Exam-style question
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In an inverting amplifier circuit, the output voltage is 180° out of phase with the input voltage. Explain why this phase inversion occurs.
Model answer
What a good answer should say
- Because the input is applied to the inverting terminal of the op‑amp, the negative feedback forces the output to change in the opposite direction to keep the inverting node at the same potential as the non‑inverting node.
- A positive change at the input therefore produces a negative change at the output, giving a 180° phase shift.
Explanation
Why this works
The answer shows understanding of the virtual short and negative feedback in an inverting amplifier, and explains how the sign of the gain leads to phase inversion. It tests knowledge of op‑amp behaviour and phase relationships.
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