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

[Andrew Dixon]

I think your problem is with pin 5.  According to the datasheet, pin 5
should be *half* Vs, which is 4.5 volts in your example.  You could get 4.5V
by hooking up a voltage divider, eg a 10k resistor from pin 5 to your
battery +ve and another 10k resistor from pin 5 to your battery -ve.  This
will give 4.5V at pin 5.

Hope this helps you out!

Andy



>
> > 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