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This paper proposes a new phase-locked-loop (PLL)-based inductive coupled contactless energy transfer (CET) analog frequency-shift keying (FSK) demodulator using a high-efficiency RF-to-dc rectifier for biomedical implanted devices. The analog FSK demodulator is composed of a modified CMOS three-stage rectifier, a voltage regulator, an FSK signal generator, and a PLL. The proposed modified single-stage rectifier with both positive and negative output voltages using a PMOS and an NMOS pass transistor, an inverter, and two capacitors has a small active area and can enhance the power conversion efficiency. The proposed RF-to-dc rectifier achieves an efficiency of 64% at 8.4 dBm. The power consumption of the demodulator is as low as 0.76 mW, and the active area is 0.084 mm 2 . The analog FSK demodulator supports a data rate of 100 kb/s to 1 Mb/s. The chip was implemented in a Taiwan Semiconductor Manufacturing Company (TSMC) 0.35-μm double-poly quadruple-metal CMOS technology to verify the proposed CET circuit. Two figures of merit are provided to illustrate the advantages of the proposed architecture. Index Terms-Contactless energy transfer (CET), frequencyshift keying (FSK) demodulator, phase-locked loop (PLL), power conversion efficiency, rectifier.

SUMMARYA new fast-response buck converter using accelerated pulse-width-modulation techniques is proposed in this article. The benefits of the accelerated pulse-width-modulation technique is fast-transient response, simplecompensation design, and no requirement for slope compensation; furthermore, some power management problems are minimized, such as EMI (Electro Magnetic Interference), size, design complexity, and cost. The traditional voltage-mode speed is slower with the transient response, so an accelerated pulse-widthmodulation technique is used to solve the problem of slowed transient response in this article. The proposed buck converter has excellent conversion efficiency with a wide load conditions. The proposed buck converter has been fabricated with TSMC 0.35 mm CMOS 2P4M processes, and the total chip area is 1.32 Â 1.22 mm 2 . Maximum output current is 300 mA when the output voltage equals 1.8 V. When the supply voltage is 3.6 V, the output voltage can be 1-2.6 V. Maximum transient response is less than 5 ms. The simulation and experimental results are presented in this article.

A low-voltage positive buck-boost converter using average-current-controlled techniques is proposed in this paper. The benefit of the average-current-controlled circuit is that it does not need to use slope compensation, furthermore, it can reduce some power management problems such as cost, design complexity, size, and EMI. The advantages of the low-voltage operational amplifier are that it has lower power dynamic consumption and also can operate at low supply voltage. The proposed low-voltage positive buck-boost converter using the active-current-sensing circuit and average-current-controlled circuit techniques can work stably without slope compensation even when the duty cycle is higher than 50%. The proposed design circuit has been fabricated with TSMC 0.35μm CMOS 2P4M processes, the total chip area is 2.46 x 2.47mm 2 . When the supply voltage is 1.5V, the output voltage range is between 0.8V~3.3V.Keyword: Positive buck-boost converter, low supply voltage, low-voltage operational amplifier, average-current-controlled.

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