Showing papers on "Relaxation oscillator published in 1971"

LSA relaxation oscillator principles

Abstract: Oversized n-GaAs diodes operating in the LSA mode with doping-to-frequency ratios in the 1-5×105s/cm3range are investigated in circuits that contain a short-circuited high impedance transmission line foreshortened to resonate the electronic parallel capacitance of the diode. By comparing computer simulations with experiments, such diodes are shown to operate in a nonsinusoidal LSA relaxation mode which offers good efficiency, effective space-charge control, and a fast buildup of the oscillations; details of the computer program are also given. A simple analysis is developed which defines the inductive and capacitive time constants controlling the voltage waveshape and explains the frequency tuning with bias voltage and the effective space-charge control. The analysis is shown to be suitable for oscillator design purposes.

Coating apparatus control with delay-duration timer having constant current charging circuit and bistable trigger circuit

Abstract: A control system for turning on and off an apparatus which discharges a coating liquid onto objects at a coating station. A sensor positioned adjacent the path of the objects upstream of the coating station initiates an interval timer as an object passes. After a predetermined time delay, the timer turns on a discharge gun positioned at the coating station, to begin to deposit the liquid upon the object. The timer maintains the discharge gun in an actuated condition for a predetermined time duration, and then turns the gun off. The control provides rapid and reliable turn on and turn off of the coating apparatus without false triggering, and provides precise time intervals which are continuously settable over an exceptionally wide range. The control utilizes a rapid reset hold and lock out circuit, SCR switches, unijunction relaxation oscillators having constant current charging circuits, an over voltage output circuit with short circuit protection, and means for programming the operation of plural discharge devices over different time periods.

Electronic flashlamp power supply

Abstract: A flash system power supply for charging a storage capacitor employed in operating a flashlamp. A battery-powered multivibrator-type converter is coupled to the storage capacitor through a transformer-rectifier circuit, with the multivibrator being triggered into oscillation by a start circuit comprising a relaxation oscillator. Multivibrator operation is squelched by a negative voltage pulse from a stop circuit controlled by a relaxation oscillator-type voltage detector which senses a predetermined charge on the storage capacitor. The stop circuit is also controlled by a current-sensing resistor which detects discharge of the storage capacitor. Operation of the start circuit is clamped to the stop circuit through a diode, with the stop circuit having a time constant sufficient to delay restarting of the multivibrator beyond the deionization period of the flashlamp.

A fail-safe electronic comparator circuit

Abstract: This disclosure relates to a fail-safe comparator circuit having a free-running multivibrator powered by two separate d.c. supply voltages. A resonant circuit is coupled to the output of the multivibrator and tuned to the normal resonant frequency of oscillation of the multivibrator so that oscillations having the normally resonant frequency will be induced into the resonant circuit when and only when the two d.c. supply voltages are in agreement and no critical component or circuit failure is present.

Phased locked loop with voltage controlled oscillator

Abstract: Phase locked loop having a voltage controlled oscillator, a phase comparator and filtering means all of which are integrated into a single monolithic block The comparator is of The balanced bipolar analog multiplier type and is supplied a control voltage by a multivibrator of the voltage controlled oscillator The collector load of the multivibrator is provided by the diode drops of the comparator's transistors The multivibrator is driven by a differential current divider which in turn is provided current by a constant common current source

Voltage-controlled oscillator using complementary symmetry mosfet devices

Abstract: A voltage-controlled oscillator that is compatible with integrated circuit techniques and comprises complementary symmetry MOSFET devices to provide linear operation over several frequency decades, and exhibits high input impedance and minimum power consumption. The frequency of operation is controlled by a current source which is controlled solely by an input voltage. The constant current source linearly charges a capacitor through a bridge circuit. The bridge circuit which includes two complementary MOSFET transistors in each arm is connected across the current source and arranged so that when one transistor in an arm switches on the diagonally opposite transistor, in the other arm, also switches on. The rising voltage across the capacitor is used to change the state of a bistable multivibrator when a given threshold voltage is reached. The output of the bistable multivibrator discharges the capacitor, causes the capacitor to be charged in the opposite direction and provides an output terminal for the voltage-controlled oscillator.

Adjustable pulse train generator

Abstract: A compact simplified pulse generator for generating a train of accurately timed pulses. The timing or spacing between pulses can be adjusted as desired. This is accomplished using a single comparator and a single monostable multivibrator with a digitally controlled reference voltage generator.

Stabilized multivibrator circuit

Abstract: An integrated circuit multivibrator provides a stable time constant under varying ambient temperature conditions and with varying supply voltages by commutating a timing capacitor of the multivibrator between matched current source charging circuits. A gating circuit is coupled to the junctions of the timing capacitor with the current sources and supplies an output to a comparator circuit which provides the output pulses from the multivibrator. An astable or free running multivibrator also can be formed with the addition of a bistable circuit to the basic circuit.

Control signal generator with selectively switchable duration control circuit

Abstract: A transmitter for producing control signals of precisely predetermined duration, for example, for remote control of a television receiver or other apparatus, has an oscillator operable to generate a signal, a switching transistor operable to connect the oscillator with an operating voltage source, and a switching assembly selectively operable to cause operation of the switching transistor and also to determine the charging time constant of a charging circuit by which the period of operation of the oscillator is controlled.

LSA relaxation oscillations in a waveguide iris circuit

Abstract: Large-signal computer simulations of GaAs LSA relaxation oscillations in an X-band waveguide iris circuit are presented. The study is focused on a particular oscillator and a realistic model of an experimental circuit is used. However, the results are typical for other LSA relaxation oscillators. Basic features of the microwave circuit, characteristic voltage and current waveshapes, frequency tuning with bias voltage, and oscillator starting transients are discussed. The RF output power is shown to build up in less than ten cycles. Circuit optimization for high dc to RF conversion efficiency is discussed and circuit data for nearly 30 percent efficiency are given. Finally, efficiency degradation is discussed when doping gradients are present, and effciencies of 15 and 10 percent appear possible for doping gradients as high as 20 and 60 percent, respectively. Hence, the LSA relaxation mode is shown to be less sensitive to doping gradients than the sinusoidal LSA mode.

Amplitude stabilized complementary transistor oscillator

Abstract: Part of the output of a push pull Clapp oscillator is rectified and smoothed to provide a voltage for stabilizing the oscillation amplitude, the control voltage being fed to the base of a transistor that acts as a variable resistance in a voltage divider connected to the bases of the push pull oscillator transistors, the controlled conduction of the voltage divider transistor acting to control the working points of the oscillator transistors so as to maintain a substantially constant oscillation amplitude.

Disabling circuit having a predetermined disabling interval

Abstract: A disabling circuit having an integrator-threshold device, a pulse generator such as a monostable multivibrator and a shaper for delivering an output pulse to a load. A feedback path including a semiconductive switch element from the output of the multivibrator to the integrator-threshold device inhibits operation of the integrator for a predetermined time interval determined by the duration of the multivibrator pulse. The monostable multivibrator includes semiconductive circuitry which draws no power in the OFF condition and further includes a FET to insure rapid transition from the ON mode to the OFF mode of operation.

Horizontal oscillator disabling circuit control apparatus

Abstract: Concurrently filed United States Patent application Ser. No. 144,457, entitled ''''HORIZONTAL OSCILLATOR DISABLING CIRCUIT'''' describes a means of shifting the frequency of the horizontal oscillator of a television receiver in the presence of high voltage increases which could cause X-radiation problems. As therein described, a negative direct voltage indicative of the developed ultor potential for its cathode-ray tube is combined with a relatively stable positive direct voltage to change the bias on a control transistor and the effective resistance in the time constant network determining the oscillator frequency. The present invention provides a further positive direct voltage to the transistor from the brightness control network of the receiver, so as to control the point at which the oscillator goes off frequency as a function of picture tube beam current. Such further voltage will be seen to reduce the criticality in determining the point at which the frequency shifting is to occur and the point at which the reproduced picture becomes unviewable.

Synchronized trigger generators for use with a switching regulator

Abstract: A JK flip-flop provides signals to alternately trigger first and second transistor blocking oscillators which supply trigger signals for a switching regulator Each of the blocking oscillators uses a capacitor between the transistor base and ground to reduce the effects of noise signals and uses an inductor in the transistor emitter circuit to prevent high frequency oscillations

Timing circuit with multiple time constants and switching means to connect and disconnect said time constants selectively

Abstract: A circuit utilizing a unijunction transistor or equivalent relaxation oscillator with a flip flop connected to the output thereof and having its output connected to control the time constant of the relaxation oscillator so that on alternate oscillations the time constant will be relatively low and on the remaining oscillations it will be relatively high to generate a signal having two time intervals in succession. A logic network controls driving circuits in response to the signals produced by the oscillator and the logic circuit divides the frequency of the oscillations to values suitable for timers such as interrupter timers for telephone systems.

Signal controlled wide range relaxation oscillator apparatus

Abstract: A wide range oscillator which can operate over approximately a 104 frequency range. The oscillator uses a current controlled ramp generator which varies the charging rate of an integrating capacitor. The wide range of charging current plus a low discharge time of the integrating capacitor combines to enable a very wide frequency range oscillator.

Speed control system for alternating current induction motors

Abstract: A speed control system for alternating current induction motors wherein a reference potential, which is a rectified phase of the alternating current supply potential, is connected across the series combination of a variable resistor and the timing capacitor of a unijunction transistor type relaxation oscillator circuit and a direct current control potential, which is a function of motor speed and which may be selectively varied in magnitude to change the speed of the motor, is connected across the variable resistor in the same polarity relationship as the reference potential. The unijunction transistor type relaxation oscillator circuit and associated circuitry produces a trigger signal at the electrical angle of each potential cycle of each phase of the alternating current supply potential as determined by the difference of magnitude between the reference and control potentials which trigger respective silicon controlled rectifiers conductive to complete an energizing circuit for the corresponding phase winding or the motor. Another capacitor, connected across the series combination of the variable resistor and the timing capacitor, establishes the difference of magnitude between the reference and control potentials at substantially zero upon motor start and increases the difference at a predetermined rate to a maximum as determined by the selected magnitude of the control potential.

Horizontal oscillator disabling

Abstract: Pending U.S. Pat. Applications Ser. Nos. 103,713 and 121,250 disclose high voltage protection circuits which change the frequency of the horizontal oscillator of a television receiver in response to an indication of increase in the ultor potential developed for its picture tube which could cause danger of X-radiation. Whereas the circuits of such disclosures operate to change a voltage in the horizontal oscillator to which a capacitor is required to charge in establishing the oscillator frequency, the circuit of the instant invention operates to vary a resistance which, together with a capacitor of this type, sets the time constant which determines such frequency.

Experimental observations of relaxation oscillator waveforms in GaAs from less than transit-time frequency to several times transit-time frequency

Abstract: The purpose of this letter is to show that almost all microwave oscillations seen in GaAs, at all frequencies, can be completely accounted for by accumulation layer mode (LSA) operation of the device and therefore only dependent on the current peak-to-valley ratio and the circuit characteristics. The electric field and space charge configurations inside the device must be considered only when they may result in avalanche breakdown. This is true for oscillations even at or below the "transit" frequency.

Voltage controlled oscillator

Abstract: A self-starting voltage controlled oscillator having a frequency which is a linear function of its control voltage and which uses two identical trigger circuits with a single capacitor connecting an input terminal of each trigger circuit to an input terminal of the other trigger circuit. Each trigger circuit may be a bistable Schmitt trigger. A pair of feedback loops connect the outputs from each trigger to its input. The other output from each trigger circuit controls a switch to change the capacitor charging signal path as the states of the triggers change. The frequency of the oscillator is also a linear function of the capacitor value or of the resistor connected between the control voltage and the switch. The oscillator may be used in a phase lock loop circuit to lock on to and control the frequency and phase of an incoming signal from a read head used with a magnetic recording apparatus. It may also be used in any application where a controllable oscillator is required.

Pulsed power supply system

Abstract: A DC source is coupled into a unijunction transistor relaxation oscillator with the output of the oscillator driving the gate of an SCR. The voltage pulse appearing on the anode of the SCR is transformer coupled into a voltage multiplier circuit, the output of which is connected between the ion source anode and cathode of an accelerator tube used for producing fast neutrons from the D-T reaction. Because SCR''s are subject to latch-up, the circuit also has a transistor connected between the cathode of the SCR and ground with the base of the transistor being transformer coupled through a capacitor back to the anode of the SCR. As long as the SCR is operating normally, a portion of the negative pulse developed on the SCR anode is inverted and coupled to the base of the transistor, thus turning the transistor on and allowing the SCR current to flow to ground through the very small saturation resistance of the transistor. In the event of latch-up, the SCR no longer produces pulses, thereby removing the drive from the transistor leaving the transistor in a non-conducting state. Thus, a high impedance is presented between the cathode of the SCR and ground. The SCR will then recover to its non-conducting state. There is sufficient impedance on the SCR cathode, however, that it will try to turn on again from the gate drive supplied by the unijunction relaxation oscillator and thus a pulse will be produced to drive the transistor into conduction and the circuit will begin to operate in a normal mode.

A switching lateral transistor

Abstract: A switching phenomenon has been reported in certain lateral geometry transistors in silicon integrated circuits. These devices switch between conducting and nonconducting states at a critical value of V CE . A hypothesis for the mechanism has been proposed. In this paper an equivalent circuit is developed for the switching lateral transistor and is used to predict transistor behavior. The effect of manufacturing tolerances on the device switching voltage is investigated and a technique of production control is proposed. Circuits using the device are described in which the circuit switching voltage may be varied over a wide range. Some applications of the switching lateral transistor, as an overvoltage protection circuit and a relaxation oscillator, are described.

System for regulating the supply of electrical power to a load from an a.c. source

Abstract: 1,240,912. Automatic temperature control. AZTEC INDUSTRIES Inc. June 23, 1969, No. 31564/69. Heading G3R. An automatic temperature control system comprises a heating element fed from an A. C. supply by way of a switching device, the arrangement being such that the switching device is operative to connect the heating element to the supply only at times when the supply voltage is zero. A heating element 36 is fed from an A. C. supply 10, 14 by way of a bridge of rectifiers across which is connected a thyristor SCR2, the element 36 being energized when a gating signal for the thyristor SCR2 is present on a conductor 32. A stabilized control voltage is developed on conductors 12, 22 from an A.C. source 12, 14, for feeding the control parts of the system. A potential devider R2, P1, P2, P3 is connected across the lines 12, 22 a switch SW1 being included to select potentiometer P1 or P2; the potentiometer P1 being controllable to set the desired day time temperature of the system and the potentiometer P2 the night time setting. The switch SW1 may be manually or time controlled. A thermistor 26, sensitive to the heating element 36 provides a variable bias to the base of transistor Q1, thereby, by way of transistors Q2, Q3, to provide a signal at the emitter of unijunction transistor UJT1. This transistor forms, together with capacitor C2, a relaxation oscillator, which triggers a thyristor SCR1 forming part of a memory device. When thyristor SCR1 is turned on, a capacitor C4 discharges and the voltage at a junction 30 drops to zero, this voltage being applied to the base of a transistor Q4 forming part of a NAND gate. When the voltage of the A.C. source passes through zero the voltage on the base of the other transistor Q5 of the NAND gate is also zero. An output then appears at a point 34 of the gate which triggers the thyristor SCR2 to energize the heating element 36. The bridge of rectifiers may be replaced by a pair of reverse parallel connected thyristors or the load 36 may be placed in parallel with the thyristor SCR2 so as to be energized with D. C. In another embodiment the load is arranged to be energized either between terminals 10, 12, or 12, 14.

Ignition circuits for high pressure mercury lamps

Abstract: 1,254,892. Central systems for operating high pressure mercury lamps. HONEYWELL Inc. 17 Jan., 1969 [20 Jan., 1968], No. 2810/69. Heading H2H. A control means for operating a high pressure mercury lamp comprises means whereby starting pulses are repeatedly applied to the lamp for ignition thereof during such times as the lamp is not ignited. A high pressure mercury vapour lamp QL is supplied from an A.C. source 1-4 by way of a transformer T1 and a rectifier bridge GB, the output of which is smoothed by capacitors C1-C3, the normal running current for the lamp passing through the secondary winding L2 of a transformer T2. The primary winding L1 of this transformer is connectedwhen a thyristor Q1 is made conductive-to a voltage doubling circuit CR3, CR4, C5, C6, R9, R10 which is supplied from a secondary winding on the transformer T1. Control of the thyristor Q1 is by way of a relaxation oscillator circuit comprising a unijunction transistor Q2. A voltage proportional to that across the lamp QL is taken from a voltage divider R5, R6 and applied to the emitter of the transistor Q2. The voltage applied to the bases of the transistor Q2 is derived from a voltage divider R2, R3. When the lamp is not ignited the voltage across the lamp is high and causes oscillation of the oscillatory circuit such that triggering pulses are applied to the thyristor Ql and hence ignition pulses are repeatedly applied to the lamp QL. When the lamp ignites, the voltage thereacross falls to a value incapable of sustaining the oscillations and thus terminating the generation of ignition pulses for the lamp.

Light source power supply

Abstract: 1,270,480. Lamp starting; voltage multipliers. CONSOLIDATED INTERNATIONAL CORP. 6 May, 1970, No. 21734/70. Headings H2F and H2H. A circuit for starting a xenon lamp comprises a non-inductive voltage multiplier 44, and a starting circuit 24. The starting circuit comprises a relaxation oscillator, consisting of a Shockley diode 92, and capacitor 90 which applies a series of pulses to the trigger electrode of a thyristor 82. When capacitor 78 has charged, the biasing on the thyristor 82 is such that it becomes conducting on receipt of a pulse on line 84. This causes a pulse in the primary of pulse transformer 80 which causes a trigger pulse on electrode 26. The voltage multiplier circuit 44 maintains a voltage across the lamp terminals sufficient to start the lamp when a trigger pulse is incident at electrode 26. The voltage multiplier operates by successively charging capacitors 68, and 70, and then successively charging capacitors 72 and 74, so that at each stage a doubling of the voltage incident on lines 21 and 20 is achieved. Thus the voltage multiplier in effect quadruples the voltage. When the lamp 12 conducts and draws current, the voltage multiplier ceases to act as a multiplier and operates merely as a full wave rectifier bridge. When this occurs the output of lines 28 and 29 to the trigger pulse generator drops to substantially zero. Thus rendering the trigger pulse circuit inoperative once the lamp has been struck. Two lamps may be run off the circuit, connected in series, instead of a single lamp.

Unijunction transistor relaxation oscillator with rapid capacitor discharge circuit

Abstract: The shape of the output pulses from a unijunction transistor relaxation oscillator is improved by a circuit which rapidly discharges the capacitor of the oscillator. The discharge circuit is actuated by a monostable multivibrator, the input of which is connected to the output of the oscillator.