A Class-D stage with harmonic suppression and DLL-based phase generation

Abstract

This paper presents a Class-D stage with 3rd harmonic suppression operating at 2VDD(i.e., twice the nominal supply voltage). A DLL-based phase generator is used to generate the phases of the driving signals and by modifying the driver stage 5th harmonic suppression is also possible. The output stage and drivers are based on inverters only, where the short-circuit current is eliminated in the output stage. Operating at 1 GHz, the simulated output power is +19.4 dBm utilizing a 1-V supply and a 5-Ω load, with Drain Efficiency (DE) and Power-Added Efficiency (PAE) of 72% and 52%, respectively, including power dissipation in the DLL-based phase generator and drivers. The 3rd harmonic is suppressed 23 dB (-33 dBc) compared to a conventional Class-D stage.