Power amplifier
A power amplifier includes: an amplifying transistor; a bias circuit; a first diode; a second diode; a matching attenuating circuit; a first current mirror circuit; a serial resonant circuit, and a switch. In an amplification mode, the bias circuit supplies a bias current to the amplifying transistor, and the first current mirror circuit turns off the first and second diodes, and the switch. In an attenuation mode, the bias circuit supplies no bias current to the amplifying transistor, and the first current mirror circuit turns on the first and second diodes and the switch.
1. A power amplifier comprising:
an amplifying transistor for amplifying RF signals, having a base connected to an input terminal and a collector connected to an output terminal;
a bias circuit for supplying a bias current to the base of said amplifying transistor;
first and second capacitors and first and second inductors;
a first diode having an anode and a cathode, the cathode being connected to the input terminal via said first capacitor;
a second diode having an anode and a cathode, the anode being connected to the output terminal via said second capacitor, and connected to a first power terminal via said first inductor;
a matching attenuating circuit connected between the anode of said first diode and the cathode of said second diode, for reducing impedance mismatch at the input terminal and at the output terminal, and attenuating the RF signals;
a first current mirror circuit connected to the cathode of said first diode via said second inductor, for driving said first and second diodes;
a serial resonant circuit connected between the base of said amplifying transistor and a grounding point, and having a resonance frequency within an operating frequency band of said amplifying transistor, and
a switch connected between said serial resonant circuit and the grounding point, wherein,
in an amplification mode, said bias circuit supplies the bias current to said amplifying transistor, and said first current mirror circuit turns off said first and second diodes and said switch, and
in an attenuation mode, said bias circuit supplies no bias current to said amplifying transistor, and said first current mirror circuit turns on said first and second diodes and said switch.
2. The power amplifier according to claim 1 , wherein said switch comprises:
a third diode having an anode and a cathode, the anode being connected to said serial resonant circuit, and the cathode being connected to the grounding point; and
a resistor connected between the anode of said third diode and a control terminal wherein a low-level voltage is applied in the amplification mode to the control terminal, and a high-level voltage is applied to the control terminal in the attenuation mode.
3. The power amplifier according to claim 1 , wherein said switch comprises:
a third diode having an anode and a cathode, the anode being connected to said serial resonant circuit;
a resistor connected between the anode of said third diode and a second power terminal; and
a second current mirror circuit connected to the cathode of said third diode, for driving said third diode, wherein
in the amplification mode, said second current mirror circuit turns off said third diode, and
in the attenuation mode, said second current mirror circuit turns on said third diode.