Showing papers on "Comparator applications published in 1981"

Electronic oscillation counting timer

Abstract: An electronic timer having an oscillator, a counter which counts outputs of the oscillator up to a predetermined count value and thereupon generates an output, and an output circuit for generating an output signal in response to the output from the counter, the oscillator comprising a first terminal for connection with a time constant circuit consisting of a resistor and a capacitor, a second terminal supplied with a reference voltage, a dividing resistance circuit for developing a first upper limit voltage and a lower limit voltage, a first upper limit comparator for comparing a potential at the first terminal with the first upper limit voltage, a second upper limit comparator for comparing the potential at first terminal with the reference voltage, an OR-circuit for receiving outputs from the first and second upper limit comparators, a lower limit comparator for comparing the potential at the first terminal with the lower limit voltage, a flip-flop which is set by an output from the OR-circuit and reset by an output from the lower limit comparator, and a transistor for discharging the capacitor in response to an output generated from the flip-flop.

CMOS Differential comparator with hysteresis

Abstract: A hysteresis circuit is added to a differential comparator to provide a predetermined bias current from one of two input transistors connected in a differential configuration. A current mirror structure is used to accurately determine the amount of current which is shunted when the output of the comparator is in a predetermined state.

Ground circuit voltage detector

Abstract: A ground circuit voltage detector for monitoring stray ground voltages occurring in dairy equipment to provide both an instantaneous warning indication and a sustained alarm indication. The voltage detector is connected between the equipment to be monitored at a sensing input and a separate ground. The sensed voltage is filtered and applied to a first comparator through an averaging circuit. If the average ground voltage exceeds the threshold level of the first comparator, a warning indication is provided which is proportional in strength to the sensed ground voltage. The first comparator is connected in series with a second comparator through an integrator. If the threshold level of the second comparator is exceeded, a sustained alarm indication is provided. A test circuit applies a voltage to the detector input to ensure the detector is operating properly.

Phase-locked loop frequency demodulator and frequency synthesizer

Abstract: A combined phase-locked loop frequency demodulator and frequency synthesizer for frequency-modulated wave receivers using two phase-locked loops respectively for synthesis and for demodulation In this device, the frequency-modulated signal is applied to one of the inputs of a first phase comparator whose other input is coupled to the output of a voltage-controlled oscillator, which output is also coupled, through a prescaler and a programmable frequency divider mounted in cascade, to one of the inputs of a second phase and frequency comparator whose other input is coupled to the output of a crystal-controlled reference oscillator The output of the first comparator is coupled by means of a first low-pass or bandpass filter to a first input of an analog adder whose second input is coupled by means of a second low-pass filter, having a relatively low upper cut-off frequency, to the output of the second comparator The output of the adder which combines the signals from the two filters is connected to the frequency-control input of the voltage-controlled oscillator The output of the first filter supplies the demodulated signal and thus constitutes the output of the frequency demodulator, whose phase-locked loop is combined with the phase-locked loop of the frequency synthesizer, which selects the frequency of the modulated carrier wave, by means of the adder and the single voltage-controlled oscillator which are the common elements of both phase-locked loops

Pulse width modulation amplifier

Abstract: A pulse width modulation amplifier in which interchannel distortion is eliminated by making the pulse transition times different between different ones of the channels. Ramp carrier signals having different phases are applied to respective pulse width modulation comparators of the two channels. The ramp carrier signals are generated by applying the output of an oscillator directly to one of the pulse width modulation comparators while the other is generated through a phase delay circuit which provides constant phase relationship independent of the frequency of the output of the oscillator. The output of the oscillator is coupled to one input of a comparator which produces first and second output signals one of which is in a high state depending upon the relative potentials of the two inputs to the comparator. The outputs are coupled to respective constant current sources which charge and discharge a capacitor in accordance with the output state of the comparator. The output voltage from the capacitor is coupled through an integrator circuit to the second of the input terminals of the comparator.

Direct current fan with control means

Abstract: A network controlled inlet is provided for current sensing in a comparator to control the current in direct current motors. An electrical signal generated from a physical parameter is conducted to the first input of the comparator and a signal characterizing the speed of the motor is conducted to the second inlet of the comparator.

Fume detector and alarm system

Abstract: A fume detector including a gas sensor having a heater element and a variable impedance element associated therewith whose impedance decreases in the presence of toxic gases or fumes, or a decrease of free oxygen in an atmosphere being monitored A load resistor in series circuit with the gas sensor and a pair of series connected potentiometers in parallel circuit with the gas sensor and the load resistor form a Wheatstone bridge A first voltage comparator connected to one of the potentiometers and a reference voltage provides a signal when the supply voltage decreases below a predetermined level A second voltage comparator connected to the other potentiometer and a junction between the gas sensor and the load resistor provides a signal when the gas sensor fails in the open circuit condition A third voltage comparator connected across the bridge provides a signal when a toxic gas condition exists The first, second and third voltage comparator outputs are commonly connected to the input of a fourth voltage comparator A warning device is connected to the output of the fourth voltage comparator and is energized when any one of the signals of the first, second and third voltage comparators falls below a predetermined level

AC Power control circuit

Abstract: An improved control circuit for accurately regulating the power from a supply of unregulated AC voltage to a load, such as a fan motor, via a signal responsive conduction-control switch. The circuit employs first and second comparators. One input to the first comparator is a DC signal representative of desired power level. The other input of the first comparator is a signal having a DC component and a ripple component. The output of the first comparator is a rectangular waveform having a duty factor which is a function of the desired power level relative to the reference load power level. The first comparator output is integrated and then supplied as an input to the second comparator. A sawtooth signal of constant DC level provides the other input to the second comparator. The sawtooth is a submultiple, or preferably a multiple of the AC supply frequency. The output of the second comparator is another rectangular waveform, the duty factor of which is a function of the DC level of the integrated signal and is used to control the conduction timing of the conduction control switch. Preferably, the combined DC-with ripple-signal input of the first comparator is provided by feedback from the second comparator output which is passed through a voltage scaling network connected to an unregulated DC supply. The time constants of the closed loop are selected to provide a temporary power overshoot when increasing the power level. Supplemental limit circuits provide limit signals directly to the second comparator input.

Comparator circuit having hysteresis

Abstract: A high-gain comparator circuit having an upper and lower input offset voltage associated therewith to establish hysteresis in response to a differential input signal supplied thereto. The output level state of the comparator circuit is caused to be switched from a first output level to a second output level in response to the differential input signal exceeding the upper offset voltage only after the hysteresis has been initiated whereby the comparator circuit is less susceptible to being caused to erroneously switch states due to noise transients. The comparator circuit comprises a differential amplifier adapted to receive the differential input signal for producing differential currents in first and second outputs thereof and includes first and second current mirror circuits coupled in parallel to the first and second differential outputs of the differential amplifier which produced the upper and lower input offset voltages in the comparator circuit when respectively activated.

Data regenerative system for nrz mode signals

Abstract: A data regenerative system adapted to receive data signals transmitted with the Non-Return-to-Zero mode comprises a comparator (10) for comparing the voltage level of the received data with a variable threshold to generate a digital comparator output. D-type flip-flops (DFF1, DFF2) are arranged to receive the comparator output to generate first and second pulses respectively in response to a data strobe clock pulse. The time difference between the first and second pulses is detected by a first subtractor (21, 22, 23) to generate an error voltage which is applied to the comparator (10) as its threshold to keep the crossing points of the eye pattern of the received signal aligned on the threshold level. A variable width monostable multivibrator (MM) is responsive to synchronization pulses to generate the data strobe clock pulses with a duration that is a function of an output of a second subtractor (26, 27, 28) representing the difference between each period of the first and second pulses and one-half period of a third pulse generated by a D-type flip-flop (DFF4) in response to the leading edge transition of the output of the monostable multivibrator (MM) in the presence of the first and second pulses. Output pulses are regenerated in response to the output of the monostable multivibrator in the presence of the comparator output.

Frequency and phase controlled HF oscillator - uses frequency divider and phase comparator receiving quartz oscillator reference frequency

Abstract: The high frequency oscillator has a frequency divider (4) with a variable division ratio, supplying a fraction of the oscillator output frequency to a phase comparator (2) for comparison with a reference frequency (Fr). The output of the phase comparator (2) is used to provide a control voltage for frequency regulation of the oscillator. The division ratio of the frequency divider (4) and the momentary value of the control voltage provided by the phase comparator (2) are held and then again released via a control circuit (11), responsive to the two inputs to the comparator (2) being in phase. Pref. the division ratio of the frequency divider (4) is selected by a digital input device (5) which it operates as a counter.

Television receiver high voltage generator protection circuit

Abstract: A high voltage generator of a television display is responsive to an alternating voltage, such as a retrace pulse voltage, for developing an ultor voltage at an ultor terminal. A protection circuit for the high voltage generator includes a comparator that develops a television display disabling signal when activated. A circuit that develops a sense voltage representative of the ultor voltage is coupled to an input terminal of the comparator so as to develop the disabling signal when the ultor voltage exceeds a predetermined level. To provide an overload disabling capability, an ultor beam current sensing circuit is coupled to the input terminal of an operational amplifier. The output terminal of the amplifier is coupled to a bias voltage source and to an input terminal of the comparator. When the ultor beam current exceeds a predetermined level indicative of high voltage generator overload operation, the operational amplifier applies the bias voltage to the comparator input to energize the comparator into developing the disabling signal. The magnitude of the bias voltage is such as to activate the comparator in substantial independence of the value of the ultor voltage sense voltage.

Offset compensation apparatus for biasing an analog comparator

Abstract: A threshold comparator for use with a dual slope A/D converter has its input potential established at its threshold potential during auto-zeroing. Potential offset means is included in the auto-zero feedback loop around the integrating and output amplifiers of the A/D circuit. Bias current applied to the potential offset means substantially tracks current passed in the comparator so that the potential developed by the potential offset means substantially tracks the threshold potential of the comparator.

Analog-to-digital converting apparatus

Abstract: Microprocessor controlled analog-to-digital converting apparatus. For each analog signal input line there is a comparator having one input connected to the associated analog signal input line. A ramp generator is connected in common to the other input of all of the comparators. A multiplexing arrangement is operated by the microprocessor to couple a selected one of the comparators to a storage register in the microprocessor. The selected comparator compares the voltage of the analog input signal to the ramp voltage. If the analog voltage is higher, the comparator output remains inactive and the microprocessor causes a count to be stored in the storage register. The ramp generator is toggled to increase the ramp voltage by a predetermined step. The comparison of the analog voltage and ramp voltage is repeated. If the comparator output remains inactive, another count is accumulated in the storage register and the ramp generator is toggled to increase its voltage by another step. The procedure continues until the ramp voltage exceeds the analog signal voltage and the comparator output becomes active. The microprocessor then causes the multiplexing arrangement to uncouple the selected comparator from the storage register. The accumulated count in the storage register is a digital representation of the analog signal voltage.

Device for disconnecting the receiver in case of a small signal-to-noise ratio for a digital-modulated radio system

Abstract: Rapid disconnection of a receiver in response to a small signal-to-noise ratio is provided in that in the receiver there is arranged a FSK demodulator having two channels connected in parallel at the input ends and each having a band-pass filter, an amplifier and a detector whose output is connected to a voltage comparator. The output signal of the voltage comparator is fed to an input of an AND gate in the receiving arm by way of a series arrangement of a high-pass circuit, a demodulator and a low pass filter to the inverting input of a further comparator whose non-inverting input is connected to a comparison voltage by way of a variable voltage divider. The output of the further comparator is connected to the other input of the AND gate.

Method for eliminating the zero point error in an iterative analog-digital converter

Abstract: A zero equalization capacitor is connected to a first input of the comparator K, and at the beginning of the equalization phase, a voltage value of zero is placed at both comparator inputs, and a feedback network RN is connected between the comparator output and the capacitor, whereby the capacitor is charged to such a degree that the output signal of the comparator arrives at the decision threshold between the equality or inequality of the comparator inputs.

Phase-locked loop oscillator circuit utilizing a sub-loop with a second phase comparator

Abstract: A phase-locked loop oscillator circuit having a reference signal generator, a voltage-controlled oscillator and a phase comparator comprises a second phase comparator. The first phase comparator is supplied with an output of the reference signal generator whose frequency has been lowered and also an output of the voltage-controlled oscillator whose frequency has been lowered. The second phase comparator is supplied with a signal which has been derived from an intermediate position of a higher-frequency path extending from the reference signal generator to the first phase comparator and also a higher-frequency signal which has been derived from an intermediate position of a path extending from the voltage-controlled oscillator to the first phase comparator. Outputs of the first and second phase comparators are added and applied to the voltage-controlled oscillator to reduce residual FM noise.

Masked hysteresis in dual-slope analog-to-digital converter

Abstract: In a dual-slope A/D converter employing hysteresis, a reference voltage circuit sets the threshold of the comparator at three distinct levels in response to a ramp control signal and the comparator output. As a reference capacitor ramps through a threshold voltage, the comparator output shifts the threshold with positive feedback (hysteresis) to provide noise immunity. The ramp control signal then shifts the threshold back to its original level cancelling the hysteresis provided at the first comparator trip point. Thus, the comparator switches at the same voltage for both slopes eliminating offset error.

A/D Converter with bit extension capability using wired-OR outputs

Abstract: A parallel comparator includes a plurality of comparator portions each having first and second transistors differentially connected. The first transistors have their bases connected to receive an analog input signal, whereas the second transistors have their bases connected to receive reference voltages having different levels. Among the plural comparator portions, the collector of the first transistor and the collector of the second transistor are connected with a load in accordance to a predetermined rule. An A/D converter for converting an analog input signal into digital signals of plural codes is also provided which includes a critical detecting comparator for generating a detection output at a predetermined level when the digital signals of the plural codes are converted into such an analog signal as effects the overflow or underflow. The A/D converter includes a control circuit for forcibly controlling the levels of the digital signals of the plural bits in case the detection output of the critical detecting comparator reaches a predetermined level.

Telephone subscriber's line circuit - detects open or closed loop using potential dividers and comparator with threshold switched by controller

Abstract: The condition of a subscriber's line, i.e. loop open or closed, is monitored at an exchange by the potential difference between two potential dividers, one across the line, the other from the b-wire to ground. The potential difference is detected by a comparator whose threshold is set by the central controller to one of three values, depending on whether the transmission bridge is switched to high or low resistance and whether calling signal is being sent. One comparator circuit serves a group of 16 lines via two multiplexers which sample the two potential dividers every 4ms. The comparator threshold is switched by a selector in synchronism with the multiplexers. A hysteresis effect is introduced to prevent hunting in borderline cases, by storing the comparator output in a shift register over one sampling cycle, and using it to offset the threshold.

Closed loop amplitude demodulator

Abstract: An improved substantially "zero distortion" four quadrant modulator of the type including a pair of differential elements respectively coupled to the Y input port terminals of the modulator and exhibiting nonlinear amplitude transfer functions, includes the means for substantially linearizing the nonlinear transfer function. The means includes a pair of operational amplifiers, each having an input coupled to a respective terminal of the Y input port and an output coupled to the corresponding differential element so that the differential element is disposed in the feedback path of the operational amplifier. An improved demodulator is provided by detecting the amplitude modulated signal with a first detector and applying the detected signal to one input of a signal comparator. A feedback loop couples the output of the signal comparator to its other input. In particular the output is coupled to the Y input port of a substantially zero distortion modulator, which has the X input adapted to receive a continuous wave signal. The output of the modulator is detected by a second detector which in turn is coupled to the other input of the signal comparator. The first and second detectors are matched for their nonlinear amplitude transfer functions so that the output of the signal comparator is a substantially zero distorted representation of the envelope component of the amplitude modulated signal.

Starting circuit for electronically controlled motor apparatus

Abstract: A starting circuit for an electronically controlled actuator having an integration capacitor provided in a control signal path and a power supply circuit for supplying a power supply voltage to the motor apparatus, comprises a comparator having first and second given voltages, and a switch circuit coupled to the comparator and to the integration capacitor. The comparator compares the power supply voltage with the first and second given voltages and provides a comparison result when the power supply voltage corresponds to a voltage range between the first and second given voltages. The switch circuit discharges the charge stored in the integration capacitor when the comparison result is provided from the comparator.

Alternating current comparator bridge for resistance measurement

Abstract: TITLE AN ALTERNATING CURRENT COMPARATOR BRIDGE FOR RESISTANCE MEASUREMENT INVENTORS William J.M. Moore Norbert L. Kusters ABSTRACT OF THE DISCLOSURE The ac current comparator bridge measures the resistance of an unknown resistor at 50-60 Hz with an accuracy in the order of 10 parts per million. The current in the unknown resistor is compared, using a current comparator, to the current in a reference resistor for the in-phase component, and to the current in a reference capacitor for the quadrature component or phase defect. Once an ampere-turn balance is achieved in the comparator by adjusting the winding turns, the unknown resistor's values are a function of the reference resistor, the reference capacitor, the voltage sources driving the currents through the unknown resistor and the references, as well as the turns of the windings.

Lighting control interface apparatus

Abstract: An interface apparatus, for remotely controlling a plurality of solenoid actuated switching relays having first and second energizing coils, is capable of providing momentary first and second electrical signals respectively in response to an interruption of an input signal to the apparatus and the initiation of the input signal. The interface apparatus includes a first comparator sensing a change in the input signal, a second comparator sensing a change in the output of the first comparator so as to maintain the second comparator output 180 degrees out of phase with the first comparator output, and first and second monostable multivibrators that each have a trigger input connected to the output of a corresponding comparator so as to generate a momentary electrical signal when the trigger input senses a negative excursion in a change of state at the output of the corresponding comparator. The present interface apparatus has a considerably simplified circuit arrangement which has brought about a considerable cost reduction in the apparatus in addition to an improvement in serviceability therefor.

Tuning device for digital transmitter selection in broadcast receivers, in particular in VHF receivers

Abstract: A tuning device is indicated for digital transmitter selection in broadcast receivers, in particular in VHF receivers which enables a very fast and therefore inaudible changeover between two transmitters. The tuning device has a digital counter which measures the oscillator frequency (actual frequency), an ideal value generator for digital input of the receive frequency (ideal frequency) of a required transmitter, a comparator for the actual-ideal comparison and a device for generating an oscillator tuning voltage depending on the output signal of the comparator. According to the invention, the latter has a successive approximation register whose data input is connected to the output of the comparator and whose parallel outputs are connected to a digital-analog converter. Successive outputs of the register are seized in succession with an output signal, the output signal of the previous output being retained or cancelled before the respective next output is seized depending on the output signal of the comparator. The output signal of the comparator represents sign information for the existing frequency deviation. The analog output voltage of the digital-analog converter forms the control voltage for the oscillator of the broadcast receiver.

Tube output regulation for X=ray test equipment - has comparator peak valve feedback circuit for double comparison with reference

Abstract: The power regulating circuit is for the X-ray tube in X-ray test equipment. The supply uses an inverter (5), high voltage transformer (2), rectifier (3) and storage capacitor (4), to supply the tube (1), with a feedback regulator circuit operating to the peak tube voltage. The feedback regulation is back to the inverter (5) and comprises a circuit for determining the actual peak voltage on the tube for comparison with a reference (12) value. The comparison reference on the output of the comparator (8), feeding into the regulator circuit (10) which outputs to the pulse generator (11) and directly back into the inverter (5), is derived by using the pulse generator (11) to trigger a scanning and storage circuit (15) which finds the peak tube voltage. The actual peak (on 14) is fed into a comparator (13) with a reference (12), through an integrator (16) and then subtracted from the reference (18) so that the input (9) to the second comparator (8) represents the reference regulating potential. The output of the comparator (8) is the compared reference and the actual voltage fed through from the tube (7).

High voltage protection circuit for a television receiver

Abstract: A high voltage generator of a television receiver is responsive to an alternating voltage, such as a retrace pulse voltage, and develops an ultor voltage at an ultor terminal. A high voltage protection circuit includes a comparator that, when activated, disables normal television display. A sense voltage representative of the ultor voltage is coupled to an input terminal of the comparator so as to activate the comparator when the ultor voltage exceeds a predetermined threshold level. A sense voltage representative of the ultor beam current is also coupled to an input terminal of the comparator so as to vary the threshold ultor voltage level at which the comparator is activated in accordance with beam current variations. When the ultor beam current exceeds a level indicative of high voltage generator overload, a switch that is coupled to an input terminal of the comparator changes states to activate the comparator and shut down the high voltage generator.

Resonant circuit measuring inductance - determines frequency of damped oscillations induced via switch using comparator supplied with reference voltage

Abstract: The resonant circuit has its inductance formed by the inductance of a variable being measured and is connected to the non-inverting input of a comparator (8) whose inverting input receives a reference voltage. Damped oscillations are produced in the circuit via a switch (6). The reference voltage is set so that the comparator's output changes state at the end of one half period. The circuit is for use with a microprocessor that closes the switch and receives a signal from the comparator's output at the end of the first half period. The duration of the half period can be used to determine the frequency of oscillation and therefore the value of the inductance (4) being measured.

Circuit for evaluating signals

Abstract: A circuit for evaluating signals has an operational amplifier and a comparator, both of which are supplied by a voltage source connected to ground at one side. The reference inputs of the amplifier and comparator are respectively connected to different taps of a voltage divider also connected across the voltage source, the taps being separated by a low-resistance resistor, thus attaining a stable zero signal level at the signal input of the comparator in the quiescent state through the non-inverting input of the operational amplifier and the output thereof, the stable zero signal level exhibiting a constant voltage difference in comparison to the reference potential at the reference input of the comparator.

Analog signal processing device

Abstract: PURPOSE:To make parts such as a variable resistor unnecessary to improve the reliability of the device, by performing the comparison for the zero level and the span level in a reference voltage and current generator and a comparator adjust A/D and D/A converters by the data processing device. CONSTITUTION:The output terminal of a D/A converter 5 having a data storage circuit 8 is connected to a voltage comparator 6 and an A/D converter 2 having a data storage circuit 7. A data processing device 3 is connected to the input side of the converter 5, and the digital signal from the device 3 is converted to an analog signal. The output of a reference voltage and current generator 1 is applied to the comparator 6, and the output of the generator 1 and the analog output from the converter 5 are compared operated in this comparator 6, and the operation result is applied to the device 3. Until the output signal indicating the coincidence detection is obtained from the comparator 6 in the device 3 in respect to the zero level and the span level, the digital output is fed back and is outputted as correction data to devices 7 and 8. By this constitution, a variable resistance or the like is unnecessary, and the reliability of the processing device is improved.