Can 2 XR-2206 function gen and a LM-339 quad comparator be used to generate pulse width modulation? How?

Question

Have used 2 XR-2206 (Monolithic

Function Generator) to generate a sine & a triangular wave respectively. Tried to connect them directly to a LM-339 quad comparator to get a pulse width modulation (pwm) but to no avail. How can I generate the pwm using the 2 XR-2206 and the LM-339? Do I have to add any other equipment? Is it possible to get the pwm using just the mentioned equipments?

Answer 1

Yes. Set the FG to output a triangular wave of 0 to 10 volts, and apply to + input of the 339.

The other input to an adjustable DC voltage adjustable from 0 to 10 volts. This can be a 1k pot from +10 to ground, slider to - input. This adjusts the duty cycle.

Connect +10 to 339 supply pin. Output of 339 to +10 via a 1k resistor.

To improve the performance at the switch point, add a 10k R in series with the + input and a 1M R between + input and the output.

The use of +10 is just an example, it will operate with supply voltage from 5 to 30 volts.

PS, you need only one FG.

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