Power switching transistors - A prognosis

For switching regulator and other related applications, high-voltage bipolar transistors have long been a mainstay of the power semiconductor device industry. Recently, this position has been challenged by the development of power MOSFETs which have voltage and current control capabilities that compare favorably with the bipolar. In this paper, both devices are discussed. As one might expect, various properties of the lightly-doped collector (drain) region are crucial to the design of both transistors. The theoretical steady-state or conduction loss of both devices is compared on a per unit area basis. It is shown that the bipolar will usually have a smaller voltage drop. Thus to enjoy the advantage of the lower switching losses of the MOSFET, it is necessary to operate at a sufficiently high frequency.