The difference between photodiode and phototransistor

Second, the structure principle of the photodiode

The photodiode housing has a glass lens, which can be directly injected into the die through the lens. The die of the photodiode is a pn junction with photosensitive properties.

The photosensitive surface of the photodiode die is a thin film layer formed on n-type single crystal silicon by diffusion technology. The pn junction area between the photodiode die and the core is large, the electrode area of the core one is small, and the depth of the pn junction is generally shallow for semiconductor diodes to improve the photoelectric conversion function.

In addition, like ordinary semiconductor diodes, the SiO2 protective layer is embedded in the silicon wafer to protect the edge of the pn junction, improve the stability of the photodiode, and reduce dark current.

Third, the difference between photodiodes and phototransistors

There are two differences between photodiodes and phototransistors. The first difference is that the outer packaging is different. There are two types of outer packaging for photodiodes, namely plastic packaging and mechanically sealed packaging, while the packaging of phototransistors is only plastic packaging. The second difference is the different voltage. Because phototransistors are upgraded versions of photodiodes, the voltage of phototransistors will be larger and the use effect will be better. However, the voltage of phototransistors in a dark environment is higher than that of photodiodes, so be careful when choosing.