![Op amp phototransistor circuit](https://kumkoniak.com/83.jpg)
The characteristics of a phototransistor are discussed below.
![op amp phototransistor circuit op amp phototransistor circuit](http://design.stanford.edu/spdl/ME218b/pastprojects/0708/killerkoala/links/circuits_files/image001.gif)
The graph below shows the magnitude of current increases along with the intensity of light. The energy of light drops on the junction of the collector to base then it generates the majority charge carriers and adds the flow of current toward the reverse saturation current. Whenever no light ray drops on the transistor’s surface, then a little reverse saturation current will induce on top of the phototransistor due to the fewer minority charge carriers. The junction of the emitter-base is connected in forwarding bias whereas the collector-base region is connected in the reverse biased.
![op amp phototransistor circuit op amp phototransistor circuit](https://i.stack.imgur.com/lQi7n.png)
Earlier, germanium and silicon materials are used for constructing this phototransistor. The construction of the phototransistor is quite similar to the ordinary transistor. At last, the arrangement of a phototransistor can be done in a metallic box & a lens is placed at the top of the box to absorb the incident radiation.
![Op amp phototransistor circuit](https://kumkoniak.com/83.jpg)