[sdiy] Simple VCO design

[Aaron Bader]

Hello all:

I thought'd I post a VCO that I just designed and tested a day or two
ago; the main goal was low parts count:

http://sparked.zadzmo.org/simple-vco.png

The prototype is almost exactly as shown, with a 10K pot being used as
the control voltage source. The transitors in the current mirror were
matched using the hfe test on my DMM. With the mirror powered by +12
volts it swept from 160 hertz or so to over 380 kilohertz, with an
almost perfect sawtooth wave the entire way. 

I'm not sure how linear it is as I don't have a good way to output
exact test voltages, though I would expect it to be at least respectable
if the mirror is well built.

-- 

"Not a bird not a leaf not a sound/And well after the close of time" 
	--Front 242

Public Key: http://sparked.zadzmo.org/

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