his is a schematic representation of a VN300M
Positive Channel Enhanced Mode VMOS Power FET. This type of device is as close to
the perfect switch as you can get. This transistor works very much like the
electron tubes of days gone bye, except of course, that it is solid state. Like
the old electron tubes, it uses a small voltage to control a large current. Most
of the usual transistors are bipolar devices in which a small current controls a
larger current. There are other specialty transistors such as Unijunction
Transistors, and Hall Effect Transistors as well.
One of the most useful uses for a VMOS Power FET
is as a high current, fast acting saturated switch. It does for DC circuits what
the Triac does for AC circuits, and can be found in switching power supplies,
proportional motor and/or temperature controllers. When this device first became
available in the 1970s I used it in a portable Ski Timer to control the current pulses through
a heating element in a miniature oven, to keep the timer's crystal controlled
oscillator at a constant temperature. Here I will use a pair of them to control
each telescope motor.
