A power amplifier comprises an input terminal, an output terminal and a first amplification stage coupled with the input and output terminals. The first amplification stage having a node and a resistive structure coupled with the node. The resistive structure includes a first resistive circuit coupled with the node; and an adaptation circuit coupled with the first resistive circuit such that when the first amplification stage is in a first mode, the resistive structure provides a first effective resistance and when the first amplification stage is in a second mode, the resistive structure provides a second effective resistance.