Question

In an inverting op-amp, the voltage gain is

• A. \(+\dfrac{R_f}{R_{in}}\)
• B. \(-\dfrac{R_{in}}{R_f}\)
• C. \(-\dfrac{R_f}{R_{in}}\)
• D. \(+\dfrac{R_{in}}{R_f}\)

Hint:

For an ideal inverting amplifier, \[ \boxed{ A_v=-\frac{R_f}{R_{in}} } \] The minus sign indicates phase inversion.

Answer 1

The Correct Option is C

Step 1: Recall the gain formula of an inverting amplifier. For an ideal inverting op-amp, \[ A_v=\frac{V_o}{V_i} = -\frac{R_f}{R_{in}}. \]

Step 2: Interpret the negative sign. The negative sign indicates that the output is \(180^\circ\) out of phase with the input. Hence, \[ \boxed{ A_v=-\frac{R_f}{R_{in}} } \] Therefore, \[ \boxed{(C)} \] is the correct answer.