Radio frequency power amplifier for cellular telephones

摘要

A bias circuit having a relatively long time constant improves the linearity of a radio frequency power amplifier of a spread spectrum mobile telephone by causing a power transistor of the amplifier to operate in class A or AB mode. The power amplifier thus derives an output signal that is a substantial replica of the spread spectrum input signal for all amplitudes of the input signal. The bias circuit has transistors connected in a feedback circuit which tends to oscillate to affect the amplifier operation. A low pass filter connected to the transistors suppresses the tendency. An interstage high pass matching circuit between a linear amplifier that drives the power amplifier includes a series capacitor and an inductor connected between an output terminal of the linear amplifier and a DC power supply terminal.