A pulse width modulator (PWM) generates the binary data from an analog signal. It has a analog signal input (v<sub>s</sub>) and another input for a ramp generator (v<sub>ramp</sub>). The PWM basically consists of a voltage comparator that compares the ramp and input signals. The binary output is given by:
<math> v_{out} = \begin{array}{ll} V_{High}, & v_s > v_{ramp} \\
V_{Low}, & v_s < v_{ramp} \end{array} </math>