A compact bipolar class AB output stage using 1 V power supply

A compact class AB output stage is described which is able to operate from a supply voltage down to 1 V, delivering an output signal of 400 mV into a 64- Omega load with 1% THD at 1 kHz. Because of the increasing demand for portable audio equipment, it is necessary to drive a headphone from a low supply voltage using low standby current. The class AB output stage shown is the classical solution to this problem. It contains stacked diode pairs in a translinear loop and requires a minimum supply voltage of 2 V/sub be/ and 2 V/sub sat/ voltages. For ease of design, a differential amplifier is chosen as the input stage to increase gain and provide an inverting and a noninverting input. The amplifier was designed to create a 600-Mv/sub pp/ output signal into a 64- Omega load, using a 1.3-V power supply, and to operate at 1-V supply with reduced performance.<>