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).
\includegraphics[width=0.5\linewidth]{61.png}
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).
\includegraphics[width=0.5\linewidth]{61.png}
\includegraphics[width=0.5\linewidth]{61.png}
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For ideal op-amps, ensure accurate resistor matching to achieve high CMRR values.
Updated On: Jan 23, 2025
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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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