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Reverse voltage controlled oscillator?

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Firnagzen

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Is there such a thing as an oscillator that, the lower the voltage supply, the higher the oscillation frequency? All the VCOs I see are that both decrease together.
 
Firnagzen said:
Is there such a thing as an oscillator that, the lower the voltage supply, the higher the oscillation frequency? All the VCOs I see are that both decrease together.
Sure. If you have an existing VCO design, all you have to do is invert and offset (level shift) the control voltage. Do you need such a circuit? if so, what do you need it to do?
 
After level shifting and/or inverting, you can have the level on the input of the op amp (the inverter/level shifter) such that with zero volts, the oscillator will be at its design center frequency value. With a positive voltage, the frequency will go above that center frequency and with a negative voltage, the frequency will go below that center frequency. With inversion on the VCF input, a positive will drive the frequency down from center and a negative up from center.

A simple op amp circuit will perform inversion, level shifting and gain modification (i.e., VCF input voltage-to-output frequency ratio) all at once.

Dean
 
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