The first example uses the standard op-amp oscillator circuit to generate a triangular waveform which is level-shifted and fed to a comparator (e.g. LM339) to give the PWM waveform. Most people will want to use two comparators rather than one op-amp and one comparator so that is what we show here.
Related Links Circuits
More about Electronic Control
More Motor Speed Controller
More about Pulse Width Modulated
More about PWM speed motor
More about LM339
Read More Source:
http://www.4qdtec.com/pwmmod.html
Thank you.
