Re: Dual sine wave generator with variable frequency and 90 degree phase difference

On Sep 3, 9:42 pm, Steve <st...@xxxxxxxxxx> wrote:
I'm looking for a waveform generator that outputs two sine waves of
the same frequency with 90 degree phase difference (sine and cosine).
I need a variable frequency between 0.05 Hz and 10 Hz. Is there an
analog design that uses a single potentiometer or perhaps is voltage
controlled ? Low distortion is not a requirement.

Steve

With only a little trickiness, you can get two variable gains from one
pot. You ground the wiper and use the two ends as variable
resistances.

Th classic 3 op-amp "state variable" oscillator naturally makes two
outputs at 90 degrees. The tricky bit is making their amplitudes
equal. For this you need two equal variable gains. I think I have
seen a circuit that does this but I can't remember it right now.


.

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