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

This paper presents a Class-D stage with 3rd harmonic suppression operating at 2V_DD(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 5^th 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.