A transmitter includes a power amplifier which is capable of both linear and non-linear operation, controlled by first and second control loops. A power controller includes a capacitive component, and controls the gain of the power amplifier. A ramp generation circuit provides a control signal to the power controller. It includes a ROM which stores ramp data values based on samples of a predetermined ramp shape. The ramp shape is based on a generally regular profile C, for example a cos.sup.2 or cos.sup.4 function. The ramp shape also includes a boost portion BAP, which enhances the ramp data values before the beginning of the generally regular profile C. The boost portion BAP causes the capacitor in the feedback loop of the relevant control loop to become fully charged more rapidly, which produces a corresponding increase in the output power of the power amplifier shortly after the generally regular profile C is applied. This allows the transmitter to follow the generally regular profile C of the ramp signal at an earlier time when compared with the prior art. The size of the boost portion BAP can be adjusted dependent on a detected temperature.