>>2928020
The way I usually do this:
Non inverting schmitt trigger followed by integrator feeds back into the schmitt trigger and also feeds into output comparator.
You set the frequency by adjusting the resistor into your integrator (use pot if you like) and the inverting input of your output comparator comes off a resistive divider to set the duty cycle.
In case my desciption sucks or the principle isnt clear:
The schmitt trigger is either 1 or 0. As such the integrator will creep up or down. Since its output feeds back into your schmitt trigger it will eventually flip it. This will then cause the integrators output to creep into the opposite direction and this repeats ad infinitum. This is how you create an adjustable triangular wave using only one dual comparator for example. If you now feed your triangular wave into a comparator and set its inverting input using a resistive divider you get to set the duty cycle.
Use comparators, 1kHz is easy peasy, two LM311 is all you need and you'll have plenty of room to GO FAST. You'll also have 1 comparator left for other purposes. Do not use OPs, the slew rate is always a pain in the ass. Stay away from 555 shit.
Picrel shows one such thing I whipped up real fast. So all you really need is comparators, a few diodes, resistors and a small cap. Two pots if you want to adjust frequency AND duty. Ignore the added on push pull output stage.