Abstract-This paper presents a low-dropout regulator (LDO) for portable applications with an impedance-attenuated buffer for driving the pass device. Dynamically-biased shunt feedback is proposed in the buffer to lower its output resistance such that the pole at the gate of the pass device is pushed to high frequencies without dissipating large quiescent current. By employing the current-buffer compensation, only a single pole is realized within the regulation loop unity-gain bandwidth and over 65 phase margin is achieved under the full range of the load current in the LDO. The LDO thus achieves stability without using any low-frequency zero. The maximum output-voltage variation can be minimized during load transients even if a small output capacitor is used.The

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This paper presents an efficiency-enhanced integrated full-wave CMOS rectifier for the transcutaneous power transmission in high-current biomedical implants. The comparator-controlled switches are developed to minimize the voltage drop along the conducting path while achieving the unidirectional current flow. The proposed unbalanced-biasing scheme also minimizes the reverse leakage current of the rectifier under different input amplitudes, thereby optimizing the rectifier power efficiency. Moreover, the proposed rectifier is able to self start and operates at low input amplitudes. Implemented in a standard 0.35 m CMOS process with maximum threshold voltages of thp = 0 82 V and thn = 0 69 V, the rectifier can source a maximum output current of 20 mA and operate properly with inputs of different amplitudes and frequencies. With a 1.5 MHz input of 1.2 V amplitude, the proposed rectifier can achieve the peak voltage conversion ratio of 95% and the power efficiency of at least 82%.

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A fully integrated soft-start circuit for voltage regulators is presented in this brief. A soft-start strategy based on a linearly ramped-up reference is adopted to prevent massive inrush currents through the power device during the start-up phase of the regulator. The strategy is realized by a compact on-chip circuit, which requires no external components and has minimal transistor overhead, thereby minimizing the implementation area and cost of the overall regulator. The proposed soft-start circuit has been implemented in a 0.35-μm high-voltage complementary metal-oxide-semiconductor technology as part of a linear regulator controller for automotive applications. The proposed soft-start circuit occupies 0.026 mm 2 on silicon, which corresponds to about one fifteenth of the total area of the linear regulator controller.Index Terms-Linear regulator, low-dropout regulator (LDO), power management integrated circuits, soft start, switching regulator, voltage regulators.

Abstract-This paper presents a low-power stability strategy to significantly reduce the power consumption of a three-stage amplifier using active-feedback frequency compensation (AFFC). The bandwidth of the amplifier can also be enhanced. Simulation results verify that the power dissipation of the AFFC amplifier is reduced by 43% and the bandwidth is improved by 32.5% by using the proposed stability strategy. In addition, a dynamic feedforward stage (DFS), which can be embedded into the AFFC amplifier to improve the transient responses without consuming extra power, is proposed. Implemented in a 0.6-m CMOS process, experimental results show that both AFFC amplifiers with and without DFS achieve almost the same small-signal performances while the amplifier with DFS improves both the negative slew rate and negative 1% settling time by two times.Index Terms-Active feedback, amplifiers, dynamic feedforward stage (DFS), frequency compensation, low-power stability strategy, multistage amplifiers.

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