The TPA311 is a bridge-tied load (BTL) or single-ended (SE) audio power amplifier developed especially for low-voltage applications where internal speakers and external earphone operation are required. Operating with a 3.3-V supply, the TPA311 can deliver 250-mW of continuous power into a BTL 8- load at less than 1% THD+N throughout voice band frequencies. Although this device is characterized out to 20 kHz, its operation was optimized for narrower band applications such as cellular communications. The BTL configuration eliminates the need for external coupling capacitors on the output in most applications, which is particularly important for small battery-powered equipment. A unique feature of the TPA311 is that it allows the amplifier to switch from BTL to SE on the fly when an earphone drive is required.