[sdiy] harmonic generator

[Magnus Danielson]

From: media.nai at rcn.com
Subject: Re: [sdiy] harmonic generator
Date: Sun, 24 Feb 2002 18:17:15 -0500

> At 8:16 PM +0100 02/21/02, Magnus Danielson wrote:
> >
> >You could make a good tracking PLL if you want to, but one has to use
> >higher degree PLLs to get a good result, which usually is out of scope
> >for most people.
> 
> Perhaps its out of my scope as well!!  I have thought about using a
> discrete PLL using flip-flops for a phase detector and a
> voltage-to-frequency converter chip, but V/F chips are expensive, and the
> resulting parts count would be enormous.  I'm not sure what you mean by
> "higher degree".  Considering all the various PLL chips available, which
> would you recommend??

To do a higher degree PLL it is less an issue of which chip one used
but rather how many poles the loop filter have. If you want a 3-pole
PLL then since you intrinsically have a pole in the oscillator you
need to have a 2-pole filter.

You can use many forms of phase detectors, such as those in the 4046,
'HC7049 and 'HC9046. As for VCOs you can build yourself one around
basically any oscillator core. You don't need the expo's, you only can
feed the driving current from an buffering op-amp and through a
resistor.

But the 4046 and friens are not good oscillators if you aim for
sine-waves.

Cheers,
Magnus