Current Issue : July - September Volume : 2017 Issue Number : 3 Articles : 6 Articles
This paper describes a novel energy-efficient, high-speed ADC architecture\ncombining a flash ADC and a TDC. A high conversion rate can be obtained\nowing to the flash coarse ADC, and low-power dissipation can be attained\nusing the TDC as a fine ADC. Moreover, a capacitive coupled ramp circuit is\nproposed to achieve high linearity. A test chip was fabricated using 65-nm\ndigital CMOS technology. The test chip demonstrated a high sampling frequency\nof 500 MHz and a low-power dissipation of 2.0 mW, resulting in a low\nFOM of 32 fJ/conversion-step....
A low-power, low-phase-noise quadrature oscillator for Medical Implantable\nCommunications Service (MICS) transceivers is presented. The proposed quadrature oscillator\ngenerates 349~689 MHz I/Q (In-phase and Quadrature) signals covering the MICS band.\nThe oscillator is based on a differential pair with positive feedback. Each delay cell consists of a few\ntransistors enabling lower voltage operation. Since the oscillator is very sensitive to disturbances in\nthe supply voltage and ground, a self-bias circuit for isolating the voltage disturbance is proposed to\nachieve bias voltages which can track the disturbances from the supply and ground. The oscillation\nfrequency, which is controlled by the bias voltages, is less sensitive to the supply and ground noise,\nand a low phase noise is achieved. The chip is fabricated in the UMC (United Microelectronics\nCorporation) 0.18 Ã?¼m CMOS (Complementary Metal Oxide Semiconductor) process; the core just\noccupies a 28.5 Ã?â?? 22 Ã?¼m2 area. The measured phase noise is âË?â??108.45 dBc/Hz at a 1 MHz offset with a\ncenter frequency of 540 MHz. The gain of the oscillator is 0.309 MHz/mV with a control voltage from\n0 V to 1.1 V. The circuit can work with a supply voltage as low as 1.2 V and the power consumption\nis only 0.46 mW at a 1.8 V supply voltage....
This paper presents a new compact controllable impedance multiplier using CMOS technology. The design is based on the use\nof the translinear principle using MOSFETs in subthreshold region.The value of the impedance will be controlled using the bias\ncurrents only.The impedance can be scaled up and down as required.The functionality of the proposed design was confirmed by\nsimulation using BSIM3V3MOSmodel in Tanner Tspice 0.18 ...
This paper presents a sensitivity-enhanced gas sensor based on a film bulk acoustic\nresonator (FBAR). It was designed and fabricated with micro through-holes in its top electrode\nfor sensitivity enhancement. The sensor was driven by a Colpitts oscillator circuit, and the output\nsignal had characteristics of a power of âË?â??2.6 dBm@3 V and a phase noise of âË?â??90 dBc/Hz@100 kHz.\nIn order to test the performance of the sensor, it was used for the detection of relative humidity\n(RH) and ethanol. When the relative humidity ranged from 25% to 88%, the frequency shift of\nthe sensor was 733 kHz, which was 3.2 times higher than that of the existing FBAR sensor with a\ncomplete top electrode. Fitting results of the frequency shift and the relative humidity indicated that\nthe measurement error was within Ã?±0.8% RH. When the ethanol concentration ranged from 0 to\n0.2355 g/L, the frequency shift of the sensor was 365 kHz. The effect of the oscillator circuit on the\nadsorption reaction and temperature response of the FBAR sensor device was analyzed to optimize\nits detection application....
Measurement errors of a capacitive voltage transformer (CVT) are relevant to its equivalent\nparameters for which its capacitive divider contributes the most. In daily operation, dielectric aging,\nmoisture, dielectric breakdown, etc., it will exert mixing effects on a capacitive dividerââ?¬â?¢s insulation\ncharacteristics, leading to fluctuation in equivalent parameters which result in the measurement error.\nThis paper proposes an equivalent circuit model to represent a CVT which incorporates insulation\ncharacteristics of a capacitive divider. After software simulation and laboratory experiments,\nthe relationship between measurement errors and insulation parameters is obtained. It indicates\nthat variation of insulation parameters in a CVT will cause a reasonable measurement error. From\nfield tests and calculation, equivalent capacitance mainly affects magnitude error, while dielectric\nloss mainly affects phase error. As capacitance changes 0.2%, magnitude error can reach âË?â??0.2%.\nAs dielectric loss factor changes 0.2%, phase error can reach 5. An increase of equivalent capacitance\nand dielectric loss factor in the high-voltage capacitor will cause a positive real power measurement\nerror. An increase of equivalent capacitance and dielectric loss factor in the low-voltage capacitor\nwill cause a negative real power measurement error....
With Gallium Nitride (GaN) device technology for power electronics applications being\nramped up for volume production, an increasing amount of research is now focused on the\nperformance of GaN power devices in circuits. In this study, an enhancement mode GaN high\nelectron mobility transistor (HEMT) is switched in a clamped inductive switching configuration\nwith the aim of investigating the source of oscillatory effects observed. These arise as a result of\nthe increased switching speed capability of GaN devices compared to their silicon counterparts.\nThe study identifies the two major mechanisms (Miller capacitance charge and parasitic common\nsource inductance) that can lead to ringing behaviour during turn-off and considers the effect of\ntemperature on the latter. Furthermore, the experimental results are backed by SPICE modelling to\nevaluate the contribution of different circuit components to oscillations. The study concludes with\ngood design techniques that can suppress the effects discussed....
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