The metal film resistor is a widely used resistor so far, and plays an important role in the field of electronic industry and military space where require high precision. The metal film resistor is made of a special metal or alloy through a method of vacuum evaporation or sputtering to form a resistive film layer on the ceramic or glass. This kind of resistor is generally made by a vacuum evaporation process, that is, the alloy is heated in a vacuum, and the alloy is evaporated to form a layer of conductive metal film on the surface of the porcelain rod. Compared with the carbon film resistor, the resistor has the advantages of small volume, low noise and good stability, but the cost is high. It is widely applied as a precision and high-stability resistor, and is also commonly used in various radio electronic devices.
Also, in an ideal resistor, the resistance will not change with the voltage or current, nor will the current change abruptly. The real resistor cannot achieve this. Today's internal design allows resistors to exhibit relatively small variances at extreme voltages or currents. While the resistance for photoresistor vary greatly along with the light condition.
Photoresistor is also a widely used resistor. It is a special resistor made of semiconductor materials such as sulfid or selenide. Its working principle is based on the internal photoelectric effect. The stronger the light intensity is, the lower the resistance value is. With the increase of light intensity, the resistance value decreases rapidly, and the bright resistance value can be lower than 1KΩ.
Photoresistor is a semiconductor photo sensor. In addition to its high sensitivity, fast reaction speed, good spectral characteristics and good consistency of r value, it can also maintain a high degree of stability and reliability under the harsh environment of high temperature and humidity. It can be widely used in camera, solar courtyard lamp, lawn lamp, banknote detector, quartz clock, mini night lamp, light and sound control switch and so on.
No matter what kind of resistor, its development direction is miniaturization, high reliability, high stability, etc. In order to adapt to the development of circuit integration and planarization, the need for chip resistor will obviously increase. The general-purpose type will tend to develop thick-film resistors, while the precision ones will still tend to metal film resistors and metal foil resistors.
