The main parameters of the semiconductor diode

Lead-in: In semiconductor diodes, do you know which parameters are represented by IR, IF, IO, IFSM, VRM, VR, fM, Trr, P in semiconductor diodes? Here we come to understand one by one.

1. Reverse saturation leakage current IR

Refers to the current flowing through the diode when a reverse voltage is applied across the semiconductor diode. This current is related to the semiconductor material and temperature. At room temperature, the IR of the silicon tube is in the order of 10A to 10A, and the IR in the helium tube is in the order of 10A to 10A.

2. Rated rectifier current IF

Refers to the average current value converted from the allowed temperature rise when the diode is operated for a long period of time. At present, the IF value of a high power rectifier diode can reach 1000A.

3. Maximum average rectified current IO

In a half-wave rectifier circuit, the maximum value of the average rectified current flowing through the load resistor. This is a very important design value.

4. Maximum Inrush Current IFSM

Excessive forward current allowed to flow. It is not a normal current but an instantaneous current. This value is quite large.

5. Maximum reverse peak voltage VRM

Even if there is no reverse current, as long as the reverse voltage is constantly increased, the diode will be damaged sooner or later. This reverse voltage, which can be added, is not the instantaneous voltage, but is the positive and negative voltage repeatedly added. Since the AC voltage is applied to the rectifier, its maximum value is an important factor. The maximum reverse peak voltage VRM refers to the maximum reverse voltage that can be applied to avoid breakdown. The current highest VRM value can reach several thousand volts.

6. Maximum DC reverse voltage VR

The above-mentioned maximum reverse peak voltage is the peak voltage repeatedly added, and VR is a value when the DC voltage is continuously applied. For DC circuits, the maximum DC reverse voltage is very important for determining the allowable value and the upper limit value.

7. Maximum operating frequency fM

Due to the junction capacitance of the PN junction, its unidirectional conductivity deteriorates when the operating frequency exceeds a certain value. Point-contact diodes have higher fM values ​​above 100MHz; rectifier diodes have lower fM, typically no more than a few kilohertz.

8. Reverse recovery time Trr

When the operating voltage changes from the forward voltage to the reverse voltage, the ideal condition for the operation of the semiconductor diode is that the current can be turned off instantaneously. In fact, it usually takes a little delay. Determine the amount of current cut-off delay is the reverse recovery time. Although it directly affects the switching speed of the diode, it does not necessarily mean that the value is small. That is, when the diode is abruptly reversed by conduction, the reverse current is greatly attenuated to a time close to IR. When the high-power switch operates in the high-frequency switching state, this indicator is of utmost importance.

9. Maximum power P

The current flowing through the diode will absorb heat and increase its temperature. The maximum power P is the maximum power. Specifically, the voltage across the diode is multiplied by the current flowing through it. This limit parameter is particularly important for zener diodes and variable resistance diodes.

Source: Chongqing Electronic Technology Co., Ltd.