This paper presents the design and linearization of hign efficiency dual mode amplifier. A dual mode transmitter requires an mplifier which generates different output level for different applcations. For WiBro, the output is 1 W at 2.3GHz, andfor wireless LAN the output is less than lOOmW at 2. 4GHz, A bias switching amplifier is designed to get the higher efficiency at both applications With bias switching the amplifier shows the efficiency improvement of up to 25% point. This paper also shows the possibility of linearity improvement for the dual mode amplifier by using predistortion techniquea