How does a transimpedance amplifier convert current into voltage?

How does a transimpedance amplifier convert current into voltage?

• A. The input current is applied to the noninverting input with a resistor in the feedback path.
• B. The input current is injected into the inverting input and a feedback resistor converts it to a voltage.
• C. The input current is injected into the noninverting input and a feedback network converts it.
• D. The output is independent of input current.

Answer: (C)

A transimpedance amplifier converts current to voltage by using an op-amp with a feedback resistor from the output back to the inverting input. The noninverting input is tied to a reference (usually ground). The op-amp’s high gain drives its output so that the inverting input sits at approximately the same voltage as the noninverting input, creating a virtual ground at the summing junction. Because of that, the input current must flow through the feedback resistor, which converts it into a voltage at the output. The output voltage equals minus the input current times the feedback resistance: Vout = -If × Rf (the sign depends on current direction). This is the essence of how a transimpedance amplifier performs current-to-voltage conversion.

A transimpedance amplifier converts current to voltage by using an op-amp with a feedback resistor from the output back to the inverting input. The noninverting input is tied to a reference (usually ground). The op-amp’s high gain drives its output so that the inverting input sits at approximately the same voltage as the noninverting input, creating a virtual ground at the summing junction. Because of that, the input current must flow through the feedback resistor, which converts it into a voltage at the output. The output voltage equals minus the input current times the feedback resistance: Vout = -If × Rf (the sign depends on current direction). This is the essence of how a transimpedance amplifier performs current-to-voltage conversion.