A low-power class-AB negative-feedback output amplifier for a 1 V LW receiver
The design and the measurement results are presented of a low-voltage (1 V) class-AB negative-feedback output amplifier. The amplifier is designed for use in a single-chip LW receiver, which can be put completely in the ear, supplied by a 1 V power supply and is capable of driving a load with an impedance of 30 Omega. The maximum output current of the amplifier is approximately 2.5 mA and its quiescent current is approximately 100 mA. This high efficiency is obtained by means of biasing two of the three amplifying stages in class-AB operation. With the aid of negative feedback, the total harmonic distortion for a single 1 kHz tone at 1 mA level is kept below 1%. The output amplifier is integrated in a bipolar process which has vertical NPN transistors with a maximum f(T) of 5 GHz and lateral PNP transistors with a maximum f(T) of 20 MHz.
low voltage low power systematic analog design