[sdiy] Sine VCO

[Magnus Danielson]

From: Tim Ressel <madhun2001 at yahoo.com>
Subject: Re: [sdiy] Sine VCO
Date: Fri, 28 Mar 2003 09:08:14 -0800 (PST)

> Hi,

Hi Tim,

> The way I would do this is to make up a sine
> oscillator using 2 integrators in a loop, and put a
> pair of OTAs in to control the integration rate. This
> would be akin to making a state-variable filter
> oscillate. There is a schematic in Jung's Opamp
> Cookbook in the oscillator section for basic sine
> oscillator.

There is plenty of schematics in OTA datasheets for this solution.
It is not uncommon to see this solution being able to handle 6 decades
(20 octaves) of frequency range. The benefit is that you get quadrature output.

The trick here is to ensure that the AGC is pretty good, or it will perform
non-linear modulation causing distorsion. I've seen that in action and it's
not pretty.

Cheers,
Magnus