high freq vco

[René Schmitz]

Hi all,

I'd prefer a bipolar IC instead of a CMOS one for a VCO. The MOS current
mirrors are different from the bipolars in that they must be operated with
equal Vds on both legs of the mirror for unity mirror gain. I'd mistrust
the 4046s linearity. I'd like to throw the LM566 into the debate here, it
works nice over about 8 octaves when controlled by a current source. 
Also I've operated sawtooth based VCOs (CMOS schmitt trigger with 220p cap
to GND at input, and diode from out to in) at up to 3MHz. The linearity
isn't ideal, but comparable to that when operating such a thing at audio
frequencies, since the reset time scales along with the cap (neglecting
switching times). HF-compensation should come to the rescue.

Bye,
 René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159