dumbass semiconductor question

[media at mail1.nai.net]

I asked:

>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??

At 11:20 AM +0000 06/11/98, Scott Gravenhorst wrote:
>
>If the NPN transistor is used as a common emitter switch, then 2
>transistors could be used.  The first one inverts for the second one.
>

I think these pills for my back are making me stupid.  So how are these
hooked up together??   The collector of the first NPN is connected to the
base of the second??

At 3:57 AM -0500 06/11/98, tomg wrote:
>
>Try a 4066 instead of a transistor.
>
>
>          +V
>
>          ^
>          |
>          /    +------
>     100K \    |
>          /    |
>          \  +-+-+
>          |  |   |
>          +--+   |
>          |  |   | 4066/16
>        \    +-+-+
>         \     |
>          |    |
>          |    +------
>         -+-
>          -
>
>
>Close the switch the 4066 opens. Open and the 4066 is closed.

Thank you for taking the time to draw the diagram.  What's a 4066??
However, it seems like it acts just like an NPN transistor (it conducts
with when a current is applied to the base).  Pictured above, the 4066 is
closed when current is flowing through it's center pin and open when it is
dropped to ground.  Is that what you meant??

I guess I could use an NPN to replace the mechanical switch in the above
diagram.

What I am looking for is a simple three-legged animal that is a normally
closed switch, that opens when it receives a voltage.  I guess I'm just
surprised that they don't make such a thing.

At 9:01 AM -0500 06/11/98, Tim Godfrey wrote:
>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.

I'm still confused.  So no voltage the switch is closed, with a little
voltage the switch opens, but it closes again if it reaches the voltage
being switched??

THANX!!

PEACE OUT :)
MARK