| 摘要 |
The amplifier comprises two power amplifiers, two polarization circuits, a polarization switching circuit together with three switching circuits for controlling the polarization and the selection and operation of the switching. The double-band power amplifier comprises two power amplifiers (2,4), each containing at least one heterojunction bipolar transistor (11,21) for power amplification, two polarization circuits (3,5), one for each power amplifier and containing heterojunction bipolar transistors, and a polarization switching circuit (6) for the selection of one switching operation according to the first and second input signals. The polarization switching circuit (6) contains first and second switching circuits, each with a heterojunction bipolar transistor, for the control of output of first signal for the control of one or other polarization circuit (3,5), respectively, and a third switching circuit with a heterojunction bipolar transistor for the control of the second switching circuit according to the second signal for the control of the first switching circuit and the selection of the first or second switching circuit. Each of the two switching circuits, first and second, comprises resistors connected in series for dividing the voltage (Vpc), and a heterojunction bipolar transistor connected to the ground, for delivering a control signal to one of the two polarization circuits (3,5). Each power amplifier (2,4) contains several amplifier stages and several heterojunction bipolar transistors for power amplification. Each polarization circuit delivers a biasing voltage to each heterojunction bipolar transistor, and two switching circuits deliver control signals to the polarization circuits gradually increasing the electric current from the first to the last amplifier stage. Each of the two switching circuits also contains at least one adjustable resistor connected in parallel for the level of control signal. The third switching circuit contains a heterojunction bipolar transistor for the control of the second switching circuit via base biasing accordance to the second input signal. In a variant of the power amplifier, the two switching circuits also contain circuits for the protection of each polarization circuit from a surge of voltage applied to the first input; each protection circuit is a base-emitter voltage multiplier containing a heterojunction bipolar transistor.
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