Design of the Collector Layer

The blocking voltage of a power BJT is supported by the collector layer. In Si power BJTs, it is known that a very low specific on-resistance can be achieved due to the conductivity modulation in the lightly doped collector epilayer. However, none of 

The specific on-resistance of the collector layer is simply given by, 

The blocking capability of a power BJT is generally determined by the open-base breakdown voltage (BVceo) of the device. The S usually much smaller 

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