1. A transmission unit comprising:a power amplification circuit configured to amplify a power of an input signal and to output an amplified signal; and
a power supply circuit configured to supply a power supply voltage to the power amplification circuit based on a first control signal that corresponds to a band width of the input signal,
wherein the power supply circuit is configured to:
vary the power supply voltage in accordance with an amplitude level of the input signal when the band width of the input signal is a first band width, and
vary the power supply voltage in accordance with an average output power of the power amplification circuit when the band width of the input signal is a second band width,
wherein the second band width is larger than the first band width.