Showing papers on "Relaxation oscillator published in 2000"

Phase equations for relaxation oscillators

Abstract: We use the Malkin theorem to derive phase equations for networks of weakly connected relaxation oscillators. We find an explicit formula for the connection functions when the oscillators have one-dimensional slow variables. The functions are discontinuous in the relaxation limit $\mu \rightarrow 0$, which provides a simple alternative illustration to the major conclusion of the fast threshold modulation (FTM) theory by Somers and Kopell [Biological Cybernetics, 68 (1993), pp. 393--407] that synchronization of relaxation oscillators has properties that are quite different from those of smooth (nonrelaxation) oscillators. We use Bonhoeffer--Van Der Pol relaxation oscillators to illustrate the theory numerically.

Calibration techniques for a precision relaxation oscillator integrated circuit with temperature compensation

Abstract: Several calibration techniques for a precision relaxation oscillator with temperature compensation produces a stable clock frequency over wide variations of ambient temperature. The calibration techniques provide for different methods of determining CTAT current, PTAT current or the ratio of PTAT current to CTAT current. The calibration techniques provide different methods for determining CTAT and PTAT calibration values and for setting CTAT and PTAT calibration select switches.

Low supply voltage relaxation oscillator having current mirror transistors supply for capacitors

Abstract: Presented is a low supply voltage oscillator circuit having at least one capacitor to be controlled, connected between first and second voltage references, and a circuit for charging and discharging the capacitor to be controlled. The oscillator circuit also includes at least first and second stages having symmetrical structures in a mirror-image configuration and being connected between the first voltage reference and the second voltage reference and connected together through a memory element. The oscillator circuit also includes respective primary switches for alternately charging the capacitors in a controlled fashion.

Stochastic relaxation oscillator model for the solar cycle.

Abstract: We perform a detailed analysis of the sunspot number time series to reconstruct the phase space of the underlying dynamical system. The features of this phase space allow us to describe the behavior of the solar cycle in terms of a simple relaxation oscillator in two dimensions. The absence of systematic self-crossings suggests that the complexity of the sunspot time series does not arise as a consequence of chaos. Instead, we show that it can be adequately modeled through the introduction of a stochastic fluctuation in one of the parameters of the dynamic equations.

Oscillator-based interface for measurand-plus-temperature readout from resistive bridge sensors

Abstract: A signal conditioning circuit based on a relaxation oscillator is proposed for use with resistive bridge sensors. The circuit provides a rectangular-wave output whose frequency is related to the bridge unbalance, and duty-cycle is a function of the overall sensor bridge resistance, hence of the sensor operating temperature. In this way, two measurement values are simultaneously and independently carried on the same output signal. The circuit makes use of a constant current bridge excitation which enables the connection of remote sensors without accuracy degradation, and moreover, for silicon piezoresistive sensors, provides a first-order temperature compensation. A frequency-doubling output stage significantly reduces the nonlinearity due to switching delay times, at the parity of output center frequency and span. Experimental results are reported on the characterization of both the circuit alone and interfaced to a silicon pressure sensor.

Limitations of a relaxation oscillator in capacitance measurements

Abstract: Oscillation periods of a relaxation oscillator consisting of an op-amp-based integrator and a comparator are measured over a wide range of RC integration constants, and the results are compared with theoretical values derived in terms of the finite gain-bandwidth (GB) product and the slew rate of an op-amp and the response delay of a comparator The comparison validates the theoretical derivation which gives the design criteria of a relaxation oscillator for capacitance measurements and sensor signal processing

A simple pulse width modulator using current conveyor

Abstract: A simple pulse width modulator (PWM) is proposed. The circuit principle is based on a relaxation oscillator with a second generation current conveyor (CCII). The proposed scheme is simpler than the existing PWM methods and the duty factor linearly depends on the modulating signal. Another advantage is that the circuit is suitable for IC implementation. The simulation and experimental results are given. They show good agreement with the theoretical analysis.

Inductive proximity sensor oscillator

Abstract: An inductive proximity sensor oscillator (A) having a differential comparator (38) in combination with a negative feedback network (38) and a positive feedback network connected to the comparator. The positive feedback network (22, 36) determines the frequency and amplitude of the generated oscillations. An LC resonant tank circuit (22) is connected between a non-inverting input (30) and a fixed reference voltage (20), and a current limiting resistor (36) connected between the non-inverting input and the output of the comparator. The negative feedback network (38) provides a simple, fast and reliable start-up mechanism. It comprises a capacitor (40) connected between the inverting input of the comparator and the circuit ground and a resistor (42)

Low-voltage relaxation oscillator

Abstract: A relaxation oscillator employing an S-shaped current-controlled nonlinear resistor composed of two bipolar transistors and a single resistor is proposed. The oscillator produces a unipolar sawtooth waveform and is suitable for low-voltage applications.

Robustness of a relaxation oscillator

Abstract: For a relaxation oscillator which consists of a relay-hysteresis in feedback with negative integral action we prove that the oscillatory behaviour is robust to perturbations in the dynamical component of the feedback loop which are sufficiently small in a gap sense.

Emergent mechanisms in multiple pattern generation of the lobster pyloric network.

Abstract: By using a hard-wired oscillator network, multiple pattern generation of the lobster pyloric network is simulated. The network model is constructed using a relaxation oscillator representing an oscillatory or quiescent (i.e. steady-state) neuron. Modulatory inputs to the network are hypothesized to cause changes in the dynamical properties of each pyloric neuron: the oscillatory frequency, the postinhibitory rebound property, and the resting membrane potential. Changes in each of these properties are induced by changing appropriate parameters of the oscillator. By changing seven parameters of the network as a whole, modulatory input-dependent patterns are successfully simulated.

Resonant-tunneling-diode relaxation oscillator☆

Abstract: Monolithic resonant-tunneling-diode (RTD) relaxation oscillators are fabricated. The highest repetition rate of this pulse generator is 6.7 GHz with a pulse width of approximately 60 ps. Oscillators with an RTD connected to an off-chip transmission line have been operated at a rate as low as 34 MHz while maintaining a similar pulse width. Characterization aided with simulations provides a better understanding of the RTD relaxation oscillator and the effects of the RTD characteristics on the performance of the oscillator.

Stable oscillations and Devil's staircase in the van der pol oscillator

Abstract: A forced van der Pol relaxation oscillator is studied experimentally in the regime of stable oscillations. The variable parameter is chosen to be the driving frequency. For a range of parameter values, we show that the rotation number varies continuously from 0 to 1. This work provides experimental evidence that period-adding bifurcations to chaos previously reported by Kennedy and Chua are intimately connected to the existence of a regime of stable oscillations where the rotation number shows a Devil's-staircase structure.

Voltage controlled oscillator assembly

Abstract: Voltage controlled oscillator assembly comprising means for detecting a control voltage input and means for generating an output frequency signal depending on said control voltage input. Said voltage controlled oscillator assembly comprises at least two voltage controlled oscillators, means for reading data from an external source, and means for individually switching the at least two voltage controlled oscillators on and off in accordance with the data read.

Robustness of a relaxation oscillator

Abstract: For a relaxation oscillator which consists of a relay-hysteresis in feedback with negative integral action we prove that the oscillatory behaviour is robust to perturbations in the dynamical component of the feedback loop which are sufficiently small in a gap sense.

Ring VCO based on RC timing

Abstract: The present invention, generally speaking, provides a controlled oscillator that attains the foregoing objectives The structure of the oscillator is, in general, that of a ring; however, timing of the oscillator is governed largely by an RC time constant Since the delay is mostly RC-based, phase noise is minimal compared to an active implementation Furthermore, in a preferred embodiment, two ring oscillators of this type are combined to form a differential oscillator circuit having still lower phase noise In an exemplary embodiment, the ring oscillators are three-stage ring oscillators The operation of two inverters is unaffected by the RC time constant Because the speed of these inverters is very fast compared to the RC time constant, the oscillation frequency is quite constant versus temperature and supply voltage

A novel technique to measure two independent components of impedance sensors with a simple relaxation oscillator

Abstract: A simple interface circuit for impedance measurement based on a relaxation oscillator is presented. The measurement strategy is revealed and the principle of operation is discussed. It is intended for measuring impedance, which can be presented with a capacitor and resistor in series. By means of a four-signal measurement technique a continuous self-calibration is achieved. The output signals for both components of the unknown impedance are time-periods and for calculating their values only one reference capacitor is needed. A measurement setup is presented with which the new method was tested. The experimental results prove that with this new technique very high sensitivity for both components of the measured impedance can be achieved.

Integrator/ comparator control of ring oscillator frequency and duty cycle

Abstract: A control circuit for a ring oscillator uses an integrator and a comparator. The integrator receives a square wave signal as an input and provides a triangular wave signal as an output. The comparator generates a second square wave signal by comparing the triangular wave signal and a reference voltage. Duty cycle for the ring oscillator can be modulated by varying the reference voltage. For one embodiment of the control circuit, signal frequency of the ring oscillator can be modulated by varying biasing current for the comparator to set slew rate of the comparator. For one embodiment of the control circuit, a resistor and a capacitor form a simple RC circuit for the integrator. For an alternative embodiment of the control circuit, a resistor and an amplifier with a capacitor in a negative feedback loop form an active RC circuit for the integrator. For one embodiment of the control circuit, the comparator is an inverting comparator. A ring oscillator employing the control circuit can be formed using a plurality of inverters coupled in series with the control circuit. A test system can be formed by coupling an output buffer and the ring oscillator to a device-under-test and monitoring the ring oscillator frequency and device characteristics.

Temperature compensation of an integrated low power inductive proximity microsensor

Abstract: A simple temperature compensation method for inductive proximity microsensors based on the differential relaxation oscillator has been developed and successfully tested. With this compensation and for the temperature range from −20°C to +80°C, an accuracy better than ±10 μm at 1 mm distance to an aluminum target has been measured. The microsensor has been integrated with a 3-V, 1-μm CMOS read-out circuit using a gold bumping layer to form a 3.8-mm side flat coil. The power consumption of the whole compensated microsystem is lower than 10 mW. To achieve this, the temperature behaviors of the whole microsensor and of its building elements, namely the sensing coil (nearby a target) and the read-out circuit, have been studied and a compensation method has been developed. The inductance of the integrated coil is temperature-independent in the frequency range up to 12 MHz, whereas its resistance depends mainly on the temperature coefficient of the conductor resistivity. The resonance frequency of the coil is not affected by temperature. In its principle, the electronic circuit has a temperature-dependent drift in the sensing distance range. This drift can, however, be compensated using a negative temperature coefficient resistor. Analytical derivations and simulation tools have been used for the choice of the optimal coefficient for a specific sensing distance range.

Method and apparatus for a gated oscillator in digital circuits

Abstract: A gated oscillator is provided for digital circuits. The gated oscillator is achieved by the unconventional use of controlling the operating point of a Van der Pol oscillator. Oscillations are achieved by Van der Pol self-oscillation behavior. The result is a highly simplified gated oscillator circuit for many digital circuit applications

Power voltage reduction compensating circuit for oscillator

Abstract: PROBLEM TO BE SOLVED: To provide a power voltage reduction compensating circuit capable of maintaining the operation of an oscillator with a sufficient margin even when a battery voltage is lowered. SOLUTION: In this circuit, a switch 3 is inserted in series between a power source terminal Vcc of an oscillator 1 and a positive voltage terminal (+) of a battery 2, a resistor R1, a capacitor C1 and the serial connection of the cathode of a diode D1 and the anode of a diode D2 are inserted in parallel between a negative voltage terminal (-) of the battery 2 and a ground terminal GND of the oscillator 1, further a hybrid transformer 4 is inserted between the output of the oscillator 1 and a signal output terminal and the branch output of the hybrid transformer 4 is connected through a capacitor C2 to the node of the cathode of the diode D1 and the anode of the diode D2. Besides, a circuit composed of the resistor R1, the capacitors C1 and C2 and the diodes D1 and D2 is a negative voltage generating circuit 5.

Noise in CMOS Voltage Controlled Relaxation Oscillators

Abstract: A low-noise voltage controlled relaxation oscillator (VCO) has been fabricated in a 2 micron CMOS process. The VCO uses a grounded external timing capacitor and a bypassed latch. A theoretical analysis is presented showing that the VCOs output phase noise is dominated by the undersampling of circuit noise arising principally from the comparators. A minor correction to equation (21) of Abidi and Meyer in [1] is also derived. The VCO design was modified to allow a comparison between two different comparator architectures whilst sharing a common VCO core of current sources, timing capacitor and latch. Spectrum analyzer measurements are presented which confirm the theoretical predictions and show that high frequency signals are aliassed down to appear as noise sidebands about the carrier frequency. The oscillator’s phase noise was measured as −70 dBc/Hz at a 20 kHz offset when oscillating at 1.1 MHz.

Nonlinear transport phenomena and mode locking in millimetre-wave Gunn-instability structures

Abstract: The nonlinear behaviour of drift-diffusion transport model of the 3 µm GaAs Gunn-effect structure is analysed here. It is shown that the correct choice of the v(E) form and its exact approximation is necessary. Increase of the v(E) dependence steepness in the region above the threshold leads to dissolution of the dipole domains before anode contact. A local extremum appears on the dependence of the transit frequency on the applied dc voltage. This complicates mode-locking processes when a driving microwave signal is applied. The effective length of the transit region quasiperiodically changes, similarly to threshold modulation in relaxation oscillator models. The nonlinear interaction of oscillations leads to multiplication of the current oscillations period and complication of the terminal current shape. The quasiperiodic microwave signal outside the phase-locking regions has different upper and lower envelopes, leading to the appearance of an additional high-frequency component in the signal spectrum. T...

Phase locked loop circuit for semiconductor integrated circuit, has selector which selects voltage controlled oscillation circuit of optimum oscillation frequency band from several oscillation circuits in oscillator

Abstract: A low pass filter (2) outputs control voltage signal (S2) based on the phase difference signals (S1) output from phase comparator (1). An oscillator (3) changes the oscillation frequency of each oscillator circuit (4) in it according to the control voltage signal. A selector (5) selects an oscillation circuit (4) of optimum oscillation frequency band from several oscillation circuits in oscillator. A phase comparator (1) compares the phase difference between external clock signal (CK1) and internal clock signal (CK2) and outputs a phase difference signal (S1). A low pass filter outputs control voltage (S2) based on phase difference signal. A voltage controlled oscillators circuit e.g. ring oscillator has several converters which are serially connected to frequency variable invertors to control frequency. Independent claim are also included for the following: (a) semiconductor integrated circuit; (b) voltage controlled oscillator

Averaging method via all numerical computation applied to weakly-nonlinear coupled oscillator systems

Abstract: This paper proposes a totally-numerical method of averaging without derivation of the averaged equation. To check this method, we apply this algorithm to three and four asymmetrical coupled van der Pol oscillator systems which have been analyzed by conventional method of averaging in our previous paper. Comparing these two results, we have confirmed the validity of this method. The final purpose for which we develop this numerical algorithm is to analyze a large scale coupled oscillator systems via the averaging method in the near future.

Tracking Rhythms with a Relaxation Oscillator

Abstract: A number of biological and mechanical processes are typified by a continued slow accrual and fast release of energy. A nonlinear oscillator exhibiting this slow-fast behavior is called a relaxation oscillator and is used to model, for example, human heartbeat pacemaking (van der Pol & van der Mark, 1928) and neural action potential (Hodgkin & Huxley 1952; Fitzhugh 1961; Nagumo, 1962). Similar limit cycle oscillators are used to model a wider range of behaviors including predator-prey relationships and synchrony in animal populations such as fireflies. See Winfree (1980) for a review. Though nonlinear limit-cycle oscillators have been successfully applied to beat induction (Large & Jones, 1999; Large & Kolen, 1994; McAuley, 1995; Gasser, Eck, & Port 1999) relaxation oscillators have received less attention. In this work we offer a novel and effective relaxation oscillator model of beat induction. We outline the model in detail and provide a perturbation analysis of its response to external stimuli. In a series of simulations we expose the model to patterns from Experiment 1 of Povel & Essens (1985). We then compare the beat assignments of the model to those made by the Povel & Essens (1985) matching model. Although the overall performance of the model is very good, there are shortcomings. We believe that a network of mutually-coupled oscillators will address many of these shortcomings, and we suggest an appropriate course for future research.

Oscillation circuit with wide dynamic range

Abstract: The oscillator circuit (1) comprises a voltage controlled oscillator (2) regulated by a voltage provided at a first input (3) by a control device (5). The control is supplied by a first voltage source, and produces the control voltage. The oscillator has a second input connected to a switching circuit (34) which is located between the first voltage source and a second voltage source. The output of the switching circuit is fed via a low pass filter (39) to the oscillator node (32). The switching circuit comprises two transistors (40,41) with the emitters connected to the first and second supply potentials, respectively, and the collectors connected to the output (38) of the switching circuit, so that the transistors (40,41) are controlled in complement mode by two control circuits (42,44) and control signals directed to the bases of transistors. This allows the oscillator to be supplied with two different potential values for augmenting the dynamic range. The second supply potential is higher than the first, and is obtained by a step-up voltage device (23). The first supply potential is 3 V, and the second is 4.5 V.

Study of the oscillation condition of quartz oscillators by gyrator transformation

Abstract: The calculation of the oscillation condition is one of the main points of oscillator analysis. Its determination in finite terms allows one to calculate the steady state amplitude and frequency of the oscillator. Symbolic solutions provide an additional insight into the behavior of the circuit. As an example the sensitivity of the oscillator to parameter change can be expressed in an exact form. Numerical solutions are not as helpful as symbolic solutions in the design stage. We present a technique, based on the gyrator transformation, to set up the nonlinear equation network in a form suitable to be solved with analytical methods. We develop a symbolic program based on this technique. As an example, the symbolic program is applied to compute the exact expression of the steady state frequency and amplitude of the Van der Pol oscillator and the Colpitts oscillator.