Showing papers on "Relaxation oscillator published in 2009"

A precision relaxation oscillator with a self-clocked offset-cancellation scheme for implantable biomedical SoCs

Abstract: Recently, there has been an increasing demand for SoCs in the biomedical field [1]. In implantable applications, SoCs are designed under very stringent power and area constraints. The analog and mixed-signal circuits as well as digital circuits in those SoCs require a clock source, because clock-based signal-processing techniques, such as sampling and chopper stabilization, are often used. The primary clock source for such SoCs needs to provide good accuracy and long-term stability of the oscillation frequency ƒ OSC to minimize variations and drifts of the system characteristics. A fairly pure clock signal is required to avoid signal distortion when sampling or chopping techniques are applied. Considering such a source is typically a free-running oscillator, and biomedical signals of typical interest reside at low frequencies, the close-in phase noise is important.

An on-chip CMOS relaxation oscillator with power averaging feedback using a reference proportional to supply voltage

Abstract: Recently, on-chip reference oscillators are required for low-cost single-chip applications including biomedical sensors, microcomputers, high-speed interfaces such as DDR I/F and HDMI (for initial negotiation), and SoCs. RC oscillators (including relaxation oscillators) were developed to realize on-chip oscillators with standard CMOS processes. In this paper, a power-averaging feedback (PAF) concept for accurate oscillators with low power and small area is presented.

Relaxation oscillation profile of limit cycle in predator-prey system

Abstract: It is known that some predator-prey system can possess a unique limit cycle which is globally asymptotically stable. For a prototypical predator-prey system, we show that the solution curve of the limit cycle exhibits temporal patterns of a relaxation oscillator, or a Heaviside function, when certain parameter is small.

Non-isolated current-mode-controlled switching voltage regulator

Abstract: A novel voltage regulator includes an indictor, a switching transistor, a rectifier, an error amplifier circuit, a first voltage comparator circuit, a second voltage comparator circuit, an oscillator circuit, and a driver circuit. The first voltage comparator circuit outputs a modulation signal. The second voltage comparator circuit activates an enable signal when the error voltage exceeds the second reference voltage. The oscillator circuit outputs a clock signal with a fixed frequency according to the enable signal. The oscillator circuit enters a first state when the enable signal is activated and deactivated within a period of time shorter than a threshold time, and enters a second state when the enable signal remains activated during a period of time longer than the threshold time. The driver circuit generates the switching control signal based on the clock signal and the modulation signal.

Hysteretic switching regulator and control method used therein

Abstract: A switching regulator includes a switching transistor, an inductor, a feedback voltage generator, a hysteresis comparator circuit, and a feedback loop circuit. The switching transistor alternately switches on and off. The inductor charges when the switching transistor is on. The feedback voltage generator generates a first feedback voltage by dividing an output voltage. The hysteresis comparator circuit has a voltage comparator to compare the first feedback voltage against a reference voltage to output a comparator output signal as a result of the comparison. The feedback loop circuit feeds the comparator output signal back to the feedback voltage generator to generate a second feedback voltage. The first feedback voltage has an alternating current component substantially dependent on the second feedback voltage varying with the comparator output signal.

Method and circuit for cancelling out comparator-delay in the relaxation oscillator

Abstract: A relaxation oscillator includes a capacitor connected to a comparator input, current sources switched to supply power to the capacitor based on an output of the comparator, and a duplicate integrator shifting a voltage on the capacitor to offset a propagation delay through the comparator. The duplicate integrator includes current sources and a capacitor matching and switched in tandem with those within the relaxation oscillator, plus an additional current source, and is selectively switched into connection with the comparator input. By canceling the comparator propagation delay, the oscillator output frequency can be stably controlled through selection of resistive and capacitive values, using cheaper technology and tolerating large temperature, voltage and process variations.

Experimental results on synchronization times and stable states in locally coupled light-controlled oscillators

Abstract: Recently, a new kind of optically coupled oscillators that behave as relaxation oscillators has been studied experimentally in the case of local coupling. Even though numerical results exist, there are no references about experimental studies concerning the synchronization times with local coupling. In this paper, we study both experimentally and numerically a system of coupled oscillators in different configurations, including local coupling. Synchronization times are quantified as a function of the initial conditions and the coupling strength. For each configuration, the number of stable states is determined varying the different parameters that characterize each oscillator. Experimental results are compared with numerical simulations.

Analytical approximations for the amplitude and period of a relaxation oscillator

Abstract: Analysis and design of complex systems benefit from mathematically tractable models, which are often derived by approximating a nonlinear system with an effective equivalent linear system. Biological oscillators with coupled positive and negative feedback loops, termed hysteresis or relaxation oscillators, are an important class of nonlinear systems and have been the subject of comprehensive computational studies. Analytical approximations have identified criteria for sustained oscillations, but have not linked the observed period and phase to compact formulas involving underlying molecular parameters. We present, to our knowledge, the first analytical expressions for the period and amplitude of a classic model for the animal circadian clock oscillator. These compact expressions are in good agreement with numerical solutions of corresponding continuous ODEs and for stochastic simulations executed at literature parameter values. The formulas are shown to be useful by permitting quick comparisons relative to a negative-feedback represillator oscillator for noise (10× less sensitive to protein decay rates), efficiency (2× more efficient), and dynamic range (30 to 60 decibel increase). The dynamic range is enhanced at its lower end by a new concentration scale defined by the crossing point of the activator and repressor, rather than from a steady-state expression level. Analytical expressions for oscillator dynamics provide a physical understanding for the observations from numerical simulations and suggest additional properties not readily apparent or as yet unexplored. The methods described here may be applied to other nonlinear oscillator designs and biological circuits.

Gated tunnel diode in oscillator applications with high frequency tuning

Abstract: A gated tunnel diode has been introduced into a wave-guide oscillator circuit and the gate is used to tune the oscillation frequency and to turn the oscillator on and off. Oscillators with oscillation frequencies in the range of 9-22 GHz with a typical oscillator output power about -20 dBm have been fabricated. We found that the output power remains essentially constant over a gate bias range (about -260 to 200 mV at V-c = 1.0 V in one oscillator), while it rapidly drops to the noise level over a gate bias range of less than 60 mV above or below the threshold, respectively. In the region with constant power, a total frequency tuning of about 30% is achieved. The maximum oscillation frequency. f(max) (osc), of the gated tunnel diode is set by the tunnel diode and the gate-collector capacitance, and does not depend on the gate-emitter capacitance. This oscillator implementation, in particular, eliminates the need for a separate switch in the realisation of oscillator-based ultra-wide band impulse radios. (C) 2009 Elsevier Ltd. All rights reserved.

Low-power relaxation oscillator

Abstract: The low-power relaxation oscillator comprises a first module ( 21 ) having a ramp generator formed by a reference current source ( 31 ) and a storage capacitor ( 32 ) defining a ramp voltage (V ramp1 ), and a voltage comparator (m 1, m 2 ) for comparing the ramp voltage with a reference voltage, a second module ( 22, 41, 42, V ramp2 , m 3, m 4 ) similar to the first module and an asynchronous flip-flop ( 23 ) receiving the output signal of the comparator of the first module at a first input (s) and the output signal of the comparator of the second module at a second input (r). For each module a generator of said reference voltage is configured by adding a reference resistance ( 33, 43 ) between the reference current source and the storage capacitor. Thus, the generation of the reference voltage and the ramp voltage is conducted on the very same current branch. This enables the electrical power consumption of the oscillator to be reduced.

Precision Threshold Current Measurement for Semiconductor Lasers Based on Relaxation Oscillation Frequency

Abstract: The soft turn-on of semiconductor lasers leads to uncertainty in defining and measuring the laser threshold injection current, I th. Previously, practical calculation algorithms have been developed to achieve high-accuracy measurement of a clearly defined and reproducible quantity which is called I th. We demonstrate a new and higher accuracy measurement of I th using the dependency of the relaxation oscillation frequency on injection current, as compared to the existing standardized approaches. Further, if it is accepted that relaxation oscillations do not occur below laser threshold, this may be regarded as a more fundamentally based definition and measurement method to determine the laser threshold injection current in a semiconductor laser. The method may also be applicable to other types of lasers.

Coherence resonance in a unijunction transistor relaxation oscillator.

Abstract: The phenomenon of coherence resonance is investigated in an unijunction transistor relaxation oscillator and quantified by estimating the normal variance (NV). Depending on the measuring points, two types of NV curves have been obtained. We have observed that the degradations in coherency at higher noise amplitudes in our system is probably the result of direct interference of coherent oscillations and the stochastic perturbation. Degradation of coherency may be minimal if this direct interference of noise and coherent oscillations is eliminated.

Low-voltage low VDD sensitivity relaxation oscillator for passive wireless microsystems

Abstract: A low-voltage relaxation oscillator for passive wireless microsystems is proposed. The oscillator employs a current pulse generator to generate effective hysteresis for oscillation without using a Schmitt trigger, avoiding the drawback of the high sensitivity of the frequency of Schmitt trigger relaxation oscillators to supply voltage fluctuation. The proposed oscillator has been implemented in TSMC-0.18 mum 1.8 V six-metal one-poly CMOS technology. The performance of the oscillator is validated using measurement results.

Sinusoidal oscillators and multivibrators are not separate classes of circuits

Abstract: When multivibrators are forced to operate at high frequencies one usually observes transition from relaxation to sinusoidal oscillations. One considers that at these frequencies the parasitic capacitors of active devices become comparable with functional capacitors, and the effect of parasitic produces this “smoothing” of oscillations. This paper considers a counterintuitive example: the oscillator where the transition goes in opposite direction. The operation starts from sinusoidal oscillations at low frequencies. Reducing the functional capacitor value one obtains relaxation oscillations at higher frequencies. This example shows that oscillators and multivibrators are not separate classes of circuits.

A temperature-compensated circuit and method thereof

Abstract: The present invention discloses a temperature-compensated circuit and method thereof. Disclosed are various embodiments of temperature-compensated relaxation oscillator circuits that may be fabricated using conventional CMOS manufacturing techniques. The relaxation oscillator circuits described herein exhibit superior low temperature coefficient performance characteristics, and do not require the use of expensive off-chip high precision resistors to effect temperature compensation. Positive and negative temperature coefficient resistors arranged in a resistor array offset one another to provide temperature compensation in the relaxation oscillator circuit.

Sine Wave Oscillators

Abstract: Publisher Summary This chapter discusses the sine wave oscillators that are intentionally designed unstable circuit. They are useful for creating uniform signals that are used as a reference in applications such as audio, function generators, digital systems, and communication systems. Two general classes of oscillators exist: sinusoidal and relaxation. Sinusoidal oscillators consist of amplifiers with RC (resistance/capitance) or LC (inductance/capitance) circuits that have adjustable oscillation frequencies or crystals that have a fixed oscillation frequency. Op amp sine wave oscillators operate without an externally applied input signal. Some combination of positive and negative feedback is used to drive the op amp into an unstable state, causing the output to transition back and forth at a continuous rate. The amplitude and the oscillation frequency are set by the arrangement of passive and active components around a central op amp. Op amp oscillators are restricted to the lower end of the frequency spectrum because op amps do not have the required bandwidth to achieve low phase shift at high frequencies. Voltage feedback op amps are limited to the low kilohertz range, since their dominant, open loop pole may be as low as 10 Hz. The new current feedback op amps have a much wider bandwidth, but they are very hard to use in oscillator circuits, because they are sensitive to feedback capacitance.

Gate-controlled diode - a new way for electronic circuits

Abstract: The paper presents new applications for the gate-controlled diode working in the breakdown regime. The proposed circuits are based on the special transfer characteristic having linear portions and switching with hysteresis features. Two examples are given, namely the follower amplifier and the relaxation oscillator.

Power supply and dc-dc-conversion

Abstract: In an embodiment of a converter, a first oscillator provides switching signals for switching between charging and discharging of a capacitor, and a second oscillator is configured to add an offset voltage or a feedback-current-dependent voltage to a sawtooth waveform generated by the second oscillator switched in synchronism with the first oscillator.

Relaxation oscillator for compensating system delay

Abstract: A relaxation oscillator compensates for system delay. The relaxation oscillator includes first and second input signal units that generates first and second capacitor voltages, a delay compensation unit that receives a reference voltage and the first and second capacitor voltages and that generates a compensation voltage. In certain embodiments, a voltage generating unit applies the reference voltage to the delay compensation unit, and a latch unit stores first and second comparison signals compared by the first and second input signal units and transmits a clock signal and a inverted clock signal to the first and second input signal units. The first and second input signal units compare the first and second capacitor voltages with a compensation voltage transmitted from the delay compensation unit.

Low-noise voltage controlled oscillator

Abstract: A low-noise voltage controlled oscillator is provided, to improve a phase noise characteristic and widen a frequency variable range. The low-noise voltage controlled oscillator is configured so that an oscillation element and a capacitor 2 are connected in series between a collector C and an emitter E of a transistor 1, capacitors 3 and 4 are connected in series between the collector C and the emitter E, an electrical potential between the capacitors 3 and 4 is applied to a base B of the transistor 1; a one-port circuit 6 is provided between the collector C and the capacitor 4; and a capacitor for correction 5 is connected in parallel with the capacitors 3 and 4. The one-port circuit 6 includes a tuned circuit provided with a variable capacitor adjusting a capacity thereof smaller and an inductor adjusting a value of inductance larger so as to set a value of impedance relatively large.

Fault tolerant redundant clock circuit

Abstract: A clock generation circuit, includes, in part, a comparator, a logic unit, and a switching circuit. The switching circuit generates a signal that is applied to the comparator. If the input voltage level of the signal applied to the comparator is greater than a first reference voltage, the comparator asserts its first output signals. If the input voltage level of the signal applied to the comparator is less than a second reference voltage, the comparator asserts its second output signal. The output signals of the comparator form a first pair of feedback signals applied to the switching circuit. The logic unit responds to the output signals of the comparator to generate a second pair of oscillating feedback signals that are also applied to the switching circuit. The switching circuit varies a capacitor voltage in response to a reference current and in response to the two pairs of feedback signals it receives.

Low-power relaxation oscillator and RFID tag using the same

Abstract: There is provided a low-power relaxation oscillator. The low-power relaxation oscillator may include: a constant current generation unit generating a current having a predetermined magnitude; a current varying unit controlling the current generated from the constant current generation unit according to a clock control signal to output the controlled current; a first controller and a second controller connected in parallel with output terminals of the current varying unit and passing or interrupting the current supplied from the current varying unit; a PMOS charging/discharging unit arranged between an output terminal of the first controller and an output terminal of the second controller; a first comparator and a second comparator connected to both ends of the PMOS charging/discharging unit, respectively, and each outputting a high or low level voltage upon receiving voltage charged in the PMOS charging/discharging unit; and a latch circuit delaying the voltages output from the first and second comparators to output oscillation signals.

X-band Voltage Controlled Oscillator using Varactor Diode

Abstract: In this paper, a X band voltage controlled oscillator is proposed. The oscillator uses a transistor as an oscillating element and its oscillating frequencies are controlled by the tuning voltage of varactor diode. Using the circuit simulation tools, the matching circuits between the transistor and varactor diode, its input and output matching circuits, and a feedback circuits are designed. The measured results of the fabricated oscillator show that its oscillation frequencies are from 10.50GHz to 10.88GHz according to the turning voltages of 1V to 18V, its output power levels are about 4.3dBm, and its phase noise is around -43.5dBc/Hz at 100kHz offset frequency of 10.5GHz.

Relaxation oscillator using spintronic device

Abstract: Disclosed herein is a relaxation oscillator using a spintronic device. The relaxation oscillator includes a power source unit, a spintronic device, and a capacitor. The power source unit applies power. The spintronic device is driven by the power applied by the power source unit, and has a variable voltage value depending on the intensity of a magnetic field. The capacitor is connected in parallel with the spintronic device, and is discharged when it assumes a minimum-voltage value in the threshold voltage range of the spintronic device and charged when it assumes a maximum voltage value in the threshold voltage range.

A Synthetic Biology Approach to Understanding Biological Oscillations: Developing a Genetic Oscillator for Escherichia coli

Abstract: Our goals are to construct a simple genetic clock that will stably oscillate in Escherichia coli and to identify the design principles and parameters responsible for oscillations. We previously described a simple genetic circuit of linked activator and repressor operons that produced damped oscillations. Here, we altered the repression of the activator operon and identified an oscillator that produces improved oscillations over our initial system. We also explored mathematical models of the oscillator. Toy models were used to investigate the behaviors that may be obtained from our clock circuitry. Depending on parameters, the circuitry produced a wide array of oscillatory systems, including sinusoidal and relaxation oscillators. We also attempted to explicitly model all known interactions that affect the oscillator, producing a 32-dimensional ODE model. This model can produce results similar to those obtained in experiments, and we have begun attempts to fit experimental data to the model.

Buck type auxiliary electric power controlled by PFM

Abstract: The present invention discloses a buck auxiliary power supply controlled by PFM, which comprises a Buck conversion main circuit connected with input voltage +VIN, characterized in that control input end of the Buck conversion main circuit connects with a PFM control circuit, the PFM control circuit comprises a relaxation oscillator composed by a operational amplifier, and the output impulse controls conducting and switch off of the main switch tube of Buck conversion main circuit and allows Buck conversion main circuit output auxiliary power supply pressure VCC; the auxiliary power supply pressure VCC passes through a feedback circuit to connect with the relaxation oscillator; when the auxiliary power supply pressure higher than preset output pressure, the feedback circuit makes relaxation oscillator output impulse dutyfactor descend, and controls the Buck conversion main circuit output pressure reduce; when the auxiliary power supply pressure lower than the preset output pressure, the feedback circuit makes relaxation oscillator output impulse dutyfactor increase, and controls the Buck conversion main circuit output pressure raise so as to keep the auxiliary power supply output pressure stable.

Relaxation Oscillation in GST-Based Phase Change Memory Devices

Abstract: The purpose of this work is to investigate the material and device properties of GST-based PCM by studying relaxation oscillations [1, 2]. Our experimental results relate oscillation characteristics to applied voltage, load resistance and device thickness.