[sdiy] RE: [AH] A question about voltage controlled oscillators.

[patchell]

    LOL.....boy, did  somebody blow it on that data sheet.  That circuit will
never work!  I am not surprised.  That is not the only one that is wrong.  The
Low Pass filter, Fig 23 has the inputs of the opamp swapped.

    Believe it or not, this is very similar to the first VCO I did which you
will find in the LM324 Data sheet from national semiconductor.  If you look at
that circuit, you will see why the one down below will not work.

    If you don't have a national linear book, or can't find the data sheet on
the national web site, let me know, and I will scan the circuit and send it to
you.

    Try this url: http://www.national.com/pf/LM/LM324.html#Datasheet

    Good luck.

Alex Dickey wrote:

> > Is it possible to build very simple (one or two opamps, a few
> > resistors,
> > a few capacitors, diode, transistor...) VCOs that will output up to
> > audible frequency, or... not?
>
> check this datasheet out:
> http://www.fairchildsemi.com/ds/RC/RC4558.pdf
> (oscillator's on page 8)
>
> but i'm having problems getting this to work.  i think part of it is that
> i'm probably mixing up my Vs' and Vc's.  can anybody shed some light here?
> i was powering this using a 9v on a clip, and i had + from the battery going
> to both pin 8 and pin 5, - from the battery going to pin 4, and then Vc and
> the outputs going to jacks, with the jack grounds tied together.
>
> can anyone see where i went wrong?
>
> thanks,
> alex

--
 -Jim
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