# Identification and function of electronic components on circuit board

Time：

2022-12-02 15:56

In general circuits, common code identifications are as follows:
R --- Resistance
C ---- Capacitor
D --- Diode
VT --- triode, or FET
L --- Inductance
W --- Potentiometer
Z ---- Impedance
1. Resistance
The resistance is represented by "R" and numbers in the circuit. For example, "R7" represents the resistance numbered 7. The main functions of the resistance in the circuit are shunt, current limiting, voltage dividing, bias, filtering (combined with capacitors), impedance matching, etc.
There are two main methods to identify resistance:
Digital scale method: mainly used for small circuits such as patch
Color scale method: usually used for color ring resistor
2. Capacitance
Capacitance is generally represented by "C" and numbers in the circuit. Capacitance is a component composed of two metal films close together and separated by insulating materials. The characteristic of capacitor is mainly to isolate direct current and alternating current.
Capacitance is identified by two methods, namely, color coding method and number coding method.
3. Diode
Diodes are usually represented by "D" and numbers in the circuit, for example, D9 represents a diode with a number of 9. The main characteristic of diode is unidirectional conductivity, that is, under the action of forward voltage, the conduction resistance is very small; Under the action of reverse voltage, the on resistance is extremely large or infinite.
It is easy to identify the diode. The polarity of the diode can be determined directly by the symbol "P" and "N"; The positive and negative poles of the LED can be identified from the length of the pin. The long pin is positive, and the short pin is negative.
4. Triode
The triode is usually represented by "Q" plus a number in the circuit, for example, Q3 represents the triode with a number of 3. The triode is a special device with two PN junctions and amplification capability.
The arrangement of triode pins has certain rules. When the plane is facing its own state, there are e, b, and c pins from left to right, which are easy to identify.
5. Inductance
Inductance is usually represented by "L" plus a number in the circuit. For example, L10 refers to the inductance numbered 10. Inductance coil is made by winding insulated wires on the insulated skeleton for a certain number of turns.
Inductance identification generally includes direct marking method and color marking method, which are similar to resistance.