What are the differences between FETs and triodes?

2018-03-15

Field effect transistors are voltage controlled semiconductor devices. Transistor is a kind of semiconductor device that controls the current. Its function is to amplify the weak signal into an electrical signal with a larger amplitude and also used as a contactless switch. What are the differences between FETs and triodes? Let's take a look.


A field effect transistor (FET) is a type of semiconductor device that uses the electric field effect of the control input circuit to control the output circuit current. With this name, the characteristics of the field effect transistor are also determined. Because it conducts only majority carriers in the semiconductor, it is also called a unipolar transistor.


A transistor, which is one of the basic semiconductor components, has a current amplification function and is a core component of an electronic circuit. The triode is to make two PN junctions on a semiconductor substrate with short distances. The two PN junctions divide the whole semiconductor into three parts. The middle part is the base area and the two sides are the emitter area and the collector area. The arrangement method is PNP. And NPN two.

The following is the difference between FETs and triodes:


1, the triode is a bipolar tube, that is, when the tube is working, the interior is composed of two kinds of carriers: hole and free electron. Field effect tube is a unipolar tube, that is, when the tube is working, there is only hole, or only free electrons participate in conduction, there is only one kind of carrier;


2. The triode belongs to the current control device. Only when the input current has output current, the field effect transistor belongs to a voltage control device, and there is no input current but also an output current.


3, Lu crystal transistor input impedance is small, the input impedance of the FET is large;


4. The source and drain of some FETs may be interchangeable, and the collector and emitter of the transistor may not be interchangeable.


5. The frequency characteristics of Lujing FET are not as good as those of triodes;


6. The FET has a low noise figure and is suitable for preamplifiers of low noise amplifiers.


7. If you want a small signal source current, you should use a field effect transistor. Otherwise, use a triode.

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