Showing papers on "Relaxation oscillator published in 1997"

Accurate rc oscillator having peak-to-peak voltage control

Abstract: An RC oscillator circuit (10) within a microcontroller chip includes first and second comparators (16, 18) having their outputs respectively coupled to set and reset inputs of a flip-flop (20) whose output is coupled to a series RC network (22, 14) for controlling charging and discharging of a capacitor (14) of the RC network between precise high and low voltage levels (V2 and V1). One input of each comparator is coupled to the RC network, while the second input is coupled to a respective modified high and low threshold voltage level (Vh', V1'), so that the oscillator signal does not exceed the precise high and low voltage levels (V2, V1). The output frequency of the oscillator may be adjusted by selecting different values of the low voltage level (V1).

CMOS VCO's for PLL frequency synthesis in GHz digital mobile radio communications

Abstract: CMOS inductorless voltage controlled oscillator (VCO) design is discussed with the emphasis on low-noise, low-power, gigahertz-range circuits suitable for portable wireless equipment. The paper considers three VCO structures-one simple ring oscillator and two differential circuits. The design methodology followed optimization for high-speed and low-power consumption. The proposed linearized MOSFET model allows the accurate prediction of the operating frequency while the phase noise evaluation technique makes it possible to determine, through simulation, the relative phase-noise performance of different oscillator architectures. The measurement results of three VCO's implemented in 1.2-/spl mu/m CMOS technology confirm with the simulation predictions. The prototype VCO's exhibits 926-MHz operation with -83 dBc/Hz phase noise (@ 100 kHz carrier offset) and 5 mW (5 V) power consumption.

Method and system for calibrating a crystal oscillator

Abstract: A method and system are provided for calibrating a batch of devices each containing a circuit which is responsive to a control signal for producing a desired output which varies in accordance with a first predetermined function of a specific ambient condition, the control signal having a magnitude which varies as a second predetermined function of the specific ambient condition, the second function being based on data stored as a look-up table in a memory of the device and which must be individually calibrated for each device. In a preferred embodiment, the device is a digital temperature controlled crystal oscillator which produces a desired output frequency and includes a voltage controlled oscillator (VCO) responsive to a control signal having a magnitude which varies as a predetermined function of ambient temperature in order to compensate for temperature variations in the oscillator output frequency. For such an application, the invention requires the connection of an accurate frequency source to each oscillator in the batch so as to enable the output frequency of the oscillator to be equalized thereto or to a multiple thereof. In calibration mode, the digital equivalent of the resulting analog control voltage is stored; whilst in compensation mode it is extracted from the memory, converted to an equivalent analog voltage and applied to the VCO. The invention is also applicable to compensate for aging of crystal oscillators in the field without requiring reconfiguring the complete look-up table.

Temperature compensated frequency generating circuit

Abstract: The frequency of an integrated oscillator is held constant by using temperature compensation to compensate for the component variations due to temperature variations. A voltage controlled oscillator, which has temperature dependent components, is compensated with a temperature dependent control voltage. The frequency of many kinds of oscillators such as a relaxation oscillators and ring oscillators can be held constant when the operating current is held constant. The operating current is often derived from a current source, which is a voltage to current converter with a current equal to the ratio of a control voltage to a resistance. Since semiconductor resistance has a positive temperature coefficient is used to obtain a temperature invariant current source. The positive temperature coefficient is obtained with the difference junction voltage of two forward-biased pn junction voltages. The magnitude can be controlled by junction areas of the two junctions. The magnitude can also be amplified.

A relaxation-oscillator-based interface for high-accuracy ratiometric signal processing of differential-capacitance transducers

Abstract: For high-accuracy signal processing of differential-capacitance transducers, an interface circuitry is developed based on a relaxation oscillator. Two capacitors of the transducer are multiplexed by diode switches to form the op-amp-based integrator. The duty ratio of the oscillator output then measures the ratio of two capacitances. A circuit analysis shows that the interface can detect the capacitance change as small as 0.01% of the total capacitance. Experimental results are also given to confirm the analysis.

Resonant-tunneling transmission-line relaxation oscillator

Abstract: Experimental and numerical results are presented for a high-frequency oscillator consisting of a resonant-tunneling diode (RTD) series-embedded in a transmission line, one end of which is short circuited and the other end terminated with a load resistor. Like relaxation oscillators, the ac voltage across the RTD is a square wave. However, the current wave form (and hence the load wave forms) consists of a sequence of sharp pulses that are essentially locked to the fundamental mode of the transmission line.

Substrate biasing circuit having controllable ring oscillator

Abstract: A substrate biasing circuit is disclosed which includes a ring oscillator oscillating to a drive pulse signal, a charge pump circuit connected to the ring oscillator to receive the drive pulse signal and generating a substrate-bias voltage in response thereto, and a current control circuit connected to the ring oscillator. The ring oscillator includes a plurality of delay circuits and the current control circuit controls each of the delay circuits such that a current flowing there through is stabilized against the variation in power voltage and relative to a threshold voltage of a transistor for the charge pump circuit.

How Phase Noise Appears in Oscillators

Abstract: Wireless transceivers closely specify the phase noise in the local oscillator. Yet it is not very well understood how phase noise is predicted, especially in oscillators which do not use a passive resonator. It is also difficult to model flicker noise in the close-in phase noise spectrum. This is a qualitative discussion of the various physical processes responsible for phase noise production, particularly in CMOS oscillators, and it offers a common treatment of resonator-based oscillators, ring oscillators, and relaxation oscillators.

Inductive proximity sensor with a flat coil and a new differential relaxation oscillator

Abstract: A high-sensitivity flat-coil inductive proximity sensor microsystem has been realized and successfully tested. The flat coil, made with CMOS-compatible post processes, is connected to a versatile differential relaxation oscillator electronic interface. In this new and simple interface, the excitation, the signal extraction and amplification are assured by only one operational amplifier. Experimental results on the microsystem confirm that large output frequency variations occur when a metallic target approaches the sensor.

A differential relaxation oscillator as a versatile electronic interface for sensors

Abstract: A simple and versatile electronic interface circuit for sensors is presented. The novel interface circuit is based on a relaxation oscillator in differential configuration. In such a configuration, the sensitivity is strongly increased and compensations are made possible. It can be applied to resistive, capacitive and inductive sensors or detectors. Experimental and simulation results confirm the theory built up. High sensitivity is measured. Non-idealities of electronic components set the limit of attainable sensitivity.

Low-noise oscillator circuit having negative feedback

Abstract: A low-noise oscillator circuit with an amplifier element for negative feedback, specifically a transistor. In addition to a positive feedback of the oscillator transistor, provision is made for a negative-feedback loop with a pass band of 0 (thus DC coupling) to 1/4 to 1/100 of the oscillation frequency of the oscillator, in order to regulate out fluctuations of the current of the amplifier element.

A thick-film capacitive pressure sensor with improved linearity due to electrode-shaping and frequency conversion

Abstract: Various methodologies are applied to the measurement of pressure. Among them, the capacitive pressure sensor is one of the most useful devices due to its high performance-to-price ratio, reliability and low power consumption. However, the early versions of capacitive pressure transducers had a general reputation of being highly nonlinear. This paper discusses a design approach to overcome this problem by choosing a new electrode shaping and coupling the sensor with an electronic circuit based on a relaxation oscillator. Moreover, the output signal in the form of a frequency makes the distance transmission and the interfacing with digital systems easier. The theory of operation is presented with a description of the sensor's implementation in thick-film technology on ceramic substrates and with experimental results on its characterization.

A conditioning circuit for resistive sensors combining frequency and duty-cycle modulation of the same output signal

Abstract: A signal conditioning circuit based on a relaxation oscillator is presented for use with resistive transducers. Both the frequency and the duty-cycle of the output signal carry independent information coming from a pair of different sensors. Namely, the frequency of the output signal changes linearly with the resistance deviations detected by a Wheatstone bridge, while the duty-cycle is dependent on the resistance of a second sensor.

Voltage and temperature compensated ring oscillator for a memory device

Abstract: A refresh circuit of a memory device includes a ring oscillator with a frequency stabilizing circuit. The frequency stabilizing circuit produces compensated voltage signals in response to changes in supply voltage and temperature to modify the conductances of field-effect transistors of the frequency stabilizing circuit to compensate the conductive path of the discharge current of a capacitor from the ring oscillator in order to stabilize the oscillation frequency.

Heterolithic voltage controlled oscillator

Abstract: A voltage controlled oscillator includes a varactor (201) and a transistor (202) and a ground via (203), of epitaxially grown silicon that is etched to provide respective pedestals embodying the varactor (201) and the transistor (202) and the ground via (203), an L-C resonator circuit, the varactor (201) and an inductor providing a tank circuit that changes the frequency of the L-C resonator circuit, and that shifts the average frequency of the oscillator to that of an input voltage to the collector of the transistor (202).

Rectifying circuit for switching power supply and switching power supply using the rectifying circuit

Abstract: PROBLEM TO BE SOLVED: To obtain a switching power supply which suffers less rectification loss and facilitates output multiplication SOLUTION: A diode 2 and a capacitor 3 convert a rectangular-wave voltage applied to between the drain and the source of MOSFET 1 into a direct-current voltage, and supplies a comparator 4 and a gate drive circuit 3 with a positive voltage as positive power supply Diodes 6, 7, a capacitor 8, and a capacitor 9 form a negative power supply to the comparator 4 and the drive circuit 3 The comparator 4 leads the voltage of terminal 1 to a negative terminal and the voltage of terminal 2 to the positive terminal, and thus detects the voltage between terminal 1 and terminal 2 The gate drive circuit 3 amplifies the output of the comparator 4, and supplies the gate terminal of the MOSFET 1 with it

Relaxation oscillator of reduced complexity using cmos equivalent of a four-layer diode

Abstract: A relaxation oscillator of reduced complexity is described which can be constructed as part of a silicon integrated circuit. The current controlled oscillator includes complementary field effect transistors operating in enchancement mode. The drain of one FET is connected to the gate of the other FET and vice versa. The resulting CMOS circuit functions as a four-layer diode. A resistor is connected between the drains of both transistors. A storage capacitor is connected between the sources of both transistors. A current source is connected to charge the storage capacitor such that the frequency of an oscillator output signal is determined by the current generated by the current source.

Low-power CMOS current-conveyor relaxation oscillators

Abstract: The purpose of this paper is to investigate in detail the design of a current conveyor circuit suitable for implementation of low-voltage, low-power RC and crystal oscillators, and to show the design and performances of such oscillators. All circuits are based on the Fabre-Normand translinear conveyor. Circuits are biased in the subthreshold region whenever possible.

Magnetic field sensor based on a relaxation oscillator

Abstract: A new magnetic field sensitive device with frequency output has been developed using a novel relaxation oscillator. The frequency output is a linear function of the magnetic field variations from 1 Gauss up to 1000 Gauss. Experimental results show a sensitivity of 12 Hz/g. Further digital signals conditioning is achieved by means of a microcontroller.

Phase-locked loop with capacitive voltage divider for reducing jitter

Abstract: In a phase-locked loop comprising a phase detector (1), a loop filter (5) and a controlled oscillator (17) which are arranged on a common integrated circuit, interferences coupled into the substrate of the integrated circuit by other parts of the circuit are suppressed. In a first embodiment of the invention, this object is achieved in that the controlled oscillator (17) is preceded by a capacitive voltage divider (9) which comprises at least two capacitances (10, 12), the controlled oscillator (17) is controlled in dependence upon the output signal of the capacitive voltage divider (9), and the capacitive voltage divider (9), together with the phase detector (1), the loop filter (5) and the controlled oscillator (17) is arranged on an integrated circuit. In accordance with a second embodiment of the invention, the reduction of interference is achieved in that the controlled oscillator (17) has a differential structure and comprises at least two voltage-controlled current sources (18, 19) whose circuits are coupled to a power supply potential and to a substrate on which the integrated circuit is arranged, the controlled oscillator (17) has an output stage (20) which is arranged behind the voltage-controlled current sources (18, 19) and generates two differential digital signals in dependence upon the differential signals applied thereto, which differential digital signals are generated with a high edge steepness by means of switching between two potentials and are applied to amplifier stages (56, 57) which are arranged between power supply potential and reference potential and supply two differential output signals operating at reference potential.

Nonlinear time-domain analysis of injection-locked microwave MESFET oscillators

Abstract: In this paper, injection-locked MESFET oscillators are analyzed using several numerical models. The injection-locking behavior of the van der Pol equation and of a more complex representation using the Curtice-Cubic MESFET model are investigated. Analysis and experimental results are compared for an NE71083 transistor oscillator operating at 0.5 GHz. The deficiencies of using a van der Pol oscillator model are pointed out. Time-domain results from the complex model exhibiting multicycle and apparently chaotic behaviors are also examined, and point to problems with common nonlinear simulation techniques for these circuits.

1-V low-noise 200 MHz relaxation oscillator

Abstract: This paper presents a high-frequency current-controlled relaxation oscillator designed for ultra-low voltage supply (0.9 V). The choosen relaxation oscillator topology provides both high frequency and low noise characteristic. Simulated results are verified by measurements on a full-custom integrated circuit. The tuning range extends from 1 to 180 MHz with supply current limited to 1.1 mA. At a 200 kHz off set from the oscillator frequency, the measured phase noise is-89 dBc/Hz.

Stable frequency oscillator having two capacitors that are alternately charged and discharged

Abstract: An oscillator circuit capable of being fully implemented in integrated circuit form and having a first current source for charging a first capacitor so as to produce a time varying voltage which is sensed by a first comparator when the voltage reaches a predetermined threshold level. The circuit further includes a second current source for charging a second capacitor so as to produce a further time varying voltage which is sensed by a second comparator when the voltage reaches the predetermined threshold voltage. The output of first and second comparators are combined so as to produce the output clock signal, with the first cycle segment of the clock having a duration determined by the first comparator output and the second cycle segment of the clock having a duration determined by the second comparator output.

Low drive level crystal oscillator circuit

Abstract: This paper presents a design method of a transistor crystal oscillator circuit in which the steady oscillation occurs at very low drive level. It has been shown that the reduction ratio of up to 1/50 of the resonator current can be obtained.

Ultrasonic generator circuit incorporating a power oscillator and a feedback loop

Abstract: An ultrasonic generator circuit is described which comprises a resonant LC power oscillator circuit for driving an ultrasonic transducer, the resonant circuit comprising a voltage controlled switching element (an integrated gate bipolar transistor is preferred), and feedback being provided via a feedback transformer whose primary is connected in the resonant circuit, the secondary of the feedback transformer being connected to a feedback signal converter which, in dependence upon feedback current induced in the secondary of the feedback transformer, applied a feedback voltage to the input of the voltage controlled switching element (Fig. 6).

Multi-phase pulse-width-modulation power converter

Abstract: An N-phase power converter uses a ring oscillator to generate a series of switching signals having substantially equally distributed phase relationships with respect to one another. The ring oscillator is formed from an alternating string of inverters and RC networks with the voltage over each capacitor of each RC network provided to a phase comparator. The phase comparators shape a saw-tooth waveform present over each capacitor into a pulse-width-modulated switching signal that drive switches which alternately charge and discharge inductors. One terminal of each inductor is coupled to common node at which the converter output voltage is provided. A feedback unit generates a feedback signal is used to vary the pulse width of the switching signals.

Oscillator-based signal conditioning for resistive sensors

Abstract: A signal conditioning circuit for resistive sensors is presented. It is based on a relaxation oscillator in which both the frequency and the duty-cycle of the output signal simultaneously carry information from a pair of different sensors. The output frequency is linearly related to the resistive unbalance of a Wheatstone bridge, while the duty-cycle is independently controlled by a second sensor. For this purpose, a thermoresistor may be used for thermal compensation of the primary sensor. The design, analysis and experimental characterization of the circuit and its application to a thick-film pressure sensor are reported.

Supply voltage insensitive charge/discharge type oscillator and method

Abstract: An oscillator circuit is described which produces a periodic oscillator output signal. The frequency of the oscillator output signal is essentially independent of the supply voltage provided to the oscillator circuit. The oscillator circuit includes a capacitor which is periodically charged and discharged. A high trip point inverter and a low trip point inverter detect the voltage level of the capacitor and set and reset, respectively, a flip-flop. The flip-flop produces an output signal which controls the charge and discharge of the capacitor through charging and discharging circuit paths, respectively. The impedance presented by the charging and discharging circuit paths varies as a function of the supply voltage, such that the high and low trip point inverters are switched at a frequency which is essentially independent of the supply voltage magnitude. The oscillator output signal is derived from the flip-flop output signal.

Voltage compensated oscillator and method therefor

Abstract: A voltage compensated oscillator circuit having a resistor capacitor (RC) circuit for setting a frequency of oscillation for the oscillator circuit. A switching circuit with hysterisis is coupled to the RC circuit for providing upper and lower threshold limits. The upper and lower threshold limits being used for controlling the direction of switching of the oscillator circuit. By adjusting the upper and lower threshold limits, one may compensate for voltage signal fluctuations so that the frequency of oscillation will not change due to power supply voltage fluctuations.

Voltage or current controlled multivibrator oscillator circuit

Abstract: An oscillator circuit comprises two main transistors (Q 1 , Q 2 ), between which is provided a positive feedback by connecting each transistor base to the collector of the other transistor via buffer transistors (Q 3 , Q 4 ). A capacitor (C) is connected between the emitters of the main transistors. The frequency of the oscillator is controlled by two current sources ( 11, 12 ), which control the current (I 2 , I 2 ) flowing through the capacitor (C). Additionally, a compensation current (Icom) is conducted via collector resistors (Rc 1 , Rc 2 ) of the main transistors such that the current flowing through each resistor is essentially constant and independent of the control current (I 1 , I 2 ), so the signal amplitude of the oscillator does not change during frequency control.