A Current Balanced Multi-Phase Class-D Amplifier for Wideband Supply Modulator

Battery-powered mobile communication devices use supply modulator to supply the RF-PA with dynamic voltage for higher efficiency. Conventionally a linear amplifier is used as the fast path in supply modulator to provide ac power to the RF-PA. Class-D amplifier is replacing the linear amplifier for its better efficiency at driving capacitive loading at broader bandwidth. Drivers with multiple phase and level are employed to improve bandwidth and suppress switching noise. Multiple phase class-D amplifier usually equalizes dynamic load currents of the individual output drivers with sophisticated current sensors. In order to reduce the hardware complexity and the power consumption, this paper proposes a current balancing circuit without current sensors. Despite its primary intended application area in class-D amplifier, the current balancing circuit also works for buck converters.