Analog and electronic circuits

What does an inverting amplifier do when several inputs are connected through resistors to its inverting input?

  1. AOutputs the product of the input voltages
  2. BCompares the sizes of the input voltages
  3. COutputs the weighted sum of the input voltages (with inverted sign)
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Answer: C. Outputs the weighted sum of the input voltages (with inverted sign)

Because the inverting input is a virtual ground, the currents flowing in from each input through its resistor add together and flow through the feedback resistor. The output is Vout = −Rf (V1/R1 + V2/R2 + …), a weighted sum. This is called an inverting summing amplifier.

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