Importance

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Abstract

In a bipolar transistor, a thin gate oxide, preferably less than 600 Å, is formed over the base surface region between the emitter and collector. A conductive gate, such as doped polysilicon, is then formed over the gate oxide and biased at the emitter voltage. In the example of a PNP transistor, when the emitter is forward biased with respect to the base to turn the transistor on, the gate is at a positive potential relative to the base. This causes the holes in the base conducting the emitter-collector current to be repelled away from the surface, and the electrons in the base to be attracted to the surface, so that more of the emitter-collector current flows deeper into the base. Thus, the effect of defects at the base surface is mitigated, and 1/f noise is reduced. The invention is equally applicable to PNP and NPN transistors. Other benefits result.

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First Claim