How to improve the switching speed of the transistor?

The switching time determines the switching speed of the transistor, which has an on and off process corresponding to the on time.

The turn-on time consists of delay time and rise time, while the turn off time is divided into storage time and fall time.

(1) Delay time

Delay time refers to the time it takes to charge the capacitor between the C and E poles, increasing the base current of the transistor and accelerating the charging speed of the base capacitor. However, if the base current is too high, it can cause the transistor to experience deep saturation, which in turn increases the storage time and the turn off time. Therefore, the base current needs to be selected appropriately.

(2) Rise time

The time required for a transistor to reach critical saturation is called the rising conduction time. Increase the base input current to saturate the collector current. Similarly, the base current should not be too large, otherwise it will prolong the storage time and result in an increased turn off time.

(3) Storage time

The time required for a transistor to transition from saturation state (collector positive bias) to critical saturation state (collector 0 bias) is called storage time. Shortening storage time can be achieved by increasing the current drawn from the base region and accelerating the discharge rate of excess stored charge.

(4) Descent time

The time from critical saturation to base voltage zero is called the descent time.

In summary, in order to reduce the switching time and improve the switching speed of the transistor, the following considerations can be made in the use of the transistor:

a. Increasing the base current can shorten the delay time, but excessive base current can lead to an increase in storage time

b. Increasing the base current can shorten the storage time and descent time

c. Acceleration capacitor