Wide Range Of Capacitance Research Articles

Multilayer Ceramic Capacitors: An Overview of Failure Mechanisms, Perspectives, and Challenges

Along with the growing of population and social and technological improvements, the use of energy and natural resources has risen over the past few decades. The sustainability of using coal, oil, and natural gas as the main energy sources faces, however, substantial obstacles. Fuel cells, batteries, and super-capacitors have the highest energy densities, but due to their high-power density and rapid charge-discharge speed, regular dielectric capacitors are becoming more popular for pulsed power applications. High electric breakdown strength and high maximum but low-remnant (zero in the case of linear dielectrics) polarization are necessary for high energy density in dielectric capacitors. The high performance, multi-functionality, and high integration of electronic devices are made possible in large part by the multilayer ceramic capacitors (MLCCs). Due to their low cost, compact size, wide capacitance range, low ESL and ESR, and excellent frequency response, MLCCs play a significant role in contemporary electronic devices. From the standpoint of the underlying theories of energy storage in dielectrics, this paper emphasizes the significant problems and recent advancements in building extremely volumetric-efficient MLCCs. Following a thorough examination of the state-of-the-art, important parameters that may be used to improve energy-storage qualities are highlighted, such as controlling local structure, phase assembly, dielectric layer thickness, microstructure, conductivity, different failure modes, and the specific performance during the failure mechanism. The summary of some conclusions on the impending need for innovative materials and diagnostic methods in high-power/energy density capacitor applications appears at the end of the paper.

A modular X-pinch device for versatile X-pinch experiments at Seoul National University.

This paper describes an X-pinch device recently developed at Seoul National University (SNU). The SNU X-pinch device is designed and fabricated to accommodate various diagnostics as well as conduct versatile experiments. It is easy to change the capacitance of the pulse generator because the capacitor bank has a modular design without insulation oil or gas. This allows us to perform a variety of experiments with a wide capacitance range from 80 to 800 nF. The operating voltage of the SNU X-pinch device is controlled from 20 to 100 kV by adjusting the gas pressure inside a triggered spark-gap switch. Triggering of the spark-gap switch is synchronized with the operation of a pulsed laser to diagnose the X-pinch plasma at the proper time. A large vacuum chamber precisely machined from an aluminum mono-block is attached to the top of the pulse generator. It is designed to accommodate not only various X-pinch loads but also various diagnostic apparatus such as optical components. Initial experiments with the SNU X-pinch device have successfully generated x rays with wires of various materials and sizes. The device will be used not only to explore the dynamics of X-pinch plasmas but also as a test stand for diagnostics of high-energy-density plasmas.

Wide Input Dynamic Range Fully Integrated Capacitive Sensor for Life Science Applications.

This paper presents a new fully integrated CMOS capacitance sensor chip with a wider input dynamic range (IDR) compared to the state-of-the-art, suitable for a variety of life science applications. With the novel differential capacitance to current conversion topology, it achieves an IDR of about seven times higher compared to the previous charge based capacitive measurement (CBCM) circuits and about three times higher compared to the CBCM with cascode current mirrors. It also features a calibration circuitry consisting of an array of switched capacitors, interdigitated electrodes (IDEs) realized on the topmost metal layer, a current-controlled 300 MHz oscillator, and a counter-serializer to create digital output. The proposed sensor, fabricated in AMS 0.35μm CMOS technology, enables a high-resolution measurement, equal to 416 aF, of physiochemical changes in the IDE with up to 1.27 pF input offset adjustment range (IOAR). With a measurement speed of 15 μs, this sensor is among the fast CMOS capacitive sensors in the literature. In this paper, we demonstrate its functionality and applicability and present the experimental results for monitoring 2 μL evaporating droplets of chemical solvents. By using samples of solvents with different conductivity and relative permittivity, a wide range of capacitance and resistance variations in the sample-IDE interface electric equivalent model can be created. In addition, the evaporating droplet test has inherently fast dynamic changes. Based on the results, our proposed device addresses the challenge of detecting small capacitance changes despite large parasitic elements caused by the ions in the solution or by remnants deposited on the electrode.

A 45.8 fJ/Step, energy-efficient, differential SAR capacitance-to-digital converter for capacitive pressure sensing

An energy-efficient readout circuit for a capacitive sensor is presented. The capacitive sensor is digitized by a 12-bit energy efficient capacitance-to-digital converter (CDC) that is based on a differential successive-approximation architecture. This CDC meets extremely low power requirements by using an operational transconductance amplifier (OTA) that is based on a current-starved inverter. It uses a charge-redistribution DAC that involves coarse-fine architecture. We split the DAC into a coarse-DAC and a fine-DAC to allow a wide capacitance range in a compact area. It covers a wide range of capacitance of 16.14pF with a 4.5fF absolute resolution. An analog comparator is implemented by cross-coupling two 3-input NAND gates to enable power and area efficient operation. The prototype CDC was fabricated using a standard 180nm CMOS technology. The 12-bit CDC has a measurement time of 42.5μs, and consumes 3.54μW and 0.29μW from analog and digital supplies, respectively. This corresponds to a state-of-the-art figure-of-merit (FoM) of 45.8fJ/conversion-step.

7.9 pJ/Step Energy-Efficient Multi-Slope 13-bit Capacitance-to-Digital Converter

In this brief, an energy-efficient capacitance-to-digital converter (CDC) is presented. The proposed CDC uses digitally controlled coarse-fine multi-slope integration to digitize a wide range of capacitance in short conversion time. Both integration current and frequency are scaled, which leads to significant improvement in the energy efficiency of both analog and digital circuitry. Mathematical analysis for circuit nonidealities, noise, and improvement in energy efficiency is provided. A prototype fabricated in a 0.35-μm CMOS process occupies 0.09 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and consumes a total of 153 μA from 3.3 V supply while achieving 13-bit resolution. The operation of the prototype is experimentally verified using MEMS capacitive pressure sensor. Compared to recently published work, the prototype achieves an excellent energy efficiency of 7.9 pJ/Step.

An integrated energy-efficient capacitive sensor digital interface circuit

In this paper, we propose an energy-efficient 13-bit capacitive sensor interface circuit. The proposed design fully relies on successive approximation algorithm, which eliminates the need for oversampling and digital decimation filtering, and thus low-power consumption is achieved. The proposed architecture employs a charge amplifier stage to achieve parasitic insensitive operation and fine absolute resolution. Moreover, the output code is not affected by offset voltages or charge injection. The successive approximation algorithm is implemented in the capacitance-domain using a coarse-fine programmable capacitor array, which allows digitizing wide capacitance range in compact area. Analysis for the maximum achievable resolution due to mismatch is provided. The proposed design is insensitive to any reference voltage or current which translates to low temperature sensitivity. The operation of a prototype fabricated in a standard CMOS technology is experimentally verified using both on-chip and off-chip capacitive sensors. Compared to similar prior work, the fabricated prototype achieves and excellent energy efficiency of 34pJ/step.

A Wide Tuning Range Voltage Controlled Oscillator Using Common-Base Configuration and Inductive Feedback

Usually the tuning range of voltage controlled oscillator (VCO) is much narrower than the possible resonant frequency range of the tank at different tuning voltages. In this letter we analyze the traditional common-base type VCO, give a simple but useful insight about the mechanism behind the topology, and verified the conclusions with a 2 mum heterojunction bipolar transistor (HBT) VCO. The results show that with the CB configuration, proper feedback inductor and wide tuning range varactor, the tuning range can be almost the same as the resonant frequency range of the tank at different tuning voltages. A wideband voltage controlled oscillator using a commercial 2 mum HBT technology is designed, fabricated and measured. The varactor with wide range of capacitance is used to achieve 53.33% measured tuning range from 9.46 to 16.34 GHz. The measured phase noise at 1 MHz offset is between -90 and -102 dBc/Hz. The total chip size is 1 mm2 including all testing pads, while the core area is 0.64 mm2. The VCO is suitable for wideband application such as in measurement equipment or astronomical exploring telescopes.

Accurate Corona Detector Calibrator

This paper describes an accurate corona detector calibrator for use with test specimens of more than 150 pF. For a wide range of capacitance, built-in calibrators on conventional single-ended corona detectors show errors of two orders of magnitude or more, due to the inductance of their long leads and the single valued calibration coupling capacitors. This portable calibrator is accurate to 10 percent for sample capacitances from 300 pF to above 100 μF. There are three switch-selectable calibration pulse heights. The unit attaches across the test specimen with short leads, and is designed for use with no test voltage present.

Ceramic capacitors for hybrid integrated circuits

Ruggedness, wide capacitance range, high volumetric efficiency, and relatively attractive cost have been the main reasons for the popularity of ceramic chip capacitors. Continuing improvements in most of these categories promise to keep the ceramic chip in its present position of prominence. This article considers multilayer, single-layer, and screened-on configurations. In addition, relationships between size, capacitance, and cost are covered for three common ceramic formulations (NPO, W5R, and Z5U).

INVESTIGATION OF RELAXATION OSCILLATIONS IN THERMISTOR–CAPACITOR SYSTEMS

It is known that a thermistor displays negative resistance at low frequencies when biased with a current greater than turnover current. Thus, when shunted by a capacitance in this condition, sustained oscillations are possible. These oscillations range from a sinusoidal small-amplitude character, when the system is just above threshold for oscillation, to a strongly relaxational type when a large shunt capacitance is employed.The investigation involved a study of the dynamic properties of these oscillations and their relation to the static properties of the thermistor. The relevant thermistor parameters which were measured included the thermal time constant for which special very-low-frequency techniques were developed.The oscillations were studied over a wide range of capacitance covering the transition from sinusoidal to relaxational type. The voltage extrema and period were measured as functions of capacitance, voltage supply resistance, and operating point.An investigation was made of the features of the differential equations describing the behavior of the system, especially for limit cycles corresponding to relaxation oscillations. The asymptotic form of the cycles was derived for the case where the circuital time constant greatly exceeds the thermal time constant of the thermistor. The complicated nature of the equations precluded a solution in a closed form, and approximative methods were found to be necessary. However, in the case of sinusoidal oscillations of small amplitude, the period can be expressed exactly in terms of the system parameters (Burgess 1955b) and this result was confirmed experimentally.

The ignition of explosives by condenser discharges - effect of added circuit resistance

To investigate the mechanism of ignition of explosives by capacitance sparks, the critical ignition energy of lead trinitroresorcinate has been examined for a wide range of capacitance and series resistance.

A Self-Balancing Capacitance Bridge

The combined advantages of the quick indicating capacitance meter and the precision capacitance bridge are obtained in a new form of self-balancing capacitance bridge. Features of the new instrument include per cent deviation indications, a wide capacitance range and an average balancing time of less than two seconds. A single scale, easily read and greatly expanded, serves for the entire range of the instrument and represents an improvement of some 3,000 per cent over conventional capacitance meters. The paper discusses the bridge network development, detector system requirements, and other design considerations.

A capacitance bridge of wide range and a new inductometer

A bridge is described by which quick measurements can be made of capacitances covering a range of from 1μμF up to 30μF, the power factor also being indicated. The unknown capacitance C is put in parallel with a resistance P, and the effective self-inductance of the combination, which is approximately equal to -P2C, is read on a mutual inductometer forming part of the bridge. By giving P a series of suitable values scale multipliers providing for a very wide range of capacitance are obtained. The inductometer used is of a new type, having a circular scale extending to about 260°, the percentage accuracy of reading being almost constant over the greater part of the range. This novel scale system allows the lower readings to be taken with good accuracy. A small rheostat allows the power loss in the condenser to be balanced, and enables the power factor to be deduced.