Question:medium

For an ideal op-amp, what is the output voltage if the feedback resistance is equal to the input resistance in an inverting configuration?

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Inverting amplifier gain: $A_v = -\frac{R_f}{R_{in}}$
If $R_f = R_{in}$ → Gain = $-1$
Updated On: Mar 17, 2026
  • $V_o = V_{in}$
  • $V_o = -V_{in}$
  • $V_o = 0$
  • $V_o = 2V_{in}$
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The Correct Option is B

Solution and Explanation

Understanding the Question: We are asked for the output voltage of an inverting amplifier when the input and feedback resistors are the same.
Key Formulas and approach: The output voltage $V_o$ for an inverting amplifier is: \[ V_o = -\left( \frac{R_f}{R_{in}} \right) V_{in} \] Detailed Solution:
Step 1: Given values. We are told that the feedback resistance ($R_f$) equals the input resistance ($R_{in}$). So, $R_f = R_{in}$.
Step 2: Calculating the Gain. \[ \text{Gain} = -\frac{R_f}{R_{in}} = -\frac{R_{in}}{R_{in}} = -1 \] Step 3: Final Result. Since the gain is $-1$, the output voltage $V_o$ is $(-1) \times V_{in}$.
Conclusion: $V_o = -V_{in}$.
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