For audio output, Thingy has a miniature speaker that is driven from a simple H-bridge amplifier with a PWM input.
A couple of zener diodes minimize the time where both the P-channel and the N-channel MOSFET are turned on at the same time. Power supply for the amplifier comes directly from the battery to maximize the power to the speaker. The power supply is routed through a switch to avoid leakage currents when the speaker is not in use.
Figure 1. Amplifier and speaker schematic
