[sdiy] Re: RE simple vco

[sbernardi at attbi.com]

I'm having some problems uploading the schematic I referenced for the simple 
VCO. I was answering this at lunch time from woek, looks like I'll have to do 
the upload when I get home. Stay tuned...
> Depends on what your definition of "simple" is, and how much performance
> you're willing to trade for low parts count. The circuit below will give you
> a good quality wide range 1 v/octave VCO that will track a keyboard.
> http://home.attbi.com/~sbernardi/elec/og2/simple_vco.gif
> <http://home.attbi.com/~sbernardi/elec/og2/simple_vco.gif> .
>  
> Some notes:
> Q1 and Q2 need to be matched for Vbe, and glued together. RTC1 should be a
> tempco resistor, also glued to the pnp's. You can go without the tempco
> resistor but you'll get some frequency drift with temperature. U3 can be a
> 748 or uA301 uncompensated opamp.
> If you don't care as much about tracking, you can get simpler by user a less
> accurate exponential generator. See 
> http://home.attbi.com/~sbernardi/elec/og2/og2_lfo.gif
> <http://home.attbi.com/~sbernardi/elec/og2/og2_lfo.gif>  and the circuitry
> built around U1, Q1 and Q2.
>  
> Scott Bernardi
> ICT/ Acquisition Technology
>  
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