PWM signal vs analog signal.

Pulse-width modulation (PWM), also known as pulse-duration modulation (PDM) is a technique of modulating the duration of the HIGH and LOW pulses of a digital signal. A PWM signal is a way of representing an analog signal in a digital circuit. The application of pulse-width modulation varies greatly from communication and encoding to controlling the power delivered to an external device such as a motor or an LED. The purpose of pulse-width modulation is to vary the duty cycle according to $$\text{duty_cycle} = t_{on}f(t) = \frac{t_{on}}{t_{on}+t_{off}}$$ where the duty_cycle can be controlled by varying \( t_{on} \) or \( t_{off} \).