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In this paper, we present a CMOS full-wave rectifier with comparator-controlled switches for transmission of wireless power in implantable medical devices. It uses MOS transistors as low loss switches to provide high power conversion efficiency (PCE). The proposed fast comparator circuit, by controlling the switches in the rectifier, reduces the reverse leakage current in the negative cycle and increases the conduction time in the positive cycle so that more current flows into the output load and optimizes the rectifier power efficiency. The designed comparator does not require constant voltage source for its function and it is self-biased. The proposed rectifier is implemented using 0.18 μ m CMOS technology and provides 1.195 V output DC voltage with a 190 Ω load resistance and AC input signal with the frequency of 13.56 MHz and peak-to-peak amplitude of 1.36 V. Under these conditions, PCE and voltage conversion efficiency (VCE) values are 85.5% and 88%, respectively. The peak PCE and VCE increase with a decrease in operation frequency and dimensions of transistors are optimized using multiple simulations for intended frequency. [ABSTRACT FROM AUTHOR]

In this paper, we use bias current boosting and slew rate enhancement in multiple-output Low-dropout structure to achieve a faster transient response. This method reduces ripples of output voltage during sudden changes in load current and input voltage. The proposed MOLDO circuit was simulated with a 0.18m CMOS process in buck mode with four-output legs. Integrating of proposed circuit is easier because there is the symmetry in the circuit designing. The results of our work show that when input voltage changes between 2.5-3.3V, the output voltage after 25s with load current of 100mA, is determined with ripple less than 1.8mV. In sudden changes, the load current at the range 0-100mA, and output voltages after a maximum 15.5s with an input voltage of 3.3V have the highest ripple in output voltage of 4mV. [ABSTRACT FROM AUTHOR]