Non-inverting op-amp gain control (clarified without a diagram): For a non-inverting amplifier with input resistor Rin from the inverting input to ground and feedback resistor Rf from output to inverting input, the closed-loop voltage gain is Av = 1 + (Rf / Rin). Which change increases the amplifier's voltage gain magnitude?

Introduction / Context:
Without a schematic, it is easy to confuse which resistor controls gain in a non-inverting operational-amplifier stage. This item restates the standard configuration and asks which component change raises the closed-loop voltage gain. The answer relies on the canonical formula for the non-inverting gain.

Given Data / Assumptions:

• Non-inverting op-amp: input applied to the + node.
• Feedback network: Rf from output to − input, Rin from − input to ground.
• Closed-loop gain Av = 1 + (Rf / Rin), ideal op-amp behavior assumed.

Concept / Approach:
Because Av depends on the ratio Rf / Rin, the gain increases if Rf increases or if Rin decreases. Changing the input signal amplitude does not change the gain; it only changes output level proportionally. Scaling Rf and Rin together by the same factor leaves the ratio unchanged, so Av stays the same.

Step-by-Step Solution:

Verification / Alternative check:
Pick numerical values (e.g., Rf = 90 kΩ, Rin = 10 kΩ → Av = 10). Double Rf to 180 kΩ → Av = 19; halve Rin to 5 kΩ → Av = 19. The gain rises in both cases.

Why Other Options Are Wrong:
Decrease Rin: would also be correct in principle, but this option is not listed as the answer; however, increasing Rf is a direct, unambiguous method selected as correct here.
Increase input amplitude: changes output level but not the gain setting.
Decrease both by the same factor: ratio unchanged, so gain unchanged.

Common Pitfalls:
Confusing inverting vs non-inverting formulas; ignoring how bias currents and noise may influence practical component choices.

Final Answer:
Increase Rf while keeping Rin constant