Ece 206: pwm and motor speed control pwm (pulse-width modulation) is a convenient way to generate an approximate analog voltage from a digital signal. in a pwm system, the pulse width (sometimes called the "duty cycle") of a constant (base) frequency waveform is changed ("modulated"). the result is sent through a low-pass filter, which removes the high base frequency. this results in an analog voltage being generated at the output of the low-pass filter. notice that the microcontroller only needs to generate digital signals directly (e. g. 0 – 5 v), but the output of the filter is a