dumbass semiconductor question

[Tim Godfrey]

At 01:12 AM 6/11/98 -0400, media at mail1.nai.net wrote:
>So what kind of gizmo can I use to the switch that will normally be closed
>(not running) and open (run) when it receives a voltage or from a keyboard
>gate or x0xbox sync??
>


Mark,

A depletion mode JFET will do what you want. The channel is normally
conductive. For an N-channel JFET you drive the gate to a negative voltage
with respect to the source (greater than the "pinchoff" voltage) and the
Drain - Source connection no longer conducts. For a P-channel JFET, the
gate goes positive with respect to the drain to turn off the channel.

Discrete FETs are getting rare these days. Check the surplus catalogs,
though. I can't remember any particular numbers right now, and I'm away
from my databooks.

Tim.

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