Showing papers on "Relaxation oscillator published in 1975"

Studies of relaxation oscillations in organic dye lasers

Abstract: The transient phenomena of relaxation oscillations and "initial spikes" in organic dye lasers are studied experimentally and theoretically. Both damped relaxation oscillations and initial spikes are clearly observed in N 2 laser-pumped dye lasers under appropriate conditions which are furthermore shown to agree with theoretical considerations. Linearized rate equations obtained with small-signal approximation are used to describe the initial-spiking phenomenon; for the more general phenomenon of relaxation oscillations computer solutions of the coupled rate equations are obtained. Comparisons with experimental observations show excellent qualitative agreement. Based on the results of these studies, a general technique using the idea of controlled resonator transients is described for tunable subnanosecond pulse generation from laser-pumped dye lasers in the near UV and the visible region of the spectrum.

Power supply for a laser or gas discharge lamp

Abstract: A regulated power supply for a laser or gas discharge lamp employs a variable duty cycle oscillator to control the output voltage level. Output current to the laser or lamp load is maintained at a constant value by a feedback loop that controls the oscillator duty cycle. The output current is sensed by a novel circuit which employs a voltage regulator in series with the current return path. A change in output current causes a concomitant change in voltage across a resistor divider that shunts the voltage regulator. The voltage from this divider is a feedback signal that is supplied to a duty cycle modulator which controls the oscillator duty cycle. Another feedback signal is derived in delayed response to voltage output in excess of a certain high value. This feedback signal, which occurs, e.g., when the laser or lamp load does not ignite within a certain time period, also modifies the oscillator duty cycle so as to reduce the output voltage to a level that can be maintained continuously without damage or overheating of any circuit component.

Relaxation Oscillations in Point Contact Josephson Junctions.

Abstract: Negative resistance regions have been observed on the static I−V curves of point−contact Josephson junctions when dc biased with a low−impedance source. An equivalent circuit model has been developed which successfully explains the experimental results in terms of relaxation oscillations. It is also found that such junctions can be operated either as a one−port amplifier for signals at 5 MHz or as a 36−GHz heterodyne mixer with large conversion gain.

One shot multivibrator circuit

Abstract: An improved one shot multivibrator circuit is described which is particularly adapted for use with field-effect transistor (FET) manufacturing techniques such as metal oxide semiconductor (MOS) large scale integration (LSI) manufacturing techniques. Such a one shot multivibrator circuit is particularly adapted for FET application because the period of its output pulse is independent of the threshold voltages of the transistors used in the circuit design. The one shot multivibrator circuit comprises a capacitor for fixing the period of the output pulse; a bias network including a current mirror as a constant current source for charging the capacitor; a first inverter stage comprising a switching transistor and a load transistor for controlling the charging and discharging of the capacitor; and a second inverter stage as the output stage for providing the output pulse having its turn-on controlled by the first inverter stage and its turn-off controlled by the voltage level on the capacitor.

Fault current flux detector - trips on AC or DC fault or component failure

Abstract: The current flux determining device has a magnetic flux conductor linked with a current loop and carrying the collected flux, especially for application in a fault current circuit breaker, which responds to both AC and DC faults and to changes in normal operation due to component failure in the instrument itself. The current loop is the constituent part of a detector circuit which determines its induction and means to monitor the characteristics of the detector circuit are also provided. The detector circuit may be an oscillatory circuit or the frequency determining part of a relaxation oscillator.

Electric remote control transmitter

Abstract: An electronic remote control transmitter employs a two transistor cascade oscillator having positive and negative feedback loops. The oscillator voltage is supplied through a switch assembly containing a plurality of momentary contact switches to a pair of voltage dividers supplying signal voltages in predetermined ratios to a two branch circuit in the negative feedback loop. One branch contains an inductor and the second branch a capacitor. Closure of any switch completes the DC circuits for the transistors. Signal voltage is supplied to the branches to produce a minimum amplitude, zero phase shift condition which establishes oscillation at that predetermined frequency. The output of the oscillator is amplified by a third transistor and supplied to an ultrasonic transducer for generating acoustical control signals.

Means for controlling the phase or frequency output of an oscillator in a loop circuit

Abstract: A device for controlling, by means of a phase comparator which receives annput signal, the phase or frequency output of a voltage controlled oscillator connected with the phase comparator in a phase locked loop, this loop being also provided with a branch circuit including a high pass filter or appropriate characteristics.

Integrated circuit relaxation oscillator

Abstract: An integrated circuit relaxation oscillator includes a capacitor, a resistor forming a conductive path for charging the capacitor, a transistor for discharging the capacitor, and a control circuit responsive to the level of charge on the capacitor for controlling the conduction level of the transistor. The control circuit has a relatively high trip point while it is in one state and during the time that the capacitor is being charged, and a relatively low trip point while it is in a second state and during the time that the capacitor is being discharged. The control circuit is balanced, such that variations in process parameters and variations in the voltage level of the power supply do not appreciably affect the period of the oscillatory output signal.

Temperature compensated solid-state oscillator

Abstract: Temperature-compensated solid-state oscillators. A temperature sensitive voltage regulator provides to the oscillator a supply voltage which varies in accordance with a temperature-dependent voltage across a diode junction in the oscillator timing circuit. The oscillator frequency thereby remains substantially constant over a wide range of ambient temperatures and input voltages.

Luminance controlled indicator in camera view finder

Abstract: An automatically light adjusted luminous indicator observable through a camera view finder includes a photoconductor exposed to the camera incident light and either constitutes or controls the resistance component of a frequency controlling RC network of a relaxation oscillator. The output of the relaxation oscillator controls a bi-stable multivibrator whose output is coupled through a switching transistor to the primary of a transformer whose secondary is connected to a light emitting member such as an electroluminescent device or a light emitting diode. The parameters of the network are adjusted so that the luminosity of the indicator and viewed image are about equal or within any desired ratio range. The photoconductor may also control an exposure control network.

Nonlinear Analysis of a Family of LC Tuned Inverters

Abstract: four widely used self-oscillating dc-to-square-wave parallel inverters which employ an inductor-capacitor tuned network to determine the oscillation frequency are reduced to a common equivalent RLC network. The techniques of singular-point analysis and state-plane interpretations are employed to describe the steady-state and transient ient behavior of these circuits and to elucidate the three possible modes of operation: quasi-harmonic, relaxation, and discontinuous. Design guidelines are provided through a study of the influence of circuit parameter variations on the characteristics of oscillation and on frequency stability. Several examples are provided to illustrate the usefulness of this analysis when studying such problems as transistor emitter-to-base junction breakdown during oscillations and the design of starting circuits to insure self-excited oscillations in these inverters.

Astable multivibrator circuit

Abstract: The start-up delay of an externally synchronized astable multivibrator is reduced by placing a low impedance path between ground and the base electrode of a transistor in the input circuit to the multivibrator in response to the signal which turns on the multivibrator.

Oscillator circuit whose frequency is voltage controllable which contains a comparator

Abstract: An oscillator utilizing a voltage comparator having hysteresis characteristics for producing a pulse train. The width of the pulses in the train is controlled by the charging rate of a capacitor coupled to one input of the comparator and the period of the pulse train is controlled by the discharge rate of this capacitor. The discharge rate and hence the oscillator frequency may be varied in response to a control voltage. Compensating elements ensure that the pulse width is highly stable with respect to temperature variations. The oscillator when in a feedback control circuit, produces oscillations at a frequency whose value is linearly related to the feedback control voltage.

Double-diode trapatt pulse generator with applications to avalanche-diode research

Abstract: Improvements in trapatt pulse generators are described. By using two diodes in a push-pull configuration, pulses around 250 ps duration with up to 800 W peak power can be produced with repetition rates around 1 GHz. Measurements of diode breakdown under controlled high-speed voltage pulses from such a generator have been made on X-band trapatt diodes. These measurements show that relaxation-type oscillations can start in resistive circuits and thus support the relaxation oscillation theory for the starting mechanism of trapatt oscillations. They further suggest that high-frequency trapatt devices may have difficulty in operating efficiently at frequencies lower than some particular value determined by the relaxation oscillations.

Phase-locking loop with variable bandwidth filter

Abstract: A phase-locking network at the receiving end of a transmission channel carries an incoming wave of predetermined frequency matching the operating frequency of a local oscillator the incoming wave and the locally generated oscillations being fed to respective inputs of a phase comparator producing a control voltage delivered through a low-pass filter to the oscillator for reducing any existing phase difference. The signal path between the phase comparator and the oscillator includes one or more nonlinear impedance elements, either within the filter or in cascade therewith, which lowers the effective series resistance of the path in the presence of a high control voltage and thereby increases its bandwidth during an acquisition period as compared with steady-state operation.

Time-keeping apparatus

Abstract: A time-keeping apparatus uses a crystal oscillator and electronic frequency dividers, as well as an electronically regulated mechanical time-keeping system (balance wheel system) which is part of an indicating system. The indicating system is driven at at least two different rpm's; at least one of these rpm's is effectively controlled to be higher and at least one of these rpm's can be controlled to be lower than a nominal rpm corresponding to the frequency of oscillation of the crystal oscillator, which may be of quartz. A storage circuit, in the form of a bistable multivibrator, has one input coupled to an output of a frequency divider which, in turn, is controlled by the output from the crystal oscillator. The other input to the storage circuit is provided with input pulses derived from the indicating system or from the electronically controlled mechanical time-keeping system, which have very nearly the same frequency as the pulses of the output of the frequency divider fed from the crystal oscillator. The output from the bistable multivibrator is coupled, via a switching circuit, to the electronically controlled balance wheel system.

A Wide Range Voltage-Controlled Oscillator

Abstract: An understanding of the fundamental constraints which limit the performance of controlled oscillators has permitted the development of a VCO having exceptional performance. The output frequency is relatively independent of power supply and temperature and is proportional to the controlling voltage for at least four decades. The switching circuitry is operated in a nonsaturating mode which allows frequency operation to 5 MHz. The entire circuit is compatible with monolithic IC technology.

A Study on Mechanism of Oscillation in Sonic Oscillators : 1st Report, Mathematical Model of Oscillators Operated by Water

Abstract: A wall-attached fluidic element is caused to oscillate by interconnecting two control ports with a conduit. The oscillator is termed a sonic oscillator, which is usually operated by air. In this study, however, a mathematical model of the oscillator operated by water is introduced and its propriety is examined experimentally. The basic equation describing the behaviour of the oscillator is derived from several assumptions and it results in the generalised equation of Lienard. On the basis of this equation, the mechanism of oscillations is theoretically investigated and it is shown that oscillations are caused by the negative resistance in the input characteristics of the wall-attached element. Theoretical results are in satisfactory agreement with experimental results.

Modulation linearization of a frequency-modulated voltage controlled oscillator, part 3

Abstract: An analysis is presented for the voltage versus frequency characteristics of a varactor modulated VHF voltage controlled oscillator in which the frequency deviation is linearized by using the nonlinear characteristics of a field effect transistor as a signal amplifier. The equations developed are used to calculate the oscillator output frequency in terms of pertinent circuit parameters. It is shown that the nonlinearity exponent of the FET has a pronounced influence on frequency deviation linearity, whereas the junction exponent of the varactor controls total frequency deviation for a given input signal. A design example for a 250 MHz frequency modulated oscillator is presented.

Device Physics of a New TRAPATT Oscillator

Abstract: A new circuit for TRAPATT operation of avalanche diodes has been fabricated and tested. Operation of diodes in the circuit has also been studied via computer simulation. Results are given ! n this paper and discussion is given on the internal dynamics of the field shock-front formation, based on the computer simulation. T1.e major features of the new TRAPATT oscillator are 1) that TRAPXI'T oscillation can start without delay, and hence the oscillator is usefrl for short-pulse operation, 2) that TRAPATT oscillation can be 6113- tained at a relatively low current, and CW operation may be possiblle, and 3) that the TnAPATT frequency is a decreasing funct;on of llle bias current. INTRODUCTTON In a conventional TRAPATT circuit (l), (a) the "over- voltage" required to initiate the TRAPATT action in the avalanche diode is obtained from a reflected travelirg wave of the "voltage drop" of the previous cycle. The energy storage in the circuit is electromagnetic. The Q lof the circuit, required to produce the sharp spike, is high and the initial oscillation is believed to be powered by the IMPATT action of the diode. TRAPATT action is observtd only after a time duration corresponding to many IMPAVT periods aft.er the application of the bias current pulse. We have studied a new and simple TRAPATT circuit via computer simulation and have observed corresponding experimental results in an actual circuit, shown schema1,i- cally in Fig. 1. The major features of the circuit are ..) that TRAPATT action can be sustained at a relatively 1cw current (J E O.Xqv,Nd) and 2) that the TRAPATT fre- quency is a decreasing function of the average current. The essential element of the circuit is the metal d.isc which forms a "lumped" capacitor with the ground plane and is in contact with the diode. Superficially, the oscillatx resembles the relaxation oscillator investigated by Ward and Udelson (3), Hoefflinger (4), and Carlson (SI. It is distinguished from the latter in that the TRAPATT fne- quency is a decreasing function of the average current. This reversed frequency-average current relation is sox e- what similar to Ward's more recent computations (3) although his result was not verified by experiment. Our oscillator is new and unique in the sense that the disc capacitor can also act as a radial resonator. Thus the d.sc and the ground plane together form a complete TRAPA.TT circuit. Furthermore, the manner of interact'ion between the circuit and the diode is different from the c1assic:al TRAPATT oscillator as discussed in Section 11. Two moc.es of TRAPATT oscillation, designated as the "pure" mode and the "mixed" mode, have been identified in connection with

Nonlinear analysis of a family of LC tuned inverters

Abstract: A family of four static dc-to-square-wave transistor inverters has been analyzed employing state-plane techniques to describe the quasi -harmonic mode of oscillation commonly encountered in this family, as well as the less familiar relaxation oscillation and its limiting case, discontinuous oscillations. Design guidelines are provided through a study of the sensitivity of parameter changes which affect the oscillation characteristics of the inverter and its frequency stability. The analysis of one particular inverter of this family in which the avalanche breakdown of the transistor emitter-to-base junction occurs is presented. Finally the starting characteristics of this family of inverters are discussed with two illustrative examples. It is shown in this paper that close relationships exist between the family of LC tuned inverters and the previously analyzed saturable-core transistor inverters.