A mobile system has a frequency synthesizer and an amplifier module coupled to the frequency synthesizer. The frequency synthesizer is controlled by frequency division data to generate a tuning signal with a frequency corresponding to a reference signal and the frequency division data. The mobile system provides an input signal based on the frequency of the tuning signal having a frequency spectrum corresponding to the frequency of the tuning signal. The amplifier module has a variable load circuit for providing an equivalent impedance, an amplifier circuit coupled to the variable load circuit for establishing an output signal corresponding to the input signal and the equivalent impedance of the variable load circuit, and a mapping circuit for modifying the equivalent impedance of the variable load circuit based on the frequency division data.