Working principle and category of crystal diodes 6

2. Reverse characteristic testing

Touch the red probe of the multimeter to the positive terminal of the diode and the black probe to the negative terminal of the diode. If the pointer is at or near infinity, the tube is qualified.

Diode applications

1. Rectifier diode

By utilizing the unidirectional conductivity of diodes, alternating alternating current can be converted into pulsating direct current in a single direction.

2. Switching element

Under the action of forward voltage, the resistance of a diode is very small and it is in a conducting state, equivalent to a turned on switch; Under the action of reverse voltage, the resistance is very large and in a cut-off state, like a disconnected switch. By utilizing the switching characteristics of diodes, various logic circuits can be formed.

3. Limiting element

After the diode conducts in the forward direction, its forward voltage drop remains basically unchanged (0.7V for silicon tubes and 0.3V for germanium tubes). By utilizing this characteristic, as a limiting element in the circuit, the signal amplitude can be restricted within a certain range.

4. Relay diode

Plays a relay role in the inductance of switch mode power supplies and inductive loads such as relays.

5. Detector diode

Plays a detection role in the radio.

6. Varactor diode

Used in high-frequency heads for televisions