What is a phototransistor, the principle, characteristics, and testing methods of phototransistors

Phototransistor is a device used for photoelectric conversion, which can convert optical signals into electrical signals. Its characteristics are simple structure, high sensitivity, fast response speed, and easy use. Widely used in fields such as optoelectronic communication, optoelectronic measurement, and optoelectronic control.

1、 The principle of phototransistor

The principle of the SN65176BDR phototransistor is based on the photoelectric effect.   When the photon energy is greater than the bandgap width of the semiconductor, the photon is absorbed, which excites the electron and hole pairs in the semiconductor, forming electron hole pairs. These electron hole pairs will be separated by an electric field, forming a current, namely photocurrent.

A phototransistor is a PNP type semiconductor device composed of a base region, an emitter region, and a collector region. When the emission region is illuminated by light, photons are absorbed and excited into electron hole pairs, which move towards the collector and base regions respectively, forming an electric current. At this point, a large number of charge carriers are injected into the base region, forming a PN junction reverse bias, thereby increasing the current amplification factor.

2、 Characteristics of phototransistor

1. High sensitivity: The sensitivity of phototransistors is higher than that of photodiodes and photodiodes, which can provide higher photoelectric conversion efficiency.

2. Fast response speed: The response speed of phototransistors is faster than that of photodiodes and photodiodes, enabling faster signal transmission.

3. Good stability: Phototransistors have better stability than photodiodes and photodiodes, and can be used over a wider temperature range.

4. Widely used in circuits: Phototransistors can be used as key components in circuits such as photoelectric converters, photoelectric amplifiers, and photoelectric switches.

3、 Testing methods for phototransistors

The testing methods for phototransistors mainly include photocurrent testing and photoresistor testing.

1. Photocurrent test: Aim the light source at the emission area of the phototransistor and measure the photocurrent of the phototransistor. The magnitude of photocurrent is directly proportional to the intensity of the light source and is related to the sensitivity of the phototransistor.

2. Photoresistor test: Place the phototransistor in the dark, measure its resistance value, then aim the light source at the emitting area of the phototransistor, measure its resistance value again, and calculate the photoresistor of the phototransistor. The size of a photoresistor is inversely proportional to the sensitivity of a phototransistor.

The above is a brief introduction to the principle, characteristics, and testing methods of phototransistors. Phototransistor is an important photoelectric conversion device with a wide range of applications and high technical content, which requires reasonable selection and use in practical applications