Exam-style question
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In a non‑inverting amplifier, if the input voltage is +2 V, what will be the polarity of the output?.
- A.+2 V
- B.-2 V
- C.0 V
- D.+4 V
Model answer
What a good answer should say
- +2 V
Explanation
Why this works
Initial state: V_in = +2 V, V_out unknown. Step‑by‑step execution: 1.
The input is applied to the + input. 2.
Negative feedback forces the op‑amp to adjust V_out until the voltage at the − input equals +2 V. 3.
The op‑amp therefore drives V_out to a positive value that satisfies the feedback equation. Final state: V_out is positive, matching the sign of V_in.
Conclusion: The output polarity is the same as the input polarity.
Common mistake
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