The demodulation of pulse width modulated signal is carried out by extracting the low frequency component of the modulated signal. The transitions in the modulated signal are the high frequency components. A low pass filter can be employed to extract the analog signal from the modulated signal. Figure 1 shows the block diagram of the pulse width demodulator.

Figure 1: Block diagram of pulse width demodulator

The result of application of a low pass filter on the pulse width modulated signal is shown in Figure 2. 

Figure 2: Pulse width demodulation

At the end of this experiment, students are instructed to apply pulse width demodulation technique to different analog waveforms and observe the results on the oscilloscope.