In 2008 this thread was active:
https://www.electro-tech-online.com...ed-oscillator-dco-design-help-required.86601/
It describes a way to construct a DCO. I built this circuit but cannot find out why the generated sawtooth is "wobbly". A video to illustrate:
https://www.youtube.com/watch?v=uWog4BIQmK8
This is my schematic (LTSpice):
**broken link removed**
Halfway during the video I touch R3 to demonstrate the wobble some more. R3 seems to be the problem. I added 0.22µF + 2.2µF bypass capacitors to the opamp (Schematic says TL071 but I used a dual opamp LM833 powered by +/- 15V) but the sawtooth is still too distorted. I tried buffering, capacitors in series etc all to no avail.
The PWM is generated by a LeafLabs Maple r5 board. This board GND is connected to the main GND. The control voltage for the sawtooth is generated by a MCP4921 12bit DAC.
I'm kinda out of ideas now, anyone?
https://www.electro-tech-online.com...ed-oscillator-dco-design-help-required.86601/
It describes a way to construct a DCO. I built this circuit but cannot find out why the generated sawtooth is "wobbly". A video to illustrate:
https://www.youtube.com/watch?v=uWog4BIQmK8
This is my schematic (LTSpice):
**broken link removed**
Halfway during the video I touch R3 to demonstrate the wobble some more. R3 seems to be the problem. I added 0.22µF + 2.2µF bypass capacitors to the opamp (Schematic says TL071 but I used a dual opamp LM833 powered by +/- 15V) but the sawtooth is still too distorted. I tried buffering, capacitors in series etc all to no avail.
The PWM is generated by a LeafLabs Maple r5 board. This board GND is connected to the main GND. The control voltage for the sawtooth is generated by a MCP4921 12bit DAC.
I'm kinda out of ideas now, anyone?
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