Search

This paper presents a simple, novel interfacing scheme for linear variable differential transformer (LVDT) that does not require a precise sine wave oscillator (with stable amplitude and frequency) for excitation or any phase matching circuit like traditional methods. The primary and the secondary coils of the LVDT are integral parts of a relaxation oscillator (RO). The RO injects a current waveform with a triangular shape through the primary coil which in turn induces a square-shaped voltage waveform in the secondary coils. The RO utilizes the amplitudes of those waveforms and generates a pulsewidth modulation (PWM) output signal whose duty cycle ratio is proportional to the measurand, core position. This quasi-digital PWM signal is passed through a low-pass filter to obtain an analog output. PWM time period measurement using a counter yields a digital output. This method guarantees good stability since the output is dependent only on a pair of dc reference voltages apart from the transformation constant of the sensor. A detailed analysis of the sources of error, their effect on the performance of the scheme and appropriate design choices for error mitigation are also presented. A prototype of the proposed circuit was built and tested in the laboratory. The nonlinearity error noted from the tests conducted was less than 0.16% for the analog output and 0.18% for the digital output. A resolution of up to 11 bits was achieved for the digital output. [ABSTRACT FROM AUTHOR]

In this paper, a pW-power relaxation oscillator for sensor node applications is presented. The proposed oscillator operates over a wide supply voltage range from nominal down to deep sub-threshold and requires only a sub-pF capacitor for Hz-range output frequency. A true pW-power operation is enabled thanks to the adoption of an architecture leveraging transistor operation in super-cutoff, the elimination of voltage regulation, and current reference. Indeed, the oscillator can be powered directly from highly variable voltage sources (e.g., harvesters and batteries over their whole charge/discharge cycle). This is achieved thanks to the wide supply voltage range, the low voltage sensitivity of the output frequency and the current drawn from the supply. A test chip of the proposed oscillator in 180 nm exhibits a nominal frequency of approximately 4 Hz, a supply voltage range from 1.8 V down to 0.3 V with 10%/V supply sensitivity, 8–18-pA current absorption, and 4%/°C thermal drift from -20 °C to 40 °C at an area of $1600~\mu \mathrm {m}^{2}$. To the best of the authors’ knowledge, the proposed oscillator is the only one able to operate from sub-threshold to nominal voltage. [ABSTRACT FROM AUTHOR]

This study investigates the temperature dependence of current-controlled negative differential resistance (CC-NDR) in Pt/NbOx/TiN devices and its effect on the dynamics of associated Pearson-Anson relaxation oscillators. The voltage range over which CC-NDR is observed decreases with increasing temperature such that no NDR is observed for temperatures above ~380K. Up to this temperature, relaxation oscillators exhibit voltage and temperature dependent oscillation frequencies in the range of 1 to 13MHz. Significantly, the sensitivity of the frequency to temperature changes was found to be voltage-dependent, ranging from 39.6 kHz/K at a source voltage of 2V to 110 kHz/K at a source voltage of 3V, in the temperature range of 296–328K. Such a behaviour provides insights into temperature tolerance and tuning variability for environmentally sensitive neuromorphic computing. [ABSTRACT FROM AUTHOR]

A complementary metal oxide semiconductor relaxation oscillator adopting a new frequency self-calibration technique (FSCT) to improve the linearity is proposed in this paper. The FSCT can detect the peak voltage of the timing capacitor when start-up and change the reference voltage adaptively. Then, the non-linearity of the oscillator caused by the delay of the control circuit and the offset voltage of the comparator can be reduced obviously. The proposed relaxation oscillator with typical frequency of 5 MHz is implemented in 0.5 μm Silicon-On-Insulator Bipolar-CMOS-DMOS process. Measured results show that <0.79% non-linearity in the current-frequency transfer function from 0.1 to 10 MHz without trimming. [ABSTRACT FROM AUTHOR]

This paper presents a new compact CMOS capacitance multiplier. The multiplier is based on using the translinear principle with MOSFETs operating in subthreshold region. The multiplication factor is controllable to meet the designer requirements. Tanner TSPICE simulator was used to confirm the functionality of the design in 0.18 µm CMOS Technology. The circuit operates from ±0.75 supply voltage. Simulation results indicate that the multiplication factor can be varied from 10 to 300. The functionality of the proposed capacitance multiplier was demonstrated by using it in designing a low pass filter and a relaxation oscillator. [ABSTRACT FROM AUTHOR]

In this paper, the effects that limit the performance of practical implementations of RC relaxation oscillators are investigated. The insights gained are used to suggest a topology for high-frequency quadrature relaxation oscillators with closer-to-optimal performance. The proposed oscillator uses a modified latch to improve the switching speed without increasing the power consumption. Moreover, the new topology avoids static current sources, maximizes the voltage swing and has an active coupling structure without static power consumption that reduces the circuit phase-noise. Experimental results show that the oscillator operates in relaxation mode at 2.4 GHz and achieves a FoM of $$\mathrm {-162\,dBc/Hz}$$ , which is, as far as the authors know, the best FoM for relaxation oscillators operating in the GHz range. [ABSTRACT FROM AUTHOR]

A relaxation oscillator using a memristor is hereby presented. The memristor is used to substitute the function of a capacitor in an equivalent RC oscillator. The voltage across the memristor changes according to the quantity and polarity of the current passing through, thus substituting the changing voltage across a capacitor in the equivalent RC oscillator. The memristor has the advantage of occupying much less area than the equivalent capacitor, which may be important when trying to build on-chip oscillators for portable or medical applications. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper discusses the boundary dynamics of the charge-controlled memcapacitor for Joglekar's window function that describes the nonlinearities of the memcapacitor's boundaries. A closed form solution for the memcapacitance is introduced for general doping factor $$p$$ . The derived formulas are used to predict the behavior of the memcapacitor under different voltage excitation sources showing a great matching with the circuit simulations. The effect of the doping factor $$ p$$ on the time domain response of the memcapacitor has been studied as compared to the linear model using the proposed formulas. Moreover, the generalized fundamentals such as the saturation time of the memcapacitor are introduced, which play an important role in many control applications. Then the boundary dynamics under sinusoidal excitation are used as a basis to analyze any periodic signal by Fourier series, and the results have been verified using PSPICE simulations showing a great matching. As an application, two configuration of resistive-less memcapacitor-based relaxation oscillators are proposed and closed form expressions for oscillation frequency and conditions for oscillation are derived in presence of nonlinear model. The proposed oscillator is verified using PSPICE simulation showing a perfect matching. [ABSTRACT FROM AUTHOR]

The memristor is a new-found circuit element and its applications in programmable circuits are also under study. Analysis of most of its combinations with other circuit elements such as resistors, capacitors, and inductors does not exist. In this work, a TiO2 memristor model with linear dopant drift speed is used and the solution of a TiO2 memristor and capacitor series circuit driven by a constant voltage source is given. It is then used to analyze a novel M-C oscillator circuit. In previous programmable oscillator studies, the memristance of the oscillator was assumed to be constant. However, in this study, the analysis of the M-C oscillator is done considering time-varying memristance and using the solution of the TiO2 memristor and capacitor series circuit supplied by a constant voltage. In this work, a formula for calculation of the exact value of the M-C oscillator frequency is given. Minimum and maximum operation frequencies of the oscillator are also calculated. [ABSTRACT FROM AUTHOR]

SUMMARY This paper introduces two voltage-controlled memristor-based reactance-less oscillators with analytical and circuit simulations. Two different topologies which are R-M and M-R are discussed as a function of the reference voltage where the generalized formulas of the oscillation frequency and conditions for oscillation for each topology are derived. The effect of the reference voltage on the circuit performance is studied and validated through different examples using PSpice simulations. A memristor-based voltage-controlled oscillator (VCO) is introduced as an application for the proposed circuits which is nano-size and more efficient compared to the conventional VCOs. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A relaxation oscillator with integrated voltage and current reference generation circuitry is presented in this paper for on-chip clock signal generation in low-power applications. Designed and simulated in 0.11 μm CMOS technology, the oscillator provides a clock signal at the frequency of 20 kHz with a temperature coefficient of 314 ppm/ °C over a range from −20 to 80 °C. The oscillator's output signal frequency has a standard deviation of 7.9 % under the influence of device mismatches. It operates with a supply voltage of 1.2 V and has a dynamic power consumption of 4.9 μW at room temperature. An integrated voltage and current reference generator was developed to provide two reference voltages at 484.6 and 663.5 mV with simulated temperature coefficients of 7.5 and 16 ppm/ °C over a range from −20 to 80 °C respectively, as well as a reference current of 26.84 nA with a temperature coefficient of 166 ppm/ °C over the same temperature range. [ABSTRACT FROM AUTHOR]

An accurate self-adjusting CMOS RC oscillator for capacitive and resistive sensor applications has been designed and manufactured. The oscillator operates with supply voltages from 1.2 to 3 V and achieves an internal accuracy of ±9.7% with a temperature range from -20 °C to 60 °C. The RC oscillator was fabricated in a 0.35-µm standard n-well CMOS process with threshold voltages of 0.5 and -0.65 V. Its design and operation are described, and results of measurements performed on the fabricated chips are presented. [ABSTRACT FROM AUTHOR]

This paper presents a capacitive angular-position sensor with a contactless electrically floating conductive rotor and an interface electronic circuit that is designed to maximize the performance/cost ratio. The sensor includes two separate and independent measurement sections that sense the same angle and provide redundancy in critical applications. The electronic interface is based on a relaxation oscillator that, for each of the two sections, measures an appropriate quantity that relates capacitance ratio to angular position and provides a dc output voltage that varies ratiometrically with respect to the supply voltage. The sensor was built in a version with ±11° measuring range for each section. Experimental tests showed a linearity better that 1% of the span. [ABSTRACT FROM AUTHOR]

An on-chip 23 kHz dual-phase relaxation oscillator is presented. Charge-transfer and comparator offset cancellation techniques have been proposed to achieve low power and high temperature stability. The circuit has been designed with 0.18 µm CMOS process. The oscillator has achieved an ultra-low power of 130 nW, a supply voltage sensitivity of 0.8%/V over 1.2-1.8 V, and a temperature coefficient of 30 ppm/°C over -40 to 80°C. [ABSTRACT FROM AUTHOR]