Current-mode class-D power amplifiers for high-efficiency RF applications

We show that current-mode class-D (CMCD) power amplifiers can achieve high efficiency at RF frequencies. In contrast with conventional voltage-mode class-D amplifiers, the CMCD features zero voltage switching, which eliminates the output capacitance discharge loss. Experimental CMCD amplifiers with 76.3% power-added efficiency (PAE) at 290-mW output and 71.3% PAE at 870-mW output are demonstrated using GaAs FETs at 900 MHz.