Stock Code:800328

Is The MOSFET A Triode?


Is The MOSFET A Triode?

Is the MOSFET a triode? In layman's terms, the triode is a current control element, and the field effect tube is a voltage control element. Both are semiconductor devices, but the working conditions are different. Field effect transistor is a special semiconductor device, which has the advantages of most transistors, such as high input resistance, low noise and good thermal stability.

main feature

1. High input resistance

2. Large current amplification factor

3. Good thermal stability

A field effect transistor consists of two parts, p-type and n-type. When a forward voltage is applied to the pn junction, since the holes in the p region are injected from the n region into the pn junction electric field to form a space charge layer, these space charges combine with the electrons drifting to the pn region to prevent the diffusion movement; at the same time Due to the existence of the inverter, the diffusion movement of electrons is also prevented. Therefore, the entire pn junction presents two regions, a space occupied by positive charges and a space occupied by holes. When the applied reverse voltage reaches a certain threshold, the reverse bias voltage will make the boundaries of these two regions disappear and make the two regions overlap each other to form a depletion region, that is, a cut-off state or a saturation state. At this time, if the forward bias voltage continues to be applied, the depletion region will be widened and its internal resistance will increase, which will eventually lead to breakdown and damage of the tube; on the contrary, if the reverse bias voltage is reduced, a new one will appear in the cut-off region. Hole-electron pairs and produce a small self-excited oscillation phenomenon to make the tube conduct until the tube burns out. Since there are two main failure modes of the field effect tube in the normal state:

(1) short circuit

(2) open circuit

(3) breakdown

Among them, the first two cases are irreparable faults, and the latter two cases are repairable faults. Both open circuit and short circuit are permanent damage, so generally we will not consider the maintenance problems of these two cases. The breakdown of field effect tubes belongs to one. This kind of temporary damage can solve the problem as long as a new chip is replaced.

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