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Simple but Fully Discrete Triangle Wave Generator
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PinePolarBear:
Hello. I'm working on a fully discrete class D amplifier. I'm looking for a triangle wave generator design. It would be preferably simple, but it needs to go above 250 kHz. Thanks.
JPortici:
Component selection and how to get around all the gotchas to achieve an triangle that as pure and symmetric as possible is left as an excercise to the reader
Benta:
You should add that the triangular output is from the first amp.
T3sl4co1l:
I've used some variant of this, many times:

https://www.seventransistorlabs.com/Images/Flashlight2_Schematic.png

IC2 is a astable multivibrator and PWM comparator.  Q4A isn't necessary, but it improves linearity.  If not needed, it can be replaced with a pull-up resistor.

Note that you don't want to skip the rest of the circuit: IC3B compares the inductor current to the current setpoint, providing a first line of defense against destruction of transistors or other components.  The output current simply cannot be anything other than what it can be set to, within a controlled range.  IC3A then controls that current, in order to regulate the output value (in this case, a combination of output current and voltage for driving LEDs, but just voltage would be fine for a power supply or amplifier).

The chained error amplifier topology also avoids putting the double-pole output filter inside a single loop.  Instead, the inductor is in the first loop, and the capacitor and load in the second.  This is much easier to compensate, and gives much nicer waveforms.

Tim
David Hess:
Oscilloscope sweep generators meet your requirements so you might want to study how they work.

I would also consider bipolar implementation of a PUT based relaxation oscillator with the resistance replaced with a constant current source.

https://www.instructables.com/id/Circuit-Collection-of-the-Programmable-Unijunction/
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