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What is the difference between a triode and a FET?

Why do you choose a triode or FET in the circuit? There are so many advantages of FETs. Why can't they completely replace the triodes?
The FET is also a semiconductor device with a PN junction. It uses the effect of the electric field to control the current, hence the name. In addition to the characteristics that the input terminal does not take current substantially, it has the advantages of being easy to integrate and less affected by radiation and temperature. Divided into two types of junction type and insulated grid type. Used for expansion, vibration, switching circuits, especially for circuits with high input impedance requirements.

Ordinary triodes, also called bipolar transistors, use a small current to control large currents and are a current control component. It is used for general high frequency and low frequency signal expansion, vibration and switching circuits.

What is the difference between the triode and the FET?
1. The FET is very fast. The on-resistance of the low-voltage FET can now be 2 milliohms (of course not all tubes), which means that the current of 10A is also the voltage drop of 20mV. The voltage drop is 0.2-0.3V, and the power consumption is very different, so the switching power supply is commonly used.
2. The drive of the FET is simple (voltage type) without requiring speed.
3. The FET is sensitive to voltage. The probability of overvoltage damage is larger than that of the transistor. This is a disadvantage. When using a relay, the transistor is relatively reliable (anti-back pressure).