[sdiy] LM13700 Oscillator Circuits and analog computers

[Scott Gravenhorst]

Ian Smith <taciturn_unquiet at hotmail.com> wrote:
>
>Hello all,
>
>I was advised to look at the application notes for the LM13700 
>and I have a few questions. On the Triangular/Square-Wave VCO, 
>would replacing Ra with a potentiometer allow the changing of the 
>frequency ? 

I can help here: I built a _linear_ version of this oscillator, but the principle is the same for
expo.  You would replace Ra with a current source, for expo, use an expo current source, for
linear, use a linear current source.  Mine works very nicely in my FatMan which is why mine is linear.

Here is the schematic: http://home1.gte.net/res0658s/fatman/vcngvco.html (it's actually an LM13600
in mine).  The top portion is the linear current source feeding pin 1 of the LM13600.

Someone else here likely already has an expo version of this that you can build.

..

-- ScottG

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-- Scott Gravenhorst
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