Non-inverting amplifier sizing (numerical): A non-inverting op-amp has a closed-loop gain Av = 10. What input voltage is required to obtain an output of 3.43 V (assume linear operation and no saturation)?

Introduction / Context:
Non-inverting op-amp stages are common whenever a designer needs a precise, positive gain with high input impedance. Sizing the input for a desired output is a straightforward application of the closed-loop gain formula. This problem reinforces the relationship between output, gain, and input amplitude.

Given Data / Assumptions:

• Closed-loop gain Av = 10 (dimensionless voltage gain).
• Desired output Vout = 3.43 V.
• Linear region of operation: the op-amp is properly powered and not saturating.

Concept / Approach:
For a non-inverting amplifier, Vout = Av * Vin. Therefore, the input required is Vin = Vout / Av. With Av fixed at 10, this is a single-step division. The options are in millivolts to encourage correct unit handling.

Step-by-Step Solution:

Verification / Alternative check:
Back-calculate: 343 mV * 10 = 3.43 V, confirming the arithmetic and units.

Why Other Options Are Wrong:
400 mV, 480 mV, 600 mV produce outputs of 4.00 V, 4.80 V, and 6.00 V respectively at Av = 10, which do not match the target 3.43 V.

Common Pitfalls:
Mixing up Av = 1 + (Rf/Rin) with the direct scaling Vout = Av * Vin; forgetting to convert between volts and millivolts; ignoring headroom limits which can matter in real hardware but do not affect this arithmetic.

Final Answer:
343 mV