A PWM generator is a device that can generate a PWM signal according to its internal settings. The output of a PWM generator is just a sequence of pulse signals as a square waveform with well-defined characteristics:
By referring to the preceding graph, where we have a simple PWM waveform, we can define the following parameters:
Amplitude (A): This is the difference between the maximum output value (ymax ) and the minimum one (ymin ).
Period (T): This is the duration of one cycle of the output square waveform.
Duty-cycle (dc): This is the ratio in percentage between the high state time (thigh ) and the period (T).
In our example in the preceding graph, the amplitude is 5V (ymax=5V and ymin=0V), the period is 1ms (the wave is periodic, and it repeats itself every 0.001 seconds), and the duty-cycle is 25 percent (thigh=0.25ms and T=1ms).
Note
You can find details about PWM at https://en.wikipedia.org/wiki/Pulse-width_modulation .