2n6660.pdf datasheet:

Supertex inc. 2N6660N-Channel Enhancement-ModeVertical DMOS FETFeaturesGeneral DescriptionThe Supertex 2N6660 is an enhancement-mode (normally- Free from secondary breakdownoff) transistor that utilizes a vertical DMOS structure and Low power drive requirementSupertexs well-proven silicon-gate manufacturing process. Ease of parallelingThis combination produces a device with the power handling Low CISS and fast switching speedscapabilities of bipolar transistors, and the high input Excellent thermal stabilityimpedance and positive temperature coefficient inherent Integral source-drain diodein MOS devices. Characteristic of all MOS structures, this High input impedance and high gaindevice is free from thermal runaway and thermally-induced Hi-Rel processing availablesecondary breakdown. ApplicationsSupertex