This article mainly introduces the working principle and function of the diode. A diode is an electronic component with two electrodes that allows current to flow in only one direction. The most common use of a diode is rectification. The varicap diode is used as an electronic variable capacitor.

Most diodes have current unidirectionality, commonly known as rectification. The most common function of a diode is to allow current to flow in only one direction (called forward bias) and to block it in reverse bias. Therefore, a diode can be seen as an electronic check valve.

The working principle of a diode is based on the pn junction formed by p-type and n-type semiconductors. A space charge layer is formed on both sides of the interface, and a self-built electric field is established. When there is no external voltage, the diffusion current caused by the difference in carrier concentration on both sides of the pn junction and the drift current caused by the self-built electric field are equal and in a state of equilibrium.

When a forward bias voltage is applied to the diode, the external electric field and the self-built electric field cancel each other out, causing the diffusion current of the carrier to increase and resulting in a forward current. When a reverse bias voltage is applied, the external electric field and the self-built electric field are further strengthened, resulting in a reverse saturation current I0 that is independent of the reverse bias voltage value within a certain range of reverse voltage.

When the applied reverse voltage reaches a certain level, the electric field strength in the space charge layer of the pn junction reaches a critical value, and the carrier multiplication process occurs, generating a large number of electron-hole pairs and producing a large reverse breakdown current, which is called the breakdown phenomenon of the diode. The reverse breakdown of the pn junction can be divided into Zener breakdown and avalanche breakdown.

The diode is one of the most commonly used electronic components, and its biggest characteristic is unidirectional conductivity, which means that current can only flow through the diode in one direction. The functions of the diode include rectification circuits, detection circuits, voltage regulation circuits, and various modulation circuits, which are mainly composed of diodes. It is precisely because of the invention of diodes and other components that our rich and colorful electronic information world has emerged.

To test whether this component is normal, we only need to use a multimeter to measure the reverse resistance on the resistance range. If the reverse resistance is small, the diode is bad; if the reverse resistance is large, the diode is good. For such basic components, we should firmly grasp their working principles and basic circuits, so as to lay a good foundation for future electronic technology learning.

The above is an introduction to the working principle and function of the diode. I hope it will be helpful to everyone.