next up previous contents
Next: Multiple Transistor Circuits Up: Transistor Circuits Previous: The Insulated-Gate Field Effect

Power MOSFET Circuits

Traditionally, MOSFET devices have had the drain-to-source current confined to a thin planar volume of silicon lying parallel to the gate. The limited cross-sectional area of material thus available for conduction effectively limits the power-handling capability of MOSFET devices to less than 1 W. More recently, new designs and manufacturing techniques have been developed to produce a more complicated, three-dimensional gate structure. These transistors are identified by various manufactures as HEXFET, VMOS, or DMOS, depending on the geometry of the gate structure: respectively hexagonal, V-shaped, or D-shaped. They feature power dissipations exceeding 100 W and excellent high-frequency operation. In contrast to the normal MOSFET, these devices have a much larger forward transconductance. These devices thus feature very high current gain at both high frequency and high power, a combination that is hard to obtain with traditional bipolar power transistors.

Doug Gingrich
Tue Jul 13 16:55:15 EDT 1999