High peak-to-average ratio of OFDM signals requires large back-off from an RF power amplifier's saturation power. A spectral shaper device therefore increases the output power and efficiency of the power amplifier. The shaper device performs linearization through digital predistortion, based on an out-of-band regrowth limit, as well as the EVM requirement for a particular data rate. The shaper can distribute the error energy, precisely, over frequencies such that each of the inband and out-of-band requirements is independently and individually met. The shaper distributes error energy to frequency regions in the spectrum to the maximally allowed by the standards and regulations, while not increasing the total error. The error energy is kept to the minimum where it is crucial in meeting EVM requirements. In this way, the shaper maximizes the allowable output power of the nonlinear power amplifier.