# Transimpedance amplifier

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### Transimpedance amplifier

The following circuit, which is referred to as a current-voltage converter or transimpedance converter (TIA), converts an input current IIN into a defined output voltage VOUT:

Transimpedance amplifier

The basis of the current-voltage converter is the inverting amplifier. Since the input current of the OP-Amp is negligibly small, we derive from the node rule:

IIN = - If

Applying the law of Ohm:

VOUT = Vf = If × Rf = - IIN × R

This makes it clear that the output voltage is proportional to the input current. The ratio of input current to output voltage is determined by the resistance Rf.

#### Exercise Op-Amp as Transimpedance Amplifier

Below you can see an Op-Amp circuit that converts a sensor signal of 4 ... 20 mA into a voltage signal of 0 to 10 V.

Op-Amp as Transimpedance amplifier - exercise

1. What tasks do these two Op-Amp´s have in this circuit?
2. What advantage does a sensor with a current signal of 4 to 20 mA offer compared to a sensor with a voltage signal of 0 to 10 V?
3. In the diagram below, add the characteristic curve V1 depending on the sensor signal!

Op-Amp as Transimpedance amplifier - diagrams