Showing papers on "Comparator applications published in 1974"

Variable time delay voltage dropout detector

Abstract: A voltage monitoring system includes a comparator circuit having one input connected to a first reference voltage source and a second input connected through a timing circuit to the voltage to be monitored. An output of the comparator is connected to a set input of a flip-flop having its output connected to a light emitting diode indicator. A second comparator has one input connected to a second reference voltage source and a second input connected through a reset switch to the voltage being monitored. An output of the second comparator is connected to the reset of the flip-flop.

Proximity switch circuit

Abstract: An input terminal is quiescently biased to a voltage closer to the initial threshold setting of a first comparator than to that of a second comparator. In response to the proximity of an object, an alternating voltage is induced on this terminal of an amplitude to actuate only the first comparator. Each time a comparator is actuated, a two state circuit changes the threshold settings of the comparators to bring the one formerly outside of the range of the alternating voltage to within its range and vice versa.

Voltage memory circuit for distribution networks - has VCO in loop with phase comparator comparing supply with oscillator output for signal output continuation

Abstract: The voltage memory circuit for distribution networks avoids frequency deviation problems inherent in networks using resonant circuits to trigger protective cut-out relays by employing a voltage controlled oscillator (1) in a phase tracking loop. The oscillator feeds a phase comparator (2) which compares its output with the network voltage signal (URS) and controls the oscillator frequency via an integrator (3). The oscillator consists of a sawtooth generator and integrator (5). The integrator may contain an operational amplifier (9) whose inverting input and output are bridged by a capacitor (C).

Delta modulation circuitry with automatic squelch and gain control

Abstract: This delta modulating circuit arrangement is fully effective over a wide range of input signals through heavy background noise without periodic adjustment. The modulator circuit comprises an input comparator circuit driving a data-clocked flip-flop circuit that is flipped by a clocking pulse train. The output of the comparator circuit is integrated and applied to a differential amplifier circuit along with a positive or negative current obtained from the complementary output of the flip-flop circuit. The output of the differential amplifier is applied to the input of the comparator circuit. A balancing resistor is shunted across the differential amplifier circuit and adjusted to the mean between performance limits. An automatic gain controlled amplifying circuit is connected between the audio frequency input circuit and the comparator circuit to maintain the signal swing within the capabilities of the delta modulator circuit. Preferably, an optocoupler device is interposed between the amplifying and the comparator circuits for opening the circuit under control of a squelch control circuit to prevent modulating noise in the absence of signal.

Fault detector for igniter testing using high frequency noise

Abstract: A method and apparatus for detecting faults in electrical resistance type igniters, particularly igniters of silicon carbide or the like, employs techniques wherein an operational voltage is applied to the igniter to cause the generation of high frequency noise by a defective igniter. The high frequency noise is passed through a high pass filter and applied to an amplifier, and the amplified noise is presented to a signal level detector in the form of a comparator circuit. The comparator circuit is provided with a reference level to desensitize the comparator circuit with respect to signals other than high frequency noise, and the output of the comparator circuit is received by a memory circuit. The memory circuit, in turn, controls an alarm circuit which emits a signal to indicate a faulty condition of the igniter under test.

Analog signal comparator

Abstract: An analog signal comparator receives a variable potential signal at each of two input ports. The signal at each input port is provided to a gate of one programmable unijunction transistor (PUT) and an anode of another PUT to form mirror-image symmetrical connections to the two PUT's. An output signal from either of the PUT's then indicates the lesser of the potentials at a corresponding one of the input terminals. The comparator is preferably intended for use in a closed-loop motor positioning system.

Voltage controlled oscillator having frequency varying inversely with control voltage

Abstract: A voltage controlled oscillator wherein the frequency of the oscillator varies linearly with the reciprocal of the input voltage. It employs two cascaded operational amplifiers wherein the first functions as a comparator and the second one functions as an integrator, the output of the latter being coupled back to a non-inverting input of the former.

Television tuning system with varactor malfunction detection

Abstract: An all channel television varactor diode tuning system has a presettable counter for deriving the number of the receivable television channel by counting pulses indicative of the tuner local oscillator frequency, which is varied by a voltage ramp circuit under the control of a comparator. The derived channel number is supplied to one input of the comparator, and a channel number selector supplies an encoded desired channel number to the other comparator input and to a frequency band decoder. The band decoder supplies signals to establish appropriate preset counts for the counter in accordance with the frequency band. Malfunction detection circuitry for detecting an improper number of pulses for the presettable counter, when in the low VHF frequency bands, is coupled to the channel number selector and connected through the comparator to force the tuning voltage circuit to drive the varactor in a direction opposite to that indicated by the comparator. This is done by monitoring the tens digit in the counter for occurrence of an 8 or 9.

Catalyst temperature indication using comparator - involves input connected to potentiometer in series with opposite-polarity thermo-element

Abstract: The two input terminals of the comparator are both connected with a potentiometer circuit from which the apparatus collects a comparator voltage. The thermo-element is connected with opposite polarity to that of the comparator voltage and is in series with the comparator and potentiometer. The comparator voltage responds and controls the indicator circuit when the thermo-voltage exceeds a pre-determined value of the comparator voltage. The potentiometer circuit may comprise a first group of resistors and, in series therewith, a number of resistors in parallel whose values are chosen in accordance with the pre-determined comparator voltage.

Frequency and phase comparator

Abstract: A frequency and phase comparator which includes a frequency discriminator and a phase comparator, which is suitable for use in a phase locked loop. The phase comparator produces an output signal proportional to the phase difference between the output signal of a reference oscillator and the output signal of a voltage controlled oscillator when the difference in frequency is within a predetermined range. The frequency discriminator produces a control signal proportional to the frequency difference between the voltage controlled oscillator and reference oscillator, and the control signal is used for increasing or decreasing the frequency of the voltage controlled oscillator.

Circuit arrangement for linearization of the characteristic of a sensor

Abstract: A photovoltaic cell observes a temperature and produces a current which is applied to one input of a precision comparator. The output signal from the comparator is applied to an integrator. There is a feedback loop from the output of the integrator to the other input of the comparator. In this loop the integrator output signal is converted to digital form and then applied to a read-only memory which has stored in it the characteristic of the cell. The output of the read-only memory is converted back to analog form and through a resistor is applied to the input of the comparator. Thus the signal at the output of the integrator, which is taken off through an output buffer amplifier, represents the temperature seen by the cell, with a high degree of accuracy.

Frequency synthesizer with pseudo-reference phase comparator

Abstract: A frequency synthesizer having two feedback control loops, one employing a frequency comparator and the other including a sampling phase comparator. The device is useful in high frequency synthesis of a frequency program such as provided by a digitally programmable frequency divider.

Current comparator for power and energy measurements

Abstract: An instrument for the measurement of energy or power with a high degree of precision. The voltage and current components of the power are determined individually. The voltage component is measured using a precise instrument such as an AC/DC comparator. The current component is measured in a current comparator in which it is balanced against current obtained by applying the voltage component to a high quality resistor and a high quality capacitor. The instrument is especially useful in the calibration of wattmeters and watt-hour meters.

Analog-to-digital converters

Abstract: The analog-to-digital converter comprises a comparator having first and second inputs, and an output. A first switch is capable of connecting a signal to be measured to the first input and a second switch can connect a reference source to said first input. A capacitor is connected between said second input and the reference source and serves to store a charge fed by way of a feed back loop from the output of the comparator. The feed back loop includes current generator means arranged to provide a positive or negative current at the second input until the charge is equalized and change of state occurs at the comparator output. A selector means determines the polarity of the current from the generator means depending upon the state of the output from the comparator. A counter determines the number of counting pulses emitted from a pulse generator during a counting period in which the current generator means is applied to the comparator. After the counting period a settling period occurs where the charge on the capacitor is held and then a discharge period follows in which the capacitor is discharged via the current generator means by means of a current of opposite polarity to that used during the charging period. The measurement cycle thus comprises four periods which include two active and two non-active portions.

Digital line receiver circuit

Abstract: A digital line receiver circuit which incorporates a slope detector in the form of a differential voltage comparator. The two inputs to the comparator receive a composite digital video signal but the signal on the second input is modified by a delay and biasing arrangement such that the output gives a representation of the time positions of polarity changes of the digital input.

Apparatus for generating a synchronization voltage for the ignition pulse control of controlled rectifier-power stages

Abstract: An apparatus for producing a synchronization voltage for the ignition pulse control of a controlled rectifier-power stage from its periodic supply voltage delivered by an autonomous energy supply installation. The inputs of a comparator circuit are electrically coupled via a series connected T-network with the periodic supply voltage. The comparator circuit and the T-network serve to transform the supply voltage into a square wave output alternating-current voltage with predetermined pulse amplitudes and to place the square wave alternating current voltage in phase with the supply voltage. At the output of the comparator circuit there is coupled an RC-element for generating a direct-current average or mean value of the square wave alternating-current voltage. A feedback circuit is provided, the input of which is connected with the capacitor of the RC-element and the output of which is connected with an input of the comparator circuit.

Proximity fuze using Doppler effect with phase comparator

Abstract: The fuze has a function generator (FG) which produces a time-dependent DC output corresp. to the declining missile velocity with any necessary correction. It adjusts a voltage-controlled oscillator (VCC) whose output is applied together with the radial relative velocity Doppler signal to a phase comparator (PD). The VCC supplies the comparison frequency required for the instant of detonation so that the phase comparator triggers the detonation switch when the Doppler frequency attains the comparison value.

High-speed tunnel-diode comparator

Abstract: A high-speed comparator consisting of a tunnel diode and a balanced four-transistor isolating amplifier is proposed. A low-frequency sensitivity of better than 10 mV and a hysteresis of approximately 300 mV were obtained. A maximum operating frequency in excess of 800 MHz was achieved.

Optimal Filters for Binary Detectors with Comparator Hysteresis

Abstract: Methods that increase the speed of digital detection comparators can also produce hysteresis, wherein the effective threshold in a given signaling interval is influenced by the previous output. If the comparator is fed by a peak-limited IF detector output followed by a detection filter with unity dc gain, the hysteresis can be a significant fraction of the peak comparator input. This concise paper derives the detection filter impulse response for which the resulting eye-opening-to-rms-noise ratio is maximized. The impulse response is taken to be either unconstrained in time or confined to a signaling interval (as in filter-and-dump detection). The results for each case are applied to 2- and 4-level coherent phase shift keying (CPSK). Expressions are obtained for the maximized eye-opening-to-rms-noise ratio as a function of comparator hysteresis and phase modulation pulse shape. These expressions are normalized to represent the excess in required power above the theoretical minimum, and graphical results are given. They show the suboptimality of filter-and-dump detection when hysteresis is high, the insensitivity of performance to hysteresis when unconstrained optimal filters are used, and the relative effects of phase modulation pulse shape on required power.