Difference between asemi high power FET and triode

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Field effect transistor is also called field effect transistor , abbreviation FET, High power FET is a kind of semiconductor amplifier . The FET not only has a small transistor size 、 Save electricity 、 Durability and other advantages . High input impedance 、 Low noise 、 Good thermal stability 、 Low power consumption 、 Large dynamic range 、 Advantages such as wide safe working area . Here is ASEMI Difference between high power FET and triode .

 

Comparison between high power FET and triode

The polarity of the applied voltage of the high-power FET is the same as that of the common triode we use . N The channel is similar to NPN T-triode . Drain electrode D Connect the positive pole , Source pole S Connect the negative electrode , Grid G Connect positive voltage . When the conductive channel is established ,N The channel fet turns on and starts working .

Again P The channel is similar to PNP triode , Drain electrode D Connected to negative electrode , Source pole S Connected to positive electrode , Grid G When the voltage is negative, the conductive channel is established and starts to work .

Compared with high-power triode , High power FET has high input impedance and low driving power . The DC resistance between the grid and the source is basically large ,100 Megaohm or so , The AC input impedance is basically the capacitive reactance of the input capacitance . Due to the high input impedance , It can be driven by voltage , So the input power is very small . Common triode must have base voltage and base current to drive the generation of collector current .

The switching speed of high power FET is closely related to the characteristics of input capacitance . Due to the existence of input capacitance characteristics , The switching speed becomes slower , But when used as a switch , It can reduce the internal resistance of the driving circuit , Speed up the switch （ The current increases , Speed up capacitor charging and discharging ） FET only depends on the conduction of many sub carriers , There is no minority carrier storage effect , So the shutdown process is very fast . Triode due to minority carrier storage effect , Make the switch always lag , This will affect the switching speed .

After the high-power FET is turned on , The characteristic is pure resistance . The common triode is almost straight through when it is saturated , There is a very low pressure drop , It is called saturation pressure drop . After opening , Equivalent to a very small resistance , But this equivalent resistance is a nonlinear resistance （ The voltage across the resistor and the current flowing through it do not conform to Ohm's law ）, And the FET also has a very small resistance after saturation conduction , But this resistance is equivalent to a linear resistance （ The value of the resistance , The voltage drop across the resistor and the current flowing through it conform to Ohm's law , Large current and voltage drop , Small current and voltage drop ）.