Structure and principle of photoresistor

Shunuo varistor / ESD varistor / product complete / Sunlord first-class agent

NCP18XH103F03RB MURATA Murata thermistor original spot

AVX tantalum capacitor low resistance TPSD107K016R0100 original 2011+

Photocoupler

A photoresistor is a device that uses a semiconductor photoconductive phenomenon to detect an optical signal. It may be a single crystal sheet, a polycrystalline sheet, a sintered polycrystalline film, a vacuum evaporation film, a chemical deposition film or a sputter film.
Photoresistors, also known as light guides, are almost always made of semiconductor materials. The structure and wiring diagram of the photoresistor are shown in Figure 9‐2.

When the photoresistor is irradiated with light, its conduction performance is enhanced by the internal photoelectric effect, and the resistance value is lowered, so that the current flowing through the load resistor RL and the voltage across it also change. The stronger the light, the higher the current and the lower the resistance. When the light stops, the photoelectric effect disappears and the resistance returns to its original value. If the photoresistor is connected to a closed loop, the current in the loop can be changed by changing the intensity of the illumination, and the optical signal can be converted into an electrical signal.
Photosensitive semiconductor materials include silicon, germanium, cadmium sulfide, lead sulfide, indium antimonide, and cadmium selenide. For a pure semiconductor that does not have luminescent properties, an appropriate amount of impurities can be added to produce photoelectric effect characteristics. The substances used to produce this effect are composed of metal sulfides, selenides, tellurides, etc., such as cadmium sulfide, lead sulfide, antimony sulfide, antimony sulfide, cadmium selenide, lead selenide, lead telluride, and the like. Photoresist applications depend on a range of characteristics such as dark current, photocurrent, volt-ampere characteristics of the photoresistor, illumination characteristics, spectral characteristics, frequency characteristics, temperature characteristics, and sensitivity of the photoresistor, time constant, and optimum operating voltage. .