Fundamentals of Electronic Technology (III)_ Chapter 2 principle of amplification circuit__ Crystal triode and field effect triode

One Crystal triode

The crystal triode consists of two PN junction , Three electrodes

1. Structure and classification of crystal triodes , It has three districts , Two PN junction , Three electrodes are led out from the three areas to form .

（1） Three areas inside the crystal triode , They are called launch zones 、 Base area 、 Collector area .

（2） Electrodes led out respectively , The corresponding is called emitter (E)、 The base (B)、 Collector (C),

       E：emission,  B:basic,  C: collection

（3） Between the base area and the launch area PN A knot is called a launch knot , Between the base area and the collector area PN A junction is called a collector junction .

According to the doping form of the three regions, it can be divided into PNP Tube and NPN Two kinds of pipes ,

 

You can see , PNP type The arrow is on the inside , NPN Type is external .

  Arrow direction The current direction when the emitter junction is forward biased .

In this book , Usually made of silicon NPN For example, t-triode .

Two   Field effect triode

The crystal triode uses a small base current Control large collector current ,   When used as an amplification element , The triode needs a certain input current ,   Therefore, it is called current control current element .

Field effect triode uses a certain input voltage to control a large output current ,   When used as an amplification element , The field effect triode only needs a certain input voltage , There is no need to input current ,   Therefore, it is called voltage controlled current element .

Field effect triode has high input resistance 、 Low noise 、 Good thermal stability 、 Strong radiation resistance and other characteristics , And less energy consumption 、 The production process is simple 、 Suitable for integration and other advantages , It has been widely used .

Performance comparison between FET and crystal triode

（1） FET is a device that voltage controls current , Its input impedance (>10 Of 7 Power Ω ), Crystal triode is a device for current control ,  Its input impedance is small ,  However, a larger voltage amplification factor can be obtained .

（2） The operating voltage range of FET is wide , Good thermal stability ; The operating voltage range of the crystal triode is small , Poor thermal stability .

（3） The manufacturing process of FET is simple , The price is cheap , It is widely used in manufacturing large-scale integrated circuits .

（4） When FET is not in use , All levels should be short circuited , Prevent external electrostatic induction from generating high voltage and damaging it .