Envelope Modulator for 1.5-W 10-MHz LTE PA Without AC Coupling Capacitor Achieving 86.5% Peak Efficiency

An envelope modulator (EM) is presented to increase the efficiency of an RF power amplifier. In order to supply an output voltage higher than the input voltage while providing low-frequency power in the EM, a single-inductor dual-output (SIDO) converter is introduced. By employing the SIDO converter, the EM does not require an additional boost converter. In addition, a high-frequency converter (HFC) with a wide-bandwidth capability is also proposed. These two converters, the SIDO converter and the HFC, are combined in parallel without an ac coupling capacitor by employing a low-frequency current-balancing technique. The chip is implemented in a 0.18-μm CMOS process and achieves 86.5% peak efficiency while tracking a 10-MHz long-term evolution envelope signal.