Power BJT - Necessity of vertical structure

Q. What is/ are the necessity /ies of using a vertical structure in Power BJTs?
- Published on 23 Sep 15

a. Increase in cross-sectional area to allow the flow of device current

b. Reduction in on-state power dissipation of transistor

c. Reduction in thermal resistance to keep the problem of power dissipation under control

d. All of the above

ANSWER: All of the above

Satyawati -Posted on 05 Oct 15
A power transistor consists of vertically oriented four-layer structure of alternate p-type & n-type layers. Its doping level resembles to that of n-p-n transistor.

Use of vertical structure in power transistor results in increasing the cross-sectional area of device. Thus, the area for the flow of device current also increases in power BJT. As on state resistance of device is reduced, it also helps in minimizing the on state power dissipation in the transistor.

The resistance offered to the flow of heat in a transistor is regarded as 'Thermal resistance'. Therefore, the thermal resistance of transistor is reduced to greater extent. However, the overall problem of power dissipation can be controlled due to vertical structure of power BJT.

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