In this paper we present a modulator for an all-digital pulse-width modulated (PWM) transmitter based on switching amplification. In this approach, each symbol is represented by a sequence of pre-computed PWM pulse widths stored in a table that results in reduced Error Vector Magnitude (EVM), achieving low distortion with a reduced pulse-rate. The modulator is implemented in a field programmable gate array (FPGA) device. The performance of this approach is compared to a standard uniform PWM modulator. Measurements using 64-QAM signals show a reduction of EVM values from 11.61% (-18.7 dB) for uniform PWM to 2.41%(-32.4 dB) for the proposed approach.