4046 VCO experiment

[Scott Gravenhorst]

Martin Czech <czech at Micronas.Com> wrote:
>The current source should be pretty linear but with some error at the
>low end. (Why not use a jfet precision current source?).

I could, if I knew how to put that together.  Is there a reference
in the Art of Electronics that would help me?  (sorry, but my
design chops get pretty lame, I'm really a coder, never an EE).

>I think the inner VCO circuitry is not published.  Linearity is not
>neccessary for most of the applications.  Who will demodulate FM with that
>chip anyway?  It seems to be fabricated in the very same CMOS process
>then anything else of this logic family.  So there are limitations on
>matching, mirrors etc. Certainly the internal integrator has low gain
>(but high bandwidth).

What's this for anyway, decoding FSK?

>Could you be more specific on the error?

I could try to make some measurements, but they'd be using
only an oscope (no freq counter) and an old fluke DVM.  When
I say that it isn't linear, I mean that the output freq more
(alot more) than doubles for a doubling in CV.

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