The integrated VCO question

smusic at smusic at
Sun Aug 6 17:43:13 CEST 1995

Hi all. I'm new to this list and joined because I'd like to build a modular.

I have built / modified a Fatman and I'm ready for the next step. I have been 
busy getting catalogs from supply houses, looking for a cheap used o-scope, 
etc, etc...   -soon I hope to start doing some serious building (at the 
expense of actually spending time MAKING music!!!)
Anyway, I'm still no expert on the technical aspects of electronics, but I'm 
learning as fast as I can. I read the digests of this list and there was a 
question a while ago about integrated VCO chips and some long discussions on 
VCO's in general.

Well, while poking around on the net I found the following in the Harris Data 
sheets for  Harris Semiconductors;

The ICL8038 Waveform Generator
   "The ICL8038 waveform generator is a monolithic
    integrated circuit capable of producing high 
    accuracy sine, square, triangle, sawtooth and pulse 
    waveforms with a minimum of external components. The 
    frequecy can be selected externally from from .001 Hz 
    to more than 300kHz using either resistors or capacitors, 
    and frequncy modulation and sweeping can be 
    accomplished with an external voltage.
    Tempurature drift = 250ppm/'C. From -55 to 125 'C"

-It almost seems too easy. Is it? is this too much drift for synth VCO 
applications? The data sheet mentions using it as part of a "phase-locked 
loop" to get the drift below 250ppm. How does this work?

If this sounds like a useful VCO chip, someone who can really understand these 
data sheets should look into it.

Any thoughts?


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