[sdiy] the most simple semicon VCO ever built

[Czech Martin]

nice to hear that.
So far I did only tamper with sub micron CMOS npn snapback.
So I knew it was there, but I did not know if it would work
with discrete stuff.

Juergen, this is certainly a candidate for the most simple
synth circuit. A good analogon for the tube area lamp
oscillators.

m.c.

-----Original Message-----
From: IXQY at aol.com [mailto:IXQY at aol.com]
Sent: Freitag, 28. März 2003 16:31
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] the most simple semicon VCO ever built



 Hi all,
 I tried a rough version of the circuit below (built it on a IC DIP socket 
:). I had limited parts available where I was, so I wound up using a single 
5.8K resistor for R1 and R2. For C2, I only had a 330 uf or something like 
that (this value took a a second to get rid of the DC offset). The other 
parts were of the correct values.

 Anyway, I hooked a scope up to the output, and found a rising sawtooth wave! 
I was surprised that it worked due to my limited setup. I didn't hook up the 
base of the transistor, but instead varied the voltage supply. At a low 
voltage of 7.5V, the frequency went down to about 70Hz with a slight rounding 
of the waveform. Below 7.5V, the oscillator didn't work. I went as high as 
20V on the power supply, which yielded around 1KHz (i think it was).  ...and 
then I had to go back to work. :)

  Cheers,
  Andrew Sanchez


In a message dated 3/26/03 6:09:49 AM Central Standard Time, 
Martin.Czech at Micronas.com writes:

> 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