Efficient, low-distortion switch-mode power amplifier for amplitude modulation

Abstract

Amplitude modulation systems are used in many areas of engineering, especially communication based disciplines. Typical systems have low-level signals which encode the desired information to be transmitted. These low-level signals are usually not of adequate power to transmit the desired information across a target medium, thus requiring modulation and power amplification. In general, two goals of power amplifier design are low-distortion and high-efficiency. To meet these goals, a unique switch-mode power amplifier intended for amplitude modulation which utilizes spectral content at the carrier frequency is designed, simulated, and built. Theoretical predictions of total harmonic distortion (THD) and efficiency are made, and the constructed prototype results are measured. The THD for a 1 kHz modulating tone is predicted to be 0.9% and measured to be 4.15% worst case. The amplifier output stage efficiency is predicted to be 95.8% and measured to be 95.4% worst case.