[sdiy] the most simple semicon VCO ever built

[R. Drake]

dunno if this is the same thing, or kind of thing, but here's a circuit
diagramed in the terence thomas book, identified as a negisistor oscillator:

                                     c1
                                -----|(-----
                               |            |
+        r1            r2      |            |
o----/\/\/\/\/\----/\/\/\/\/\-----        ---------
                 |      ^      |   ^     /         |
                 |      |      |    \   /         ---
                  ------       |    -----          - grnd
                               |      |
                               |      NC
                               |
                               |
                                -----|(----o out
                                    c2
r1: 1k
r2: 10k
c1: 1uf
c2: 5uf
q1: 2n2222

he claims that it's "stable and linear", but has a limited frequency range.
i probably could have breadboarded it faster than draw it out in ascii
(expecially with my cat walking on the keyboard as she is), but i haven`t
tried it, so i cant tell you if/how it works...

lbd                


From: "Czech Martin" <Martin.Czech at Micronas.com>
Subject: [sdiy] the most simple semicon VCO ever built
Date: Tue, 25 Mar 2003 13:53:26 +0100

> Yesterday I browsed through a 1970 something issue of the
> "Funkschau" mag. I saw a simple VCO, one cap , one
> npn one resistor. Obviously the transistor was working
> in tunnel diode breakdown, thus creating negative
> impedance characteristic.
> 
> The base was left open, but it was said that it could be used
> for frequency control.
> 
> If there is some interest, I could scan this little
> picture. Perhaps one more item to the "most simple modules
> collection" a la Korg.