| 摘要 |
The power amplifier comprises an amplification section (28) containing a power amplification circuit (42) having three amplification stages (422,423,425) and a signal transmission section (58), and a polarization circuit (40); and an output matching circuit (36). When a mode selection voltage (Vmod2) is at low level, an input signal is amplified by the three amplification stages, and the signal transmission section (58) does not transmit any signal. When the mode selection voltage (Vmod2) is at high level, the signal transmission section (58) transmits the input signal (IN1800) to a transistor (Tr2) by the intermediary of a diode (D1), a control votlage (Vmod1800) is at low level and the first amplification stage (422) is blocked thus reducing the power consumption. The signal transmission section (58) comprises a switching circuit connected between two internal nodes, two capacitors and a resistor. The switching circuit is controlled to be in conducting state or non-conducting state with respect to the input signal according to the mode selection signal. The switching circuit comprises a diode (D1), or a transistor connected as a diode. The power amplifier (claimed) is in 8 embodiments. In the embodiments other than the first, the power amplifier comprises an additional inductor connected between the second internal node of the signal transmssion circuit and the ground, an additional diode, or an additional matching circuit between the first and the second amplification stages. The first and the second amplification elements are transistors of type heterojunction bipolar transistor (HBT).
|
