Patent ID: 7907009

Claim:
A high frequency amplifier, comprising: a first amplifying element for amplifying a high frequency signal input from an input terminal; a second amplifying element for amplifying the high frequency signal, which is connected in parallel to the first amplifying element and has a smaller element size than the first amplifying element has; a first bias control circuit for turning on and off the first amplifying element based on a mode switching voltage for switching between a case where an output power is high and a case where the output power is low; a second bias control circuit for turning on and off the second amplifying element based on the mode switching voltage; and an output matching circuit connected to output sides of the first amplifying element and the second amplifying element, the output matching circuit comprising: a first matching circuit connected to the output side of the first amplifying element; a second matching circuit connected to the output side of the second amplifying element; and a third matching circuit connected between an output terminal and a connection node of the output sides of the first matching circuit and the second matching circuit, which is matched to 50 ohms, wherein: the first matching circuit comprises: a low pass filter type matching circuit connected to the output side of the first amplifying element; and a first serial inductor connected to the low pass filter type matching circuit; the second matching circuit comprises: a high pass filter type matching circuit connected to the output side of the second amplifying element; and a second serial inductor connected to the high pass filter type matching circuit; a first impedance of the first matching circuit viewed from the connection node in the case where the output power is high that is a case where the first amplifying element is turned on while the second amplifying element is turned off is substantially the same as a second impedance of the second matching circuit viewed from the connection node in the case where the output power is low that is a case where the second amplifying element is turned on while the first amplifying element is turned off; the second impedance of the second matching circuit viewed from the connection node is higher than the first impedance of the first matching circuit viewed from the connection node in the case where the output power is high that is the case where the first amplifying element is turned on while the second amplifying element is turned off; and the first impedance of the first matching circuit viewed from the connection node is higher than the second impedance of the second matching circuit viewed from the connection node in the case where the output power is low that is the case where the second amplifying element is turned on while the first amplifying element is turned off.