A transmitter controlling output power to generate a ramp and a method thereof. The transmitter comprises a baseband module, a transmitter module, and a power amplifier. The baseband module receives a power control level, determines a scaling factor according to the power control level, determines a difference between an upper power limit and lower power limit according to a position on the ramp, and calculates a control signal according to the scaling factor, the lower power limit, and the difference. The transmitter module transmits data. The power amplifier coupled to the baseband module and the transmitter module, outputs the data with the output power according the control signal.