About TVS transient suppression diode

About TVS transient suppression diode

TVS transistor is a transient suppression diode, which is a semiconductor device with surge absorption capability; The zener diode uses the PN junction to keep the reverse breakdown voltage basically unchanged, but the current can change within a certain range. It has a High impedance before the reverse breakdown voltage, and it will be in a low resistance state beyond this critical point.

The Electronic symbol of zener diode and TVS diode is basically the same as that of zener diode, and the packaging is also similar. Sometimes it is difficult to tell which is which in appearance

The main differences between voltage regulator diodes and TVS diodes are as follows:

1. Circuit connection method

The zener diode and TVS diode are connected in reverse in the circuit, that is, by using its reverse characteristics and the Avalanche effect of the PN junction, there is a critical voltage before reverse breakdown. Both of them have the stabilizing effect in the reverse access circuit, but they are different. The zener diode uses to fix the input voltage at a certain value, while the TVS diode mainly prevents the transient high voltage from clamping the subsequent circuit;

2. Response time

Zener diodes generally do not talk about response time, but rather focus on the zener value. However, for TVS diodes, their characteristics determine that they have different effects. TVS diodes have transient suppression and high energy effects, so it is required to absorb higher energy in a short time, so this time is very short, reaching the nanosecond level;

3. Power size

The power of a  transient suppression diode is generally not very high. Common voltage regulator diodes include 1W, 2W, etc. Its power is determined by the allowed temperature rise, and in fact, it is the product of stable voltage and current. For example, for a voltage regulator diode 1N4742A, its maximum power is only 1W, and the voltage regulator value is 12V. Therefore, the current passing through it should not exceed 80mA, otherwise the tube will heat up severely; For TVS diode, it pays attention to the instantaneous Pulsed power. This power value is very high, reaching up to kilowatts, but this time value remains very small.