_[sdiy]_ICL8038 worst ic off all time!

[Karl Dalen]

Scott,f,jg...fio....,,n>>
> >Hmm, i dont think the VCO sucks,as i remember, BJ showed once many
> years
> >ago that you could build a remakable advanced VCO out of a 4046 IC!
> Well,
> >at least a "very high frequency LFO" with sync and 4 quadrant
> modulation
> >on the square, if im not remebering completely wrong, thats not bad for
> >such a cheap and simple IC. Or one could use the HC version and do a
> >nice DC to 30Mhz function generator. I say forget about the 8038! 
> 
> Looking at the spec, a 4046 is rated at 1.3 MHz, the 74HC4046 version
> runs
> at max 17 MHz.  The VCO is fine, it's the current source that isn't very
> good.  Check the TI docs, it has a whole section on the technicals of
> the VCO.

I have managed to squeese up a HC4046 to just abowe 30Mhz, 
i sat down a evening a selected among some manufacturer lots,
its a horrible design all in a closed ohven since i only use 
it as a function generator! Most of the HC i tried out did 20-24Mhz.
 
> I built up that circuit by Bjorn Nilsson(?) and couldn't
> get it to track a linear CV.

As far as i can remeber the thing when it was discussed
he did mentioning someting about the tracking and some 
sugestions to solve that, i think he said something about
it could be used up to a 1,5 2khz range with fairly good
tracking, bass range i cloudly remember.

Hmm, i recall that Grant Richter did use the saw
tooth trick BJ mentioned in one of his modules?!
Darn clever thing to pull out a sawtooth out
of the 4046 anyway!! I think it was something about 
dissconecting one end of the charge cap and connect
that end to gnd or +5V!? 

KD

> >Speaking of function generators, you can use a PNP expo on the I set 
> >pin on the MAX038 to convert it to a expensive VCO!
> >
> >KD
> >
> >
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> >
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