Patent ID: 7042293
Filing Date: 2006-05-09
Classification: H01L,H02M

Abstract:
1. A DC/DC converter comprising: an input terminal receiving a DC power input; an output terminal; a grounded terminal; a smoothing capacitor connected between said output and grounded terminals; and a bipolar transistor having a base, an emitter and a collector, said bipolar transistor being operable to turn on and off at high speed so as to switch said DC power input received through said input terminal and generate an output DC voltage on said output terminal, wherein said base of said bipolar transistor includes a first silicon germanium layer and a second silicon germanium layer, said second silicon germanium layer being in contact with said emitter of said bipolar transistor, said first silicon germanium layer has a germanium concentration of 6 to 16%, said second silicon germanium layer has a germanium concentration less than that of said first silicon germanium layer, said base has a total thickness of 60 to 90 nm, said collector has a dopant concentration of 5×10 said bipolar transistor has a rated collector-emitter breakdown voltage of at most 50V, said bipolar transistor has a current gain of 300 to 500 at on-time with a collector-emitter voltage of 0.1V, said DC/DC converter has a switching frequency of several tens of MHz, and said bipolar transistor has a turn-on time and a turn-off time of at most 0.5 nsec.