Quadrature VCO schematic posted

[Magnus Danielson]

From: Chris MacDonald <macdonald at evenfall.com>
Subject: Quadrature VCO schematic posted
Date: Mon, 09 Oct 2000 01:01:02 -0700

> Thanks to some help from list members, I have put together a quadrature
> sinewave VCO.  The circuit is based around the Mini Modular 12 dB
> state-variable filter, with zener regulated positive feedback for
> oscillation.  I believe that Harald Bode came up with the original
> circuit concept.  Please correct me if I am wrong on that.  If anyone is
> interested, there is a pdf of the schematic available on my DIY site:
> http://www.evenfall.com/diy/index.html

Ah, nice. But being a bit picky, this is just an quadrature
oscillator core, but I don't see any CV input. I personally see
exactly what treatment which would be appropriate to have a CV input,
but for other less oriented in the field would be confused by having
this called an "VCO".

In essence this is just an state-variable filter brougth up to self
oscillation and the diode setup ensures the stabilization of the
amplitude. If you compare this to the SEM/ASM-1 filter you are close.

Cheers,
Magnus