Analog and electronic circuits

Which circuit converts a photodiode current into a voltage by feeding the current into the inverting input of an op-amp and converting it with a feedback resistor?

  1. AIntegrator
  2. BComparator
  3. CTransimpedance amplifier (current-to-voltage converter)
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Answer: C. Transimpedance amplifier (current-to-voltage converter)

In a transimpedance amplifier, the inverting input is a virtual ground, so all the input current flows through the feedback resistor, and the output voltage is −(input current × feedback resistance). It is used to convert tiny photodiode currents into voltages in optical receivers and light sensors.

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