Showing papers on "Relaxation oscillator published in 2007"

Foundations of Oscillator Circuit Design

Abstract: Offering broader coverage than other oscillator design books on the market, this comprehensive resource considers the complete frequency range, from low-frequency audio oscillators to more complex oscillators found at the RF and microwave frequencies. Packed with over 1,200 equations, the book gives you a thorough understanding of the principles and practice of oscillator circuit design and emphasizes the use of time-saving CAD simulation techniques. From the theory and characteristics of oscillators, to the design of a wide variety of oscillators (including tuned-circuit, crystal, negative-resistance, and relaxation oscillators), this unique book is the one-stop reference you'll turn to again and again when working on your challenging projects in this field. Supplementary Material: For the errata of this book please visit www.artechhouse.com/static/downloads/gonzalez_errata.doc

Setting a discharge rate and a charge rate of a relaxation oscillator circuit

Abstract: An apparatus and method for setting a ratio of a discharge rate to a charge rate for measuring a capacitance on a sensor element of a sensing device. The apparatus may include a sensor element of a sensing device, a relaxation oscillator having a first and a second programmable current source, and a ratio decoder to receive a ratio of a discharge rate to a charge rate, and to set the first and second programmable current sources based on the received ratio.

Sinusoidal and Relaxation Oscillations in Source-Coupled Multivibrators

Abstract: The paper considers the differential equation describing sinusoidal and relaxation oscillations of the source-coupled multivibrator. The transition from one form of oscillations to another, when the coupling capacitor is increasing, is explained by modifications in the shape of the central branch of the isocline of horizontal tangents on the phase plane of this differential equation. The formulas for amplitude and frequency calculations in sinusoidal operation are found. The calculations of transistor switching time and period for relaxation oscillations are provided as well. The results were verified in simulations.

ASIC front-end interface with frequency and duty cycle output for resistive-bridge sensors

Abstract: An application specific integrated circuit (ASIC) front-end interface in 0.7-μm CMOS for resistive-bridge sensors is proposed. The circuit is based on a relaxation oscillator where the frequency of the rectangular-wave output is related to the fractional bridge unbalance, and the duty cycle depends on the overall bridge resistance, which typically is related to temperature. In this way, two independent pieces of information are simultaneously and cost-effectively carried on the same output signal. The bridge is driven at constant current, this avoids accuracy degradation with remotely placed sensors and enables a first-order thermal compensation for piezoresistive semiconductor sensors. The circuit has been characterized by means of a 1-kΩ reference bridge showing frequency and duty cycle sensitivities of 60.4 Hz/(1000 ppm) and 0.276%/(mΩ/Ω), respectively, at a central frequency of about 6.4 kHz. The circuit has also been tested with a piezoresistive SiC sensor operated at temperatures up to 150 °C, showing results in agreement with theoretical predictions.

1.1-μm-range tunnel junction VCSELs with 27-GHz relaxation oscillation frequency

Abstract: We have developed novel 1.1-μm-range InGaAs VCSELs with buried type-II tunnel junctions for high-speed optical interconnections. A relaxation oscillation frequency of 27 GHz was achieved. Error-free 30-Gbps operations were demonstrated using directly modulated multi-mode VCSELs.

The Effect of Mismatches and Delay on the Quadrature Error of a Cross-Coupled Relaxation Oscillator

Abstract: Cross-coupled relaxation oscillators can produce two highly accurate quadrature output signals (Verhoeven, 1992). We present a high-level model of these oscillators in terms of circuit parameters, from which we obtain explicit equations for duty-cycle, oscillation frequency, and quadrature error. They show the influence on the oscillator performance of component mismatches and other nonideal effects, such as delays. The results provide useful guidelines for the design of high performance oscillators. The theoretical results are confirmed by simulation and by measurements on a test chip.

Experimental Evaluation of Phase-Noise and Quadrature Error in a CMOS 2.4 GHz Relaxation Oscillator

Abstract: Contrary to what happens with LC oscillators, the increase of coupling in cross-coupled relaxation RC-oscillators leads to a lower quadrature error and lower phase-noise. We present a 2.4 GHz CMOS quadrature relaxation oscillator, and show the measurements confirming this property. Increasing the coupling block gain, the oscillator phase-noise is reduced from -97 dBc/Hz to -104 dBc/Hz @ 1 MHz. The quadrature error is reduced from 4.3deg to 0.8deg. These results show that RC quadrature oscillators may be a practical alternative for RF transceiver applications.

A GaAs acoustic sensor with frequency output based on resonant tunneling diodes

Abstract: This paper reports a novel acoustic sensor with a frequency output based on AlAs/InxGa1−xAs/GaAs resonant tunneling diode (RTD). The RTD is incorporated in a 1m thick membrane and the fabrication technology of the membrane is based upon the selective etch of GaAs with AlAs as an etch stop layer. A relaxation oscillator is obtained with the RTD biased in the negative differential resistance (NDR) region. Acoustic pressure applied to the RTD changes the frequency of oscillation due to the shift in current–voltage characteristics. The main feature of this sensor type is the direct frequency output, which is linearly dependent on pressure, and the linear sensitivity can be up to 21 kHz/kPa. © 2006 Elsevier B.V. All rights reserved.

Novel Signal Conditioning Circuit for Push-Pull Type Capacitive Transducers

Abstract: A novel signal conditioning circuit suitable for push-pull type capacitive transducers is proposed. The circuit developed is capable of providing a linear output over a wide range of values of the physical quantity being measured even when the transducer output has an inverse relationship with the measurand. The push-pull type capacitive transducer becomes an integral part of a relaxation oscillator, the duty cycle ratio of the output of which becomes proportional to the measurand. The various sources of error in the circuit are analyzed, and quantitative expressions to estimate such errors are derived. Results obtained from tests on a prototype indicate that the circuit possesses very low errors

Hysteresis Circuit Without Static Quiescent Current

Abstract: A hysteresis circuit including a comparator and capacitive voltage divider circuit. The capacitive voltage divider circuit includes a first capacitor coupled between an input terminal and a positive comparator input, a second capacitor coupled between ground and the positive comparator input, and a third capacitor coupled between the comparator output and positive comparator input. A reference voltage is applied to the negative comparator input. The comparator is powered by the input signal provided on the input terminal. When the voltage on the positive comparator input is less than the reference voltage, the third capacitor is effectively coupled in parallel with the first capacitor. When the voltage on the positive comparator input is greater than the reference voltage, the third capacitor is effectively coupled in parallel with the second capacitor.

A Low-Noise Switched-Capacitor Front End for Capacitive Sensor

Abstract: This paper presents the analysis and design of an integrated low-noise switched-capacitor front-end circuit for capacitive sensors. The interface has been implemented with a relaxation oscillator. To prevent overload of the input amplifier for large input signals, a negative-feedback circuit controls the charge-transfer speed. It is shown; that this negative feedback can also be used to optimize the noise performance of the interface. The circuit has been designed and implemented in 0.7 mum standard CMOS technology. The effects of any additive and multiplicative interface errors have been reduced by applying three-signal auto-calibration. Experimental results show that application of negative feedback yields a resolution of more than 16 bits for measurement time of about 100 ms, which is at least 1 bit better than that of an earlier designed interface.

Smart sensor interfacing circuit using square-rooting current-to-frequency conversion

Abstract: A universal sensor interfacing circuit is presented in this paper. It is capable of giving a digital output directly proportional to various types of measured quantities, where those measured quantities are proportional to the square root of some other type of quantity. This sensor interfacing circuit is a square-rooting current-to-frequency converter. The design is based on two current-controlled resistors in CMOS technology with bisection of the input voltage used in place of the ordinary resistors within the relaxation oscillator. There is no need for highly stable voltage or current references in the proposed design. The temperature stability of the design is achieved without the need for any specific setting of the process parameters. Experimental results, obtained on a circuit implemented by discrete components, confirm the predictions of the analysis performed. The relative errors are less than 1% for the input current range from 12 µA to 650 µA, and for the output frequency range from 231 Hz to 2....

Synchronization of two LC-oscillators using nonlinear models

Abstract: Synchronization of two LC-oscillators is a deeply nonlinear process. We consider synchronization of two van der Pol oscillators using different coupling circuits (four cases are considered), and coupled via first harmonic. We derive the equations for calculation of the synchronization frequency, and the equations for the oscillation amplitudes. It is shown that, in the general case, the synchronization frequency is different from the frequencies of individual oscillators before coupling. The oscillation amplitudes are also not equal: one oscillator becomes a master, and the other oscillator becomes a slave.

Study of Speed Enhancement of a CMOS ring VCO

Abstract: Positive feedback has been added to a fully differential CMOS amplifier. With the introduction of positive feedback, the delay time reduces and the speed of operation increases. An even or odd number of stages can be cross coupled or directly coupled to form a ring Voltage Controlled Oscillator or Current Controlled Oscillator (VCO/CCO). Pspice simulation shows an improvement (increase) of speed of around 167 %. Instead of using positive feedback if we use negative feedback then also the speed improves but it requires a higher value of feedback resistance, which is not favoured in integrated circuit fabrication. Here the typical supply voltage requirement is ±2 volt. Using this amplifier some applications have also been discussed.

Wireless communication unit, integrated circuit comprising a voltage controlled oscillator and method of operation therefor

Abstract: A wireless communication unit (400) comprises a frequency generation circuit (423) employing a phase locked loop (PLL) circuit comprising a voltage controlled oscillator (VCO) (1100) having a modulation port for directly modulating a signal output from the VCO. The VCO is operably coupled to at least one switch (1121, 1122) and a capacitor bank (1105) comprising one or more varactors. A controller (1130) is arranged to switch-in one or more varactors associated with the modulation port of the PLL circuit the number of switched-in varactors varying proportionally to a piecewise approximation of 1/f2. This allows the modulation port gain KmOd of the VCO to remain substantially constant when the frequency varies. In addition, or alternatively, the PLL circuit may comprise a VCO having a tuning port for controlling a frequency of a signal output from the VCO. The controller (1130) is arranged to switch in one or more varactors associated with the tuning port of the PLL circuit, the number of switched-in varactors varying proportionally to a piecewise approximation of 1/f3. This allows the ratio Kv/N to remain substantially constant when the frequency varies, Kv being the turning port gain of the VCO and N is a division ratio of a divider (305) in the feedback loop of the PLL.

Voltage controlled oscillator module with ball grid array resonator

Abstract: A voltage controlled oscillator (VCO) assembly and module incorporating a ball grid array resonator as part of the tank circuit of the voltage controlled oscillator. The VCO module preferably incorporates at least an oscillator circuit, the tank circuit, and an output buffer stage circuit all defined by a plurality of interconnected electrical/electronic components including the ball grid array resonator which are mounted to a printed circuit board. In another embodiment, the oscillator assembly also includes a phase-locked loop circuit defined at least in part by an integrated circuit mounted to the printed circuit board.

Sinusoidal and relaxation oscillations in emitter-coupled multivibrators

Abstract: The paper investigates transition from sinusoidal to relaxation oscillations in emitter-coupled multivibrator. First, the differential equation for sinusoidal regime is obtained, and the frequency and amplitude are calculated. Then, the transition from sinusoidal to relaxation oscillations is traced using the phase plane of this equation. The transition is explained by modification of the shape of central branch for the isocline of horizontal tangents. Finally, the sinusoidal regime approximation for static impedance seen by the coupling capacitor is used to calculate the oscillation period in relaxation oscillation. The results were verified in simulations.

A DC-Powered High-Voltage Generator using a Bulk Pt-Rh Oscillating Micro-Relay

Abstract: This paper reports a high voltage generator formed by the hybrid assembly of a micromachined relay and a wound-wire inductor or transformer. The relay is micro-electrodischarge machined from Pt-Rh bulk metal foil, and consists of a normally-closed switch that is part of a DC-powered electrothermal relaxation oscillator. The use of this material permits the relay to be operated in air, without the need for inert packaging. It also provides a resistance of <2 Omega (including both the actuator and the contact), which makes it amenable to low drive voltages. Using an input of 5 V and a 56 mH transformer with a turns-ratio of 46, peak pulsed outputs of 1200 V are obtained. A DC output of 276.5 V is obtained for an output power of 76 mW.

An integrated switched-capacitor front-end for capacitive sensors with a wide dynamic range

Abstract: This paper presents the analysis and design of an integrated switched-capacitor front-end circuit for capacitive sensor with a wide dynamic range. The interface has been implemented with a relaxation oscillator. A negative-feedback circuit controls the charge-transfer speed, to prevent the overload of the input amplifier for large input signals. It has been shown, that proper functioning of this circuit is limited to a certain range of one of the parasitic input capacitances. Solutions to extend this range have been proposed. The circuit has been designed and implemented in 0.7 mum standard CMOS technology. The effects of any additive and multiplicative interface errors have been reduced by applying three-signal auto-calibration. Experimental results show that application of negative feedback yields a linearity of about 50times10~6 (14 bits) for the capacitor range of 1 pF to 300 pF, with a 16 bits resolution for a measurement time of 100 ms.

Breakdown of synchronization in chaotic oscillators and noisy oscillators

Abstract: In this study, the breakdown of synchronization observed from four coupled chaotic oscillators is investigated. In order to understand the phenomenon, the model of coupled modified van der Pol oscillators with noise is considered. The comparison of the coupled chaotic oscillators with the coupled modified van der Pol oscillators with noise gives us some interesting results.

Modeling transit-time microwave tubes

Abstract: An excitation model for TM-mode cylindrical cavities driven by a modulated electron beam with application in transit-time microwave tubes is developed. It is shown that the slowly time varying amplitude of the self-sustained oscillations is described by a reduced form of the classical van der Pol equation. Encompassing the relevant parameters of the dynamics of the rf field-electron beam interaction (nonlinear conductance of the electronic beam, the ratio R/Q of the resonant cavity, dc beam resistance), an excitation equation is then obtained from which expressions for the starting current and saturation amplitude are readily derived.

Novel Signal Conditioning Circuit for Push-Pull Type

Abstract: A novel signal conditioning circuit suitable for push- pull type capacitive transducers is proposed. The circuit developed is capable of providing a linear output over a wide range of values of the physical quantity being measured even when the transducer output has an inverse relationship with the measurand. The push- pull type capacitive transducer becomes an integral part of a relax- ation oscillator, the duty cycle ratio of the output of which becomes proportional to the measurand. The various sources of error in the circuit are analyzed, and quantitative expressions to estimate such errors are derived. Results obtained from tests on a prototype in- dicate that the circuit possesses very low errors. Index Terms—Capacitive transducer, relaxation oscillator, signal conditioning.

Onset and Saturation of the Electric-Field Amplitude in Transit-Time Tubes

Abstract: The monotron lumped equivalent circuit can be thought of as consisting of a physical tuned circuit connected to a resistor of negative resistance. For transit times near (N+1/4)T, where N is an integer and T the oscillation period, electron bunches are formed and upon reaching the cavity's end plate in a decelerating phase of the RF field the bunches transfer energy to the cavity. The relation between current and voltage is set by the beam conductance, which is always non linear, so that for one amplitude will there be a given ratio between current and voltage. From the equation of motion of the beam electrons interacting with the RF fields, such relation - the electronic beam nonlinear conductance G(V2) - is found by expanding the conversion efficiency up to the tenth power of the RF voltage amplitude. Then using G(V2) in the energy balance equation (relating the RF power losses in the cavity and the microwave power radiated by the electron beam) we arrive at the van der Pol's equation, just describing the non linear growth and the stationary generation of the electromagnetic mode operating in the cavity driven by the externally injected beam. It is shown that the analytic expressions for the self-excitation condition and for the saturation of the wave growth found on the basis of a 1-D circuit model are in excellent agreement with a full scale 2 frac12 -D particle-in-cell simulation.

Synchronous Oscillator Using High Speed Emitter Couple Logic (ECL) Inverters

Abstract: This paper presents a synchronous oscillator using a high speed low voltage Emitter Coupled Logic (ECL) inverter. Using the positive feedback the locking range increases, compared to the oscillator without any positive feedback. A maximum improvement (increase) of locking range of around 172% was obtained from circuit simulation as well as from practical circuit, using discrete components. Here the supply voltage requirement is 2.1 volts.