Phototransistor is a semiconductor device that can convert optical signals into electrical signals. It is a kind of photosensitive element based on common transistor structure and a photoelectric converter, also known as EP2S90F1020I4N Photosensitive triode. The photoelectric triode has the basic structure of an ordinary triode, but a photosensitive material is added to the base region, so that it can respond to light and convert light signals into electrical signals. Phototransistor is usually used in photoelectric control, photoelectric measurement, photoelectric detection and other fields.
1、 Structure and working principle of phototransistor
The structure of photoelectric triode is basically the same as that of ordinary triode, including a base, an emitter and a collector. Different from the ordinary triode, the phototransistor adds photosensitive materials in the base region, so that it can respond to light and convert light signals into electrical signals.
The working principle of phototriode is basically the same as that of ordinary triode, except that under light, electrons and holes will be excited after photons are absorbed, which will change the concentration of electrons and holes, thus changing the conductivity of the base region. When the base of the phototransistor receives light, electrons and holes are excited, and recombination occurs in the base region, which changes the conductivity of the base region. The change of conductivity will affect the change of collector current and emitter current, thus realizing the conversion of optical signal to electrical signal.
2、 Classification of phototriodes
Phototransistor can be divided into silicon phototransistor, germanium phototransistor and GaAs phototransistor according to different photosensitive materials. Among them, silicon phototransistor and germanium phototransistor are the two most common phototransistors.
1. Silicon phototransistor
Silicon phototransistor is a kind of photosensitive element based on silicon transistor structure. The photosensitive material of silicon phototriode is usually silicon, which has low sensitivity and slow response speed, but is relatively cheap. It is widely used in some low frequency, low-speed photoelectric control, measurement and detection fields.
2. Germanium phototransistor
Germanium phototransistor is a kind of photosensitive element based on germanium transistor structure. The photosensitive material of germanium phototransistor is usually germanium, which has high sensitivity and fast response speed, but is expensive. Germanium phototransistor is widely used in some high frequency, high-speed photoelectric control, measurement and detection fields.
3、 Characteristics of phototransistor
1. High sensitivity: photoelectric triode has high sensitivity and can respond to weak optical signals.
2. Fast response speed: photoelectric triode has a fast response speed and can respond to optical signals in microseconds.
3. Wide linear range: photoelectric triode has a wide linear range and can respond linearly to the intensity of different optical signals.
4. Good stability: photoelectric triode has good stability and can maintain good performance under different environmental conditions.
5. Easy integration: photoelectric triode has various packaging forms, which is easy to integrate into other circuits.
4、 Application of Phototransistor
1. Photoelectric control: Photoelectric triode can convert optical signals into electrical signals, which can be used for the photoelectric control function of the circuit.
2. Photoelectric measurement: Photoelectric triode can efficiently convert optical signals, and can be used in the field of photoelectric measurement.
3. Photoelectric detection: Photoelectric triode can respond linearly to the intensity of different light signals, and can be used in the field of photoelectric detection.
4. Photoelectric amplification: Photoelectric triode can amplify weak light signals, which can be used in the field of photoelectric amplification.
5. Photoelectric isolation: Photoelectric triode can realize the photoelectric isolation function of the circuit and can be used in some special circuit designs.
5、 Test methods for phototriodes
1. Photocurrent test
Photocurrent test is the most basic test method of photoelectric triode, which can be used to detect the sensitivity and response speed of devices. During the test, the light source is irradiated on the photosensitive area of the phototransistor to measure the output photocurrent. The photocurrent is proportional to the intensity of the light source, and the sensitivity of the phototransistor can be tested by changing the intensity of the light source. The response speed can be evaluated by measuring the rise time and fall time of photocurrent.
2. Photovoltage test
Photovoltage test is a method to measure the output voltage of phototransistor, which can be used to detect the linearity and voltage gain of devices. During the test, the light source is illuminated in the photosensitive area of the phototransistor, and the output photovoltage is measured. The light voltage is proportional to the intensity of the light source. The linearity and voltage gain of the phototransistor can be measured by changing the intensity of the light source.
3. Noise test
Noise test is a method to test the noise index of photoelectric triode, which can be used to evaluate the signal-to-noise ratio and noise level of devices. During the test, the light source is irradiated in the photosensitive area of the phototransistor to measure the output noise voltage or noise current. The noise voltage or noise current is independent of the intensity of the light source. The noise performance of the device can be evaluated by measuring the noise level of the phototransistor.
6、 Development Trend of Phototransistor
1. High speed
With the development of communication technology, the demand for high-speed photoelectric conversion devices is becoming higher and higher. As a high-speed photoelectric converter, photoelectric triode has the advantage of fast response, and will be widely used in high-speed communication, optical fiber communication and other fields.
2. High sensitivity
The sensitivity of phototransistor is an important index to evaluate its photoelectric conversion efficiency. With the continuous development of science and technology, the requirements for high sensitivity of photoelectric conversion devices are becoming higher and higher. Therefore, future phototransistors will pay more attention to improving their sensitivity to meet the needs of different fields.
3. Low power consumption
Low power consumption is an important development direction of optoelectronic conversion devices in the future. With the development of new technologies such as intelligence and the Internet of Things, the demand for low power consumption is becoming more and more urgent. In the future, photoelectric triodes will pay more attention to reducing power consumption to meet the needs of different fields.
4. Miniaturization
With the continuous development of integrated circuit technology, the demand for miniaturized devices is growing. The future photoelectric triode will pay more attention to miniaturization to meet the needs of various special applications.
7、 Summary
Phototriode is a semiconductor device that can convert optical signals into electrical signals. Its structure and working principle are basically the same as those of ordinary triodes, but photosensitive materials are added to the base area to enable it to respond to light and convert optical signals into electrical signals. Phototransistor has the characteristics of high sensitivity, fast response, wide linear range, good stability and easy integration, and is widely used in photoelectric control, photoelectric measurement, photoelectric detection, photoelectric amplification, photoelectric isolation and other fields.
