I'm trying to make a device that will (through a speaker) produce a tone modulating between 20kHz and 30 kHz. I know that this is out of the hearing range of most people, but thats ok.
My plan was to have a ramp generator that would power a VCO. At the lowest voltage the VCO would produce 20kHz and at the highest is would produce 20 kHz. I would then run the ouput of the VCO through an amplifier circuit.
The problem is that I can't find a VCO that will opperate in the coorect range. All that I find opperate in the 1MHz+ range.
I've thought about just using a two crystals and running them through a summing amplifier, but I dont think it will produce simlar results (I know there would be no modulation).
Any I ideas or timps on parts would be helpful. Are there any PLLs out there that opperate this low?
My plan was to have a ramp generator that would power a VCO. At the lowest voltage the VCO would produce 20kHz and at the highest is would produce 20 kHz. I would then run the ouput of the VCO through an amplifier circuit.
The problem is that I can't find a VCO that will opperate in the coorect range. All that I find opperate in the 1MHz+ range.
I've thought about just using a two crystals and running them through a summing amplifier, but I dont think it will produce simlar results (I know there would be no modulation).
Any I ideas or timps on parts would be helpful. Are there any PLLs out there that opperate this low?