A transmitter/receiver for a wireless communication system is provided. The transmitter for a wireless communication system includes: an external amplifier connected to a next stage of a power amplifier amplifying a signal to be transmitted to a required power level; a transmission selector configured to directly output the signal amplified by the power amplifier to an antenna or control the external amplifier to amplify the signal, based on a mode control signal; and a mode selector configured to compare a power level of a signal provided from a receiver with a predetermined power level to generate the mode control signal for determining whether or not to operate the external amplifier.