| 摘要 |
The present invention relates to a power amplifier which guarantees an isolation function of two power amplification paths and reduces the circuit loss. First and second amplifiers (A1, A2) are connected in between an input terminal (IN) and an output terminal (OUT). A first contact point (P1) is formed in between the input terminal (IN) and input of the amplifiers (A1, A2). A second contact point (P2) is formed in between the output terminal (OUT) and output of the amplifiers (A1, A2). The second contact point (P2) is a point which an impedance starts to decrease in a path from the input terminal (IN) to the output terminal (OUT) through the two amplifiers (A1, A2). A third amplifier (A3) is connected in parallel with the first and second amplifiers (A1, A2) in between the first and second contact points (P1, P2). A third contact point (P3) is formed in between an output of the third amplifier (A3) and the second contact point (P2). A first capacitor (C1) is connected in between the third contact point (P3) and ground. A switch (SW) is connected in serial to the first capacitor (C1) in between the third contact point (P3) and ground. The switch (SW) is turned off when the third amplifier is turned on, and is turned on when the first and second amplifiers (A1, A2) are turned on. |
