Photosensitive resistance are special resistors made of semiconductor materials such as cadmium sulfide or cadmium selenide, which are very sensitive to light. When there is no light, they are in a high-resistance state, the dark resistance is generally up to 1.5MΩ. With the development of science and technology, the special properties of photosensitive resistance have been widely used. The differences between it and photosensitive diode are as follows:
1. Different functions
Photosensitive resistance uses the optical properties of semiconductor materials and other materials to realize the function of variable resistance, while photosensitive diode uses the optical properties of semiconductor materials to realize the switching function of diodes.
2. Different materials
Although sometimes the same materials such as silicon and gallium arsenide are used for both, the material range of photosensitive resistance is wider than that of photosensitive diodes.
3. Different parameters
Photosensitive resistance: nominal resistance, use environment temperature (maximum operating temperature), measured power, rated power, nominal voltage (maximum operating voltage), operating current, temperature coefficient, material constant, time constant, etc.
photosensitive diode: the highest operating voltage, dark current, photocurrent, photoelectric sensitivity, response time, junction capacitance and forward voltage drop, etc.
4. Different structure
The photosensitive resistance only needs two electrodes, while for the photosensitive diode, a PN junction is required to be formed between the two electrodes, and in order to increase the conduction current, the area of one electrode is designed to be large and the other is relatively small.