This application uses a custom-made Class D power amplifier (Figure 7-3) to connect an external speaker to the DAC output. A 300 kHz, 95% duty cycle PWM signal is used to generate a sawtooth waveform. This sawtooth waveform, along with the DC-offset DAC signal, is fed into a comparator to generate a PWM waveform. This PWM waveform passes through a MOSFET driver to drive an externally connected speaker. Refer to the TC4428 data sheet for more information about the MOSFET driver.
This Class D power amplifier is implemented as a custom made circuit on a PROTO Click
Board™ (Figure 7-4). The PROTO
Click Board™ also includes a circuit for additional jumpers, switches and a 3.5 mm audio
socket to enhance the functionality of the application.
Figure 1. Class D Power
Amplifier
Figure 2. PROTO Click Board™
Circuit
Figure 3. Full System Setup
