dumbass semiconductor question

[tomg]

>Thank you for taking the time to draw the diagram.  What's a 4066??

A CD4066 is a CMOS quad bilateral switch. The 4066 is a better choice because
you can switch anything just as if you had a SPST connected instead of an ic.
Switching voltage is fine as long as the voltage does not go above +V or below
gnd. If you need to switch a negative voltage it can be run on a +- 7.5V split
supply but no more. You can even connect the control pin to inverters or
buffers for logic/CV switching.

>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.

They did...they just put 4 of them in one package it's called a CD4066. I
guess you want to use a transistor.

  


                 +V
                 ^
                 |
                 /
                 \ 10K
                 /
                 \
     100K        |----o   
               |/
 i__/\/\/\-----+
               |\  2N3904
                 V
                 |
                -+-
                 -

The output is normally high if the input is low. If the input is high the
transistor turns on and the output goes low.
      
-Tom