Abstract: This description discloses a circuit board for a power amplifier that is able to keep a low temperature. In an example embodiment, the circuit board includes: an input board on its substrate, an output board on its substrate, and a power amplifier transistor acting as a bridge to connect the input board and the output board with each other. The substrate of the input board is made from a first kind of material, and the substrate of the output board is made from a second kind of material. The second kind of material has different performance (e.g., relatively better performance for both RF and heat dissipation) than that of the first kind of material. Moreover, this description discloses a power amplifier on the circuit board, a dual radio unit board having such a power amplifier, and a radio base station having such a dual radio unit board.