High-frequency amplifier

A high-frequency amplifier comprising:

• a driver amplifier configured to amplify an input high-frequency signal;
• a Doherty amplifier, including a carrier amplifier and a peak amplifier, and configured to further amplify a signal output from the driver amplifier;
• a first multilayer substrate;
• a second multilayer substrate laminated to overlap the first multilayer substrate;
• and
• a base member mounted with the first multilayer substrate and the second multilayer substrate, wherein:
• the driver amplifier is mounted on the second multilayer substrate,
• the carrier amplifier and the peak amplifier are mounted on the first multilayer substrate,
• the driver amplifier, the carrier amplifier, and the peak amplifier have a front surface forming a predetermined circuit, and a back surface located on an opposite side from the front surface, respectively,
• the front surface of the driver amplifier opposes the first multilayer substrate, and the back surface of the driver amplifier is separated from the first multilayer substrate,
• the back surfaces of the carrier amplifier and the peak amplifier both make contact with the base member, respectively, and
• the back surface of the driver amplifier is connected to a first interconnect layer disposed on a surface of the second multilayer substrate, the first interconnect layer is connected to one end of a first via penetrating the second multilayer substrate and the first multilayer substrate, and the other end of the first via is connected to the base member.