3 Power Supply

An important piece of the output power equation is the supply voltage for the amplifier. Some Class-D amplifiers use one rail and others (bipolar or split-rail amplifiers) use two of equal magnitude, but opposite polarity rails to amplify the audio signal. Aside from this, another rail is typically required for internal logic regulators and gate-drive circuitry, such as 1.8 V, 3.3 V, 5 V, or 12 V. Some newer devices like the TPA322x family integrate a linear drop-off regulator (LDO) internally to produce this rail from the main supply rail. While using the internal LDO isn’t as efficient, it can provide large cost and design savings if the necessary supply voltage isn’t already available in the system. A great use case for single-rail supply amplifiers with an LDO are battery-operated speakers. For systems with a very low supply voltage, from a 1S battery for example, often a boost converter is used to drive the necessary output power. Class-D amplifiers such as TAS2562 even integrate a boost converter for overall system cost and space savings.