Power Amplifier incorporating single drain switch and single negative voltage generator

A multiband power amplifier system for amplifying a radio frequency (RF) signal having one of a plurality of preselected frequencies comprising:

• a first power amplifier having a signal input for receiving an RF signal of a first preselected frequency and amplifying said RF signal to produce an amplified RF signal at an output terminal, and a control input for receiving a control signal;
• a second power amplifier having a signal input for receiving an RF signal of a second preselected frequency to produce an amplified RF signal at an output terminal, and a control input for receiving a control signal;
• means for coupling said output terminals of said first and second power amplifiers at a common node;
• controller means for providing a first control signal to said first power amplifier control input and a second control signal to said second power amplifier control input for activating in a first mode, and for deactivating in a second mode, said respective power amplifiers;
• and
• a switching device having a first terminal coupled to the output of each of said first and second power amplifiers at said common node and capacitively coupled to a reference potential at said first terminal, and a second terminal coupled to a power source, said switching device responsive to a control signal from said controller means for providing a high impedance at the output of said first and second power amplifiers when said power amplifiers are deactivated, and for enabling current to be drawn from said power source to an active power amplifier to enable amplification of said RF signal of preselected frequency.

A dual band power amplifier circuit comprising:

• first and second power amplifiers each operative to amplify an RF signal of a particular frequency range at an output terminal thereof, wherein said output terminals of said amplifiers are coupled together at a common node, and wherein said amplifiers are operative in a first saturation mode and in a second linear mode;
• a control circuit for providing a first control signal to said first power amplifier and a second control signal to said second power amplifier for controlling the mode of operation of each said amplifier;
• and
• a switching device having a first terminal coupled to the outputs of said first and second power amplifiers at said common node and to a power source at a second terminal, said switching device responsive to a third control signal from said control circuit for providing a high output impedance to said amplifiers for limiting leakage current when said first and second amplifiers are in said saturation mode, and for enabling current to be drawn from said power source to a particular one of said power amplifiers when said particular power amplifier is in said linear mode.