Making a PWM frequency generator using general purpose transistor

[Fragrance]

Hi

Can i amde a pwm frequency generator using general purpose transistor i would be great full if any good idea come up

regards
Fragrance

 

[plusminus]

Re: Any Idea About PWM

First make a linear-ramp generator. Make a constant current source charging a capacitor and decharge it directly by shorten the capacitor with a transistor. The transistor conducts at the maximum voltage of the ramp. (1/Charge time) is PWM frequency. You can also decharge the capacitor with a transistor and a resistor (same current as charge current) to make a symetrical PWM signal. (PWM frequency is (1/(charge+decharge time)) )

Then feed the ramp generator to the minus input of a discrete build voltage comparator circuit.

Make a regulated voltage source (potentiometer) and feed this to the plus of the comparator circuit. The voltage maximum and minimum should be the same as the voltage if the ramp.

The output of your comparator circuit is a PWM signal.

A lot of work to make discrete but possible.