This paper introduces a new envelope tracking power supply to enhance the performance and reduce the overall volume of transmitter modules. The realization is based on a gyrator resonant switched-capacitor converter (GRSCC) that acts as a controlled bi-directional current source with a virtually instantaneous response to create the desired envelope. A quasi-non-casual control method is further applied to closely track high-rate signals without further increasing the switching frequency. The resultant dynamic performance for a given envelope reference signal is significantly improved, providing envelope supply voltage without clipping distortion. Design example and simulations are detailed, and the operation of envelope tracker is verified on a 150mW prototype switched at 2.3MHz, able to track a 1MHz envelope with less than half the losses of a linear regulator.