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Transimpedance amplifier
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ToggleThe 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](https://sp-ao.shortpixel.ai/client/to_auto,q_glossy,ret_img,w_310,h_232/https://learnchannel-tv.com/wp-content/uploads/2024/04/Transimpedance-amplifier.png)
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](https://sp-ao.shortpixel.ai/client/to_auto,q_glossy,ret_img,w_763,h_355/https://learnchannel-tv.com/wp-content/uploads/2024/04/Op-Amp-as-Transimpedance-amplifier-exercise.png)
Op-Amp as Transimpedance amplifier - exercise
- What tasks do these two Op-Amp´s have in this circuit?
- 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?
- In the diagram below, add the characteristic curve V1 depending on the sensor signal!
![Op-Amp as Transimpedance amplifier - diagrams](https://sp-ao.shortpixel.ai/client/to_auto,q_glossy,ret_img,w_605,h_491/https://learnchannel-tv.com/wp-content/uploads/2024/04/Op-Amp-as-Transimpedance-amplifier-diagrams.png)
Op-Amp as Transimpedance amplifier - diagrams
1. Op-Amp 1 as transimpedance - Converter, Op-Amp 2 as summer
2. Current signal can also be kept constant or stable via a long signal line. Minimum current 4 mA means wire break protection.
3. See diagram below:
![](https://sp-ao.shortpixel.ai/client/to_auto,q_glossy,ret_img,w_249,h_299/https://learnchannel-tv.com/wp-content/uploads/2024/04/Op-Amp-as-Transimpedance-amplifier-solution.png)
Op-Amp as Transimpedance amplifier - solution