Pulse Width Modulation (PWM) is a baseband modulation technique which converts an analogue sign to a digital signal. In this technique, if the input signal amplitude is more than the ramp signal, there will be an output pulse with positive peak and a negative peak pulse on the output if the input signal level is below the ramp signal. Therefore, the decision for the output modulated waveform is based on the amplitude of the input signal compared to that of the ramp signal.

In the FlexTrainer, the reference signal is a ramp signal with sampling frequency of 1 kHz that is internally generated by the FlexTrainer and the analog signal may be applied from the signal generator. Figure 1 shows the pulse width modulation of an analog signal.

Figure 1: Pulse width Modulation

At the end of this experiment, students should vary the amplitude of applied analog waveform and observe the change in pulse width modulated signal on the oscilloscope.