[sdiy] Imperfect VCO

[Magnus Danielson]

From: Grant Richter <grichter at asapnet.net>
Subject: Re: [sdiy] Imperfect VCO
Date: Wed, 30 Jul 2003 14:32:13 -0500

> Franco HF compensation (R in series with timing cap) distorts the waveform
> as frequency increases. Using a very poor exp. pair (like PNPs in CA3096)
> requires Franco compensation in the order of 10K with extreme waveform
> shifts. Built some "unintentionally".

It's not the expo-pairs fault you fix with Franco HF compensation - unless you
want to do it the wrong way... no, the Franco HF compensation is there for the
time it takes to empty the poor little capacitor, nothing else. Poorly trimmed
reset-timing or a large one needed for a too bad reset-transistor causes the
Franco compensation to cause larger distorsion.

The expo-setup you correct over there... and you can get pretty darn good for
most uses without too much fiddeling. Then there is always room for
perfections.

However, if you want to crush things, just take all advice the opposite way ;O)

Cheers,
Magnus