What's the easiest way to generate a square/rectangular wave using a simple circuit? It will be used to pulse a motor, and I need to be able to alter the duty cycle of the rectangular waveform from 5% to 95% using a potentiometer, where duty cycle ∝ voltage. My power supply is 3.3V, so I'm limited to BJTs for transistors. Any suggestions?
Edit 1: Most of my attempts have been starting with an RC circuit and trying to use BJTs to set the output high when the cap is charged, which causes the cap to discharge and start again, or something along those lines.
Edit 2: A 555 timer wouldn't allow me to have the duty cycle directly proportional to the voltage on the pot.
Edit 3: In the end I decided on a LTC6992 PWM IC, as it provides the most accuracy, and doesn't take up much space.