Closed-loop gain from resistor ratio — A feedback amplifier has a feedback/input resistor ratio RFB/RIN = 4.6 and is driven at the noninverting (+) input with 1.7 V. Assuming a standard noninverting configuration in linear operation, what is the output voltage?

Introduction:
For a noninverting amplifier, the closed-loop gain depends on the feedback network ratio. Correctly mapping the stated “feedback/input resistor ratio” to the noninverting gain expression ensures accurate output predictions and avoids misinterpreting saturation or cutoff conditions when rails are not specified.

Given Data / Assumptions:

• Noninverting configuration
• RFB/RIN = 4.6
• Vin (+ input) = 1.7 V
• Ideal op-amp, linear range (supply rails wide enough)

Concept / Approach:

The closed-loop gain for the noninverting amplifier is Av = 1 + (RFB / RIN). Multiply this by the input voltage to obtain the output voltage, provided the result is within supply rails and the amplifier remains unsaturated.

Step-by-Step Solution:

Verification / Alternative check:

Rearrange to check: Vin = Vout / Av = 9.52 / 5.6 = 1.7 V, confirming consistency.

Why Other Options Are Wrong:

• 7.82 V: Uses an incorrect gain factor.
• saturation / cutoff: No evidence of rail limits or biasing to force nonlinearity.
• 4.6 V: Misreads the ratio as the gain itself and ignores the “+1” term.

Common Pitfalls:

• Forgetting the “+1” in the noninverting gain formula.
• Confusing RFB/RIN with RIN/RFB.

Final Answer:

9.52 V