Exam-style question
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If the feedback resistor in a summing amplifier is increased while keeping input resistors constant, what happens to the output voltage for a given set of input signals?.
- A.It increases proportionally
- B.It decreases proportionally
- C.It remains unchanged
- D.It becomes non-linear
Model answer
What a good answer should say
- It increases proportionally
Explanation
Why this works
Formula: Vout = -(Rf/Ri)V. Substitution: Rf increased, Ri constant.
Working: The ratio Rf/Ri increases, so the magnitude of Vout increases proportionally. Answer: It increases proportionally.
Units: volts. Conclusion: Larger feedback resistor increases gain.
Common mistake
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