What are the main functions of resistors, capacitors, diodes and triodes in the circuit?

Diodes are unidirectional conductive elements used in AC circuits. Four diodes can be used to form a full-bridge rectifier, so that the AC power supply equipment has positive and negative poles. Two diodes can be used to form a half-bridge rectifier circuit to increase the current. Light-emitting diodes are light-emitting elements and are also polar. When connected to a specified voltage, the LED can light up. They are usually used for lighting and reminding the working state of electrical appliances. It can also be connected in series to form a negative electrode and a parallel positive electrode, and several pins are connected in a logic circuit to display a display matrix on electrical equipment for displaying machine codes and various graphics, or it can be formed into a photoelectric coupler, which is composed of light-emitting diodes and photoresistors or phototransistors. Light-emitting diodes can illuminate photosensitive devices, so that the resistance of photosensitive devices decreases when they are irradiated by light, forming such a condition. In the power supply and the circuit to be controlled, the high-voltage circuit and the low-voltage circuit are separated, which is convenient for control and detection. The zener diode can automatically release the voltage and the over-limit voltage, which can make the voltage exceed the rated range too much, and then the zener diode will directly conduct short circuit, so that the due voltage will be short-circuited to the ground to achieve the purpose of protection, or the conducted voltage can directly drive the thyristor to conduct, and use this condition to control other precision power consumption. The capacitance requirements of circuit protection and varactor diode are different at different voltages. Different capacitors can make the frequency change under different capacitors, so that the frequency can be adjusted humanely to achieve the required purpose. It is often used in TV tuners and radios. Different diodes used in the circuit have different characteristics. The frequency of voltage requires the diode to have good conductivity. And recovery characteristics. Without these characteristics, the life of diode will die, so we should pay special attention to these technical indicators in maintenance and application! Diode; A person who lacks dialectical thinking