digitally controlled oscillator dco design


Posted on Feb 7, 2014

I am trying to design a digitally controlled analogue oscillator. The idea is that a control voltage is generated by the a microcontroller (Arduino) which is used via the 2 op amps, resistor and capacitor network which forms a integrator circuit. The microcontroller will also send out a squarewave (top left) at the desired frequency which gets con


digitally controlled oscillator dco design
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verted eventually via the transistor and shorts the ramp voltage to ground. This forms the sawtooth circuit. That`s technically not an oscillator, it`s a sawtooth generator. An oscillator is autonomous (no external input), and free-runs by virtue of positive feedback. You don`t need the 1Meg resistor. It just makes your ramp slightly nonlinear. You will have to adjust your values slightly if you want to omit it and still get exactly 9. 5V peak. Yes, it`s not a true oscillator. I`m trying to design a digital oscillator for a music synthesizer. The outputs will eventually be ramp (sawtooth) and squarewave. I did not want to go down the stand voltage controlled oscillator because of frequency drifting due to temperature changes etc. I`m going to get the microprocessor to send out a PWM and then filter it to create a control voltage. I`ve simulated that by the battery you see in the bottom left (0. 6v). You can see the output control values i`ve calculated in the spreadsheet. Are you going to AC-couple the output of your sawtooth generator The reason I ask is that a single-supply op amp, even with rail-to-rail output, can only get within ‰ 100mV of zero volts. If you AC-couple, I suppose that won`t matter. I can show you how to do it with a single supply, but if I post the schematic, On1aag will come up with something with half as many parts, and compare me to Rube Goldberg again. I can show you how to do it with a single...




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