Classified by volt-ampere characteristics
For most conductors, the resistance of a conductor remains almost constant at a certain temperature, and this type of resistance is called linear resistance. The resistance of some materials varies significantly with current (or voltage), and their volt-ampere characteristics are a curve, and this type of resistance is called a nonlinear resistance. Nonlinear resistance: At a given voltage (or current), the ratio of voltage to current is the quiescent resistance at that operating point, and the slope on the volt-ampere characteristic curve is the dynamic resistance. The way to express the nonlinear resistance characteristics is complex, but these nonlinear relations are widely used in electronic circuits.
Classification by material
a. Wire-wound resistors are made of resistive wires wound into resistors made of high-resistance alloy wires wound on an insulating skeleton, and the outside is coated with a heat-resistant glaze insulation layer or insulating varnish. The winding resistor has a low temperature coefficient, high resistance accuracy, good stability, heat and corrosion resistance, and is mainly used for precision high-power resistors, but the disadvantage is that the high-frequency performance is poor and the time constant is large.
b. Carbon synthetic resistors are made of carbon and synthetic plastics.
c. The carbon film resistor is made by coating a layer of carbon on the porcelain tube, and depositing the crystalline carbon on the ceramic rod skeleton. Carbon film resistors are the most widely used resistors due to their low cost, stable performance, wide resistance range, low temperature coefficient and voltage coefficient.
d. The metal film resistor is made by coating a layer of metal on the porcelain tube, and the alloy material is evaporated on the surface of the ceramic rod skeleton by vacuum evaporation.
The metal film resistor has higher precision, better stability, less noise and less temperature coefficient than the carbon film resistor. It is widely used in instrumentation and communication equipment.
e. The metal oxide film resistor is made by plating a layer of tin oxide on the porcelain tube, and depositing a layer of metal oxide on the insulating rod. Because it is an oxide, it is stable at high temperatures, resistant to thermal shock, and has a strong load capacity According to the application, there are general, precision, high-frequency, high-voltage, high-resistance, high-power and resistance networks.