Carrier aggregation circuit allowing carrier waves with different frequencies to share the same amplifier

A carrier aggregation circuit includes a signal input terminal, a signal output terminal, a first filter, a first output transform circuit, a second filter, and a second output transform circuit. The signal input terminal receives a radio frequency signal with carrier waves with first and second carrier wave frequencies. The first filter and the second filter are coupled between the signal input terminal and the signal output terminal respectively, and can respectively filter out signals with frequencies other than the first and the second carrier wave frequencies. The first output transform circuit is coupled between the first filter and the signal output terminal, and has an output impedance equivalent to an open circuit at the second carrier frequency. The second output transform circuit is coupled between the second filter and the signal output terminal, and has an output impedance equivalent to an open circuit at the first carrier frequency.