A receiver is disclosed. The receiver includes: a tunable low noise amplifier (LNA), the tunable LNA comprising: a plurality of LNAs for receiving and amplifying a plurality of frequency bands respectively; a plurality of first switches respectively coupled to the plurality of LNAs; a plurality of LC loads, respectively coupled to the plurality of first switches; a plurality of buffers, respectively coupled to the plurality of first switches; and a plurality of second switches, respectively coupled to the plurality of LC loads and an LO signal; a power detecting circuit for determining a signal power level corresponding to the LO signal; a first switch unit; and a controller, for isolating the output of the plurality of LNAs, selectively decoupling at least one of the LC loads according to the signal power level of the LO signal, and routing the LO signal to the second switches during calibration mode.