I. Introduction
Digital components are now frequently found in everyday items, such as compact discs (CDs), digital video discs (DVDs), MP3 players, wireless communications, and others. Sandler [1] proposed the concept of power digital-to-analog conversion in early 1990. Generally, reconstruction of the analog signal requires conversion from the digital domain to the analog domain, followed by inefficient class A or AB amplification. For low-frequency applications, several attempts have been made to implement an efficient power amplifier to directly convert digital input signals to analog without using multibit converters [2], [3]. These works utilized pulse code modulation to pulsewidth modulation (PCM-PWM) or delta-sigma modulators (DSMs) to achieve their requirements. But all of these methods require high-speed computation capabilities. Therefore, in practice, they are not applicable for today's RF applications.