The characteristics of field effect transistor and triode

Features of FETs and triodes:

1. The source s, gate g, and drain d of the FET correspond to the emitter e, base b, and collector c of the triode, respectively. Their functions resemblance.

2. The FET is a voltage-controlled current device, iD is controlled by vGS, and its amplification factor gm is generally small, so the FET has poor amplifying ability; the triode is a current Control current devices, iC is controlled by iB (or iE).

3. The gate of the FET takes almost no current (ig»0); while the base of the triode always draws a certain current. Therefore, the input resistance of the FET is higher than that of the triode.

4. The FET has only the majority of the carriers involved in conduction; the triode has both the carrier and the minority involved in the conduction, and the minority concentration is greatly affected by factors such as temperature and radiation, so The FET has better temperature stability and stronger radiation resistance than the transistor. Field effect transistors should be selected when the environmental conditions (temperature, etc.) vary greatly.

5. When the source water of the FET is connected to the substrate, the source and drain can be used interchangeably, and the characteristics change little; When electrodes and emitters are used interchangeably, their characteristics are very different, and the b-value will decrease a lot.

6. The noise figure of the FET is very small, and the FET should be used in the input stage of the low noise amplifier circuit and the circuit requiring a high signal-to-noise ratio.

7. Field effect transistors and triodes can be used to form various amplifier circuits and open circuit circuits, but because the former has a simple manufacturing process, low power consumption, good thermal stability, and The advantages of wide power supply voltage range, etc., are widely used in large-scale and very large-scale integrated circuits.

8. The on-resistance of the triode is large, and the on-resistance of the field effect transistor is small, only a few hundred milliohms. In the current electrical devices, the field effect transistor is generally used. Switch is used, its efficiency is relatively high .