This manuscript reports the design of a switchable low noise power amplifier (LNPA) intended for an active backscatter tag used in microwave localization and positioning applications. Due to system specifications, the backscattering transponder requires an amplifier having both low noise and high output power characteristics at the same time. Low noise amplifier (LNA) and power amplifier (PA) design considerations are both taken into account to realize a single structure achieving the required performances. The proposed LNPA is operating in the frequency range of 4.5 GHz to 5.8 GHz. It achieves a gain of 21 dB with a ripple of ±1 dB, a noise figure (NF) of less than 2.5 dB and an output compression point at -1 dB (OCP1) of 11 dBm over the operational bandwidth. This structure can be switched on and off by a control signal to modulate the tag radar cross section (RCS) and enable distance measurement. A packaged prototype of the LNPA was fabricated and measured.