High frequency power amplifier, high frequency power amplifier module, and portable telephone

A high frequency power amplifier comprising:

• an input terminal inputted with a high frequency signal to be amplified;
• an output terminal for outputting an amplified high frequency signal;
• a first amplifying circuit including a first transistor for amplifying the signal inputted to the input terminal, a second transistor for amplifying an output signal of the first transistor, a first matching circuit connected between an output of the first transistor and an input of the second transistor, a second matching circuit connected between an output of the second transistor and the output terminal and at least one piece of a switching circuit connected between a signal line constituted by the first transistor and the second transistor and a ground terminal;
• and
• a second amplifying circuit including a third transistor for amplifying the high frequency signal inputted to the input terminal, a fourth transistor for amplifying an output signal of the third transistor, a third matching circuit connected between an output of the third transistor and an input of the fourth transistor and a fourth matching circuit connected between an output of the fourth transistor and the output terminal,
• wherein the fourth transistor is provided with a size equal to or smaller than ¼ of a size of the second transistor,
• wherein the first and the second transistors output a high frequency signal at a first power level when the third and the fourth transistors are brought into a nonoperational state and the at least one piece of the switching circuit is made off, and
• wherein the third and the fourth transistors output a high frequency signal at a second power level smaller than the first output level when the first and the second transistors are brought into the nonoperational state and the at least one piece of the switching circuit is made on.

A high frequency power amplifier comprising:

• an input terminal inputted with a high frequency signal to be amplified;
• an output terminal for outputting an amplified high frequency signal;
• a first amplifying circuit including a first transistor for amplifying the signal inputted to the input terminal, a second transistor for amplifying an output signal of the first transistor, a first matching circuit connected between an output of the first transistor and an input of the second transistor, a second matching circuit connected between an output of the second transistor and the output terminal and at least one piece of a switching circuit connected between an input terminal of the second transistor or a signal node in the first matching circuit and a ground terminal;
• and
• a second amplifying circuit including a third transistor for amplifying the high frequency signal inputted to the input terminal, a fourth transistor for amplifying an output signal of the third transistor, a third matching circuit connected between an output of the third transistor and an input of the fourth transistor and a fourth matching circuit connected between an output of the fourth transistor and the output terminal,
• wherein the fourth transistor is provided with a size equal to or smaller than ¼ of a size of the second transistor,
• wherein the first and the second transistors output a high frequency signal at a first power level when the third and the fourth transistors are brought into a nonoperational state and the at least one piece of the switching circuit is made off, and
• wherein the third and the fourth transistors output a high frequency signal at a second power level smaller than the first output level when the first and the second transistors are brought into the nonoperational state and the at least one piece of the switching circuit is made on.