Exam-style question
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Which component in a summing amplifier determines the weighting of each input signal?.
- A.The feedback resistor
- B.The input resistors
- C.The op-amp's supply voltage
- D.The non-inverting input bias resistor
Model answer
What a good answer should say
- The input resistors
Explanation
Why this works
Formula: Vout = -(Rf/R1)V1 -(Rf/R2)V2 ... Substitution: R1, R2, V1, V2 are the input resistor values and input voltages.
Working: Each input voltage is divided by its resistor, multiplied by the feedback resistor, and summed with a negative sign. Answer: The input resistors set the weighting (gain) of each input signal.
Units: volts. Conclusion: They determine the gain of each input signal.
Common mistake
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