Yanling (Shanghai) Technology Co., LTD

There are many differences between transistor BJT and FET, a few simple lists:

1. Transistor current control, MOS tube belongs to voltage control, BJT amplifies the current, FET converts the gate voltage to drain current. The first parameter of BJT is current amplification factor β, and the first parameter of FET is broken conduction gm.

2. Driving capacity: MOS tube common power switch tube, and large current local switch circuit;

3. Cost problem: transistor is cheap, MOS is expensive;

4. BJT linearity is poor, FET linearity is good;

5. BJT noise is larger, FET noise is smaller;

6. BJT polarity is only NPN and PNP two types, FET polarity has N channel, P channel, as well as depletion type and enhanced type, so the selection and use of FET are more complicated;

7. Power consumption problem: BJT input resistance is small, large current consumption, FET input resistance is large, almost no current consumption;

In fact, the transistor is relatively cheap, easy to use, commonly used in digital circuit switch control; MOS tubes are used in high frequency high-speed circuits, high current situations, and where base or drain control current is more sensitive.

In general, whether in discrete component circuits or integrated circuits, FET replacement of BJT is a big trend.