[sdiy] 4069 VCO again

[Scott Gravenhorst]

jbv <jbv.silences at club-internet.fr> wrote:
>Hi,
>
>I have a couple more questions about the 4069 VCO
>described here :
>http://www.uni-bonn.de/~uzs159/vco4069.html
>
>- I didn't found anything about stability & calibration...
>any clue ?
>
>- I was wondering how this little thing would behave
>in a polyphonic context (several such VCOs in parallel)...
>any risk to see them lock together ? decoupling issues ?
>
>- how to modify it to accept 1V/oct VC from a uC + DAC
>+ SH expo converter ? I guess it'll make the circuit even
>simpler...


This VCO uses a current sink.  You need to design your
digital controlled system to provide programmable sink to
ground.  I converted this VCO to linear (vice expo) by
creating a linear current sink instead of an expo one and
connecting it where T2's collector is connected.

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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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