Optical Sensors - Phototransistors

Phototransistors are light sensitive semiconductor devices that are typically used as an output signal source in various optical sensing systems. They are also used for analog voltage or current applications as a way to detect an input signal directly from a light source. The common PT381 model of phototransistor is among the most popular devices used in these applications for multiple reasons, such as its robustness, low price, and ease of understanding in terms of its application and working principle.

Application Field of the PT381

In optical sensing systems, the PT381 finds its use in multiple different and distinct applications. It can be used in bi-directional optical switching and modulating, as it is capable of sensing light at different wavelengths and intensities. This ability has made it suitable for building optical sensors that can detect changes in both distance and objects using wavelengths in the visible and non-visible (infrared) spectrums. Additionally, the PT381 is suitable for most imaging applications due to its strong photoelectric characteristics. PT381 phototransistors can detect signals quickly and accurately in power control systems, enabling stronger and more effective responses for various scenarios.

Working Principle of the PT381

In terms of its working principle, the PT381 phototransistor is based on photoelectricity, which is a phenomenon where unaffected electrons naturally flow in a vacuum tube or semiconductor when exposed to light or ultraviolet radiation. When the light strikes the base section of the phototransistor, the electrons in the base region become excited and travel to the collector region. This movement of electrons across the collector and the base regions creates an electric current, which acts as an output signal for the phototransistor. This type of output signal can then be used in various types of optical sensing applications, such as optical distance and object detection.

Conclusion

The PT381 is a popular type of phototransistor used in optical sensing systems due to its robustness, low price, and ease of understanding. Its application field ranges from bi-directional optical switching and modulating to most imaging applications. Additionally, its working principle is based on photoelectricity, where light or ultraviolet radiation excites electrons in its base region and generates an electrical current in its collector region, which is then used as an output signal in the sensing system.