Re(1): V/Oct >> Hz/V converter circuit?

[Magnus Danielson]

From: "jhaible" <jhaible at debitel.net>
Subject: Re(1): V/Oct >> Hz/V converter circuit?
Date: Sat, 15 Jan 2000 19:04:57 +0100

> 
> > I believe that all analogue VCO designs have at their heart, a
> > linear (v/hz) VCO.  V/oct VCOs have what is called an exponential
> > converter or expo converter that translates the incoming v/oct
> > control voltage to linear (v/hz) which then controls the oscillator.
> 
> No. It's a widespread misconception.
> The core of almost every VCO is a CCO (current controlled oscillator),
> which is inherently linear ("amperes / Hz").

Actually, we need to compensate for the reset time of the capacitor in order
to make then linear. However, when this is then done we are pretty linear.
We could then invent more forms of error terms, but I think the reset time is
the main error and the accuracy by which it is being corrected.

> A V/Oct VCO has an exponential voltage -> current converter in front of
> this core.
> A V/Hz VCO has a linear voltage -> current converter in front of this core.

Interesingly, I have allways been annoyed about the lack of standard on these
expressions. In one end it is V/oct where as the other is Hz/V. Both are
being voltages but they are given unit-names which is built a diffrent fasion.

The V/Oct as in 1 V/Oct gives the conversion factor of how to convert from
an octave unit into volts. The Hz/V gives the conversion factor from volt to
Hertz. I think this is a bit illogical and inconsistent. However, it seems to
be some historically accepted terms so...

Cheers,
Magnus