variable pulse generator

Many digital applications require the use of a pulse generator of which not only the frequency, but also the duty-cycle can be varied. A problem with certain simple variable pulse generators is that altering the duty-cycle also affects the frequency of the output signal. The circuit described here, however, which uses only a handful of components, is free from this drawback; both frequency and duty-cycle are independently variable. The frequency range extends from approx. 1 kHz to 20 kHz, whilst the duty-cycle can be varied from almost Oto 100%.