[?] Audio VCO design

[Rich Grise]

On Fri, 20 Nov 2009 14:14:56 -0800, whit3rd wrote:

On Nov 20, 1:39 am, David Chapman <d...@minda.co.uk> wrote:
   As part of a larger system, I need to design and build an audio VCO
which will produce tones ranging from around 50Hz to 4KHz or so when the
applied DC input voltage changes from 0.5volts to 2.5volts.

   I'm considering using the CMOS 4046 PLL IC,

The thresholds in a '4046 (CMOS) are variable unit-to-unit, some better
precision can be had with a linear design; I'm thinking of XR2206, LM331,
and similar chips. The basic scheme is to use the voltage input to
program tracking current source + sink elements, onto an
integrator-connected amplifier into a comparator with suitable hysteresis.

In other words, a 555. ;-)

Analog switches, diode switches, current mirrors, or transconductance
amplifiers are the key components.

Cheers!
Rich