The CMRR (in dB) of the difference amplifier is (rounded off to 2 decimal places).
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For ideal op-amps, ensure accurate resistor matching to achieve high CMRR values.
Updated On: Feb 3, 2026
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Correct Answer: 39.5 - 41.5
Solution and Explanation
Step 1: Calculate the differential and common-mode gains. The differential gain is: \[ A_d = \frac{R_f}{R_g}. \] The common-mode gain is: \[ A_c = \frac{\Delta R}{2 R_{avg}}, \] where \( R_{avg} = \frac{R_1 + R_2}{2} \) and \( \Delta R \) is the mismatch.
Step 2: Calculate the CMRR. The CMRR in dB is: \[ \text{CMRR} = 20 \log_{10} \left( \frac{A_d}{A_c} \right). \] After substituting values: \[ \text{CMRR} = 39.50 \, \text{to} \, 41.50 \, \text{dB}. \]
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