Exam-style question
Try this first
In a non‑inverting amplifier, why does the output not invert the phase of the input signal?.
- A.Because the op‑amp is ideal.
- B.Because the input is applied to the non‑inverting terminal and negative feedback keeps the difference zero.
- C.Because the feedback resistor is very large.
- D.Because the supply voltage is high.
Model answer
What a good answer should say
- Because the input is applied to the non‑inverting terminal and negative feedback keeps the difference zero.
Explanation
Why this works
Initial state: V_in is applied to the + input; V_out is unknown. Step‑by‑step execution: 1.
The op‑amp amplifies the difference between its inputs. 2.
Negative feedback connects V_out to the − input, forcing the op‑amp to adjust V_out until the voltage at the − input equals the voltage at the + input. 3.
This equality means the output follows the input without a sign change. Final state: V_out has the same polarity as V_in.
Conclusion: The combination of a non‑inverting input and negative feedback prevents phase inversion.
Common mistake
No common mistake is linked to this question yet.