[sdiy] CMOS VCOs

[Ryan Williams]

hi all,

I'm needing a VCO to clock a 4015 shift register for a digital noise 
source. I have two extra xor gates from a 4030BE that I was trying to 
use to make a VCO similar to René Schmitz' 4069 VCO. Actually I have 
this working but the output is kind of strange. The power supply is 15V 
so I expected a 0,+15 pulse output from the schmitt trigger. Instead I'm 
seeing about a 0,9V pulse. The 4030 is quite cool when the circuit is 
running. but I thought it might have something to do with drawing too 
much current from gate's output when the integrator's reset diode is 
turned on?

I could just use a 4046 PLL's vco and I have that on the breadboard 
also, but I wanted to try some other things and also get exponential 
response on the oscillator.

anyone know of anything to read about doing this type of thing with cmos 
gates?

thanks---Ryan