Showing papers on "Comparator applications published in 1984"

Flow detection apparatus

Abstract: The disclosed flow-detecting apparatus involves gating of phase-related excitation and sensed signals from electrodes close to a flow-activated tracker in a liquid passage. A high gain comparator provides peak-limited signals to the phase-comparison gate. In one form, a pair of excitation electrodes are symmetrical in relation to a single sensing electrode. That electrode supplies a sensed signal to one comparator input, the other comparator input having fixed bias. In another form, a pair of sensing electrodes are disposed in an excitation pattern between a localized excitation electrode and a metal pipe that forms the passage and acts as a second excitation electrode. The sensed signals reach respective input terminals of a high-gain comparator and it responds to the difference between the inputs. Other configurations of the electrodes and their excitation are disclosed, including one that promotes rejection of common-mode spurious signals. A comparator that receives flow-representing signals is stabilized against electrical unbalance by a negative feedback loop having a long time constant. In flow-detection apparatus having a multiple-rotor flow-sensing probe, separate flow-detection circuits are used for the respective rotors. The outputs of the flow-representing circuits are combined. Use of different excitation frequencies for those flow-detection circuits adds assurance of non-interfering operation of the flow-detection circuits.

Electronic circuit for measuring AC electrical energy

Abstract: An improved circuit is provided for a solid state electrical energy meter having a pair of mutual inductance current transducers, a pulse width modulation circuit, an analog switch, and a voltage-to-frequency converter The pulse width modulation circuit includes an integrator having a first operational amplifier with a feedback circuit providing a constant DC gain and a variable gain at the power frequency The pulse width modulation circuit also includes a second operational amplifier configured as a comparator and connected to the first operational amplifier such that the reference level of the comparator is proportional to the average DC output of the first operational amplifier The summing resistors connected to the input of the integrator are of like value and are formed in a common array

Trigger hold circuit for welding power supply

Abstract: A control circuit for an electric arc welder is responsive to the operation of a torch or gun mounted control switch. A first comparator has one input connected to the gun switch and the other input to a reference voltage source. When the gun switch is closed, the output of the comparator will cause a control relay to be energized. When a welding arc is established, a reed switch closes and provides an input to a second comparator which effectively provides a latch to hold the control relay energized. After a predetermined time delay, typically in the order of 1 second, a timer circuit will provide an output to one input of a third comparator, the other input of which is connected to the gun switch. A subsequent closure of the gun switch will caused the output of the third comparator to change the level of the reference voltage, changing the outputs of the first two comparators, thereby removing the latch and deenergizing the control relay. Thus, the control relay can be deenergized either by the welder operating the control switch a second time or by extinguishing the arc, such as by removing the torch from the workpiece; either will disable the latch circuit and terminate the welding operation.

Low offset CMOS comparator circuit

Abstract: A CMOS comparator circuit is disclosed in which a low offset is achieved without trimming. The input stage is composed of a pair of bipolar transistors which have lateral non-dedicated collectors that operate in parallel with the substrate dedicated collectors. The input stage includes matched load devices and is followed by an amplifier having a differential to single ended converter.

Voltage-controlled variable-frequency pulse oscillator

Abstract: The voltage-controlled variable-frequency pulse oscillator in accordance with the present invention comprises an integrating capacitor (50), a variable current source (52) for generating charging current for said integrating capacitor in response to the controlling voltage, a fixed current source (54) for discharging said capacitor, a switching circuit (56) for controlling the discharge of said capacitor, a comparator (58) for outputting a discrimination signal by comparing the voltage of the capacitor and a reference voltage, a dn a multivibrator (60) for receiving the discrimination signal from the comparator and for outputting a pulse signal with a frequency corresponding to the controlling voltage from the variable current source. The multivibrator comprises an R-S flip-flop (64,66) for receiving the discrimination signal output by the comparator at its set side OR-NOR gates, and receiving and for inverting the output of the set side gate which is delayed by a prescribed time to the reset side OR-NOR gate. The R-S flip-flop is constructed to permit the oscillation output with a prescribed frequency to betaken out from the reset side OR-NOR gates, and the oscillation output of the R-S flip-flop controls the drive of the switching circuit. Therefore, the multivibrator starts oscillation on its own within a prescribed width when the capacitor voltage grows very large at the time of turning the power supply on or at the time of generation of an excessively large current where the output of the comparator continues, to stay at a constant value. Furthermore, the current value of the fixed current source is set at more than twice the maximum current value of the variable current source. Because of this, the large voltage of the capacitor decreases gradually with ups and downs, and the comparator inverts after a certain time, the multivibrator discontinues the self oscillation, and the ordinary operation of the device takes place.

Comparator circuit with built in reference

Abstract: A comparator circuit is disclosed wherein the input terminals are provided with a predetermined reference potential. Thus, in the case where only one input is driven the other input is biased at close to the reference. In the application of the circuit it is not necessary to provide an external package pin for reference potential.

Capacitor coupled current mode balance circuit

Abstract: A control circuit is provided for controlling the on-time of a pair of switching transistors in a half bridge converter. The control circuit includes a first comparator for comparing the converter output voltage with a reference voltage. The control circuit also includes a circuit which generates a first signal indicative of the current through the primary winding of the converter output transformer. Also included is a circuit which generates a second signal indicative of the on-time of one of the switching transistors exceeding the on-time of the other switching transistor. The first and second signals are averaged and compared with the output voltage of the first comparator by a second comparator. The second comparator controls the on-time of the switching transistors. In this way, any imbalance in the on-time of the switching transistors is corrected by the control circuit.

Comparator with noise suppression

Abstract: Apparatus for generating a single pulse the first time only that a noisy cyclic signal exceeds a reference level during a half-cycle. For the positive half of a cycle of the noisy cyclic signal, a comparator 12 and a multivibrator 14 produces a fixed voltage output when the noisy cyclic signal first exceeds the reference level. A multivibrator 23 stops the production of the fixed voltage output when the noisy cyclic signal next passes the zero voltage level in the negative direction. Consequently, a single pulse is generated indicating that the signal exceeded the reference level during that half-cycle. Comparator 16 and multivibrator 17 are for producing pulses whenever the noisy cyclic signal exceeds the reference level during the negative half-cycle.

Pulse width modulation type digital to analog converter

Abstract: A DA converter has an N-bit binary counter which counts pulses of a predetermined frequency to generate a plurality of binary numbers within one conversion period. The binary counter supplies an output of lower n significant bits (n-1

Circuit for limiting jitter transients during switching of phase control signals to an oscillator

Abstract: A phase comparator is included with each incoming channel to compare the clock phase of the incoming signal and a local oscillator. The phase comparator of an on-line active unit generates a signal to control the oscillator to maintain its output in phase with the incoming signal. The generated control signal is also connected to capacitor storage in associated channel phase comparators to provide them with an initial starting control voltage when they are switched in to be the receiving channels. Thus eliminating the uncontrolled operation of the oscillator during switching interval.

Low offset single ended MOS comparator

Abstract: A MOS comparator which exhibits a low offset transfer characteristic in spite of parameter variations during production, includes a biasing circuit which causes the transfer characteristics of the comparator stages to track the transfer characteristics of the output amplifier to which it is connected. Offset voltage caused by stage mismatch is thereby eliminated even though the amplifier and comparator are configured differently.

One shot pulse width modulating converter

Abstract: A one shot voltage to pulse width converter is provided for producing a digital representation of an analog input signal voltage The circuit includes an integrating amplifier circuit whose output is kept at a reference potential except when it is being ramped up in response to connection of an input signal to the integrating amplifier during a fixed input sample period or down after the fixed input sample period expires The circuit also includes a comparator connected to compare the output of the integrating amplifier to the reference potential with the output of the comparator switching an output circuit between two different levels so that the pulse width of the output is related to the magnitude of the input signal When the input signal is not connected to the integrating amplifier its output is held at reference potential by a negative feedback from the comparator output to the integrating circuit input

Circuit arrangement for switching on solenoid valves

Abstract: A circuit arrangement for switching on solenoid valves is proposed, which is intended to ensure damped connection of a hydraulic-oil supply to a hydraulic system. For this purpose, a triangular-waveform generator (12) is provided on whose output side a comparator (13) and a switching stage (11) for the solenoid valve (10) are connected, rectangular-waveform pulses occurring at the output of the comparator (13), in time with the voltage of the triangular-waveform generator (12), the pulse width of which rectangular-waveform pulses is dependent on the magnitude of a control signal which is applied to the second input of the comparator (13). A ramp generator (15) for producing the control signal is connected to the second input of the comparator (13) in such a manner that, with the falling edge of the control signal, the width of the rectangular-waveform pulses at the output of the comparator (13) increases up to 100% of the cycle duration of the triangular-waveform generator (12) and hence causes the solenoid valve (10) to switch on gradually.

Oscillator synchronizing system for eliminating static phase errors

Abstract: Non-inverting amplifier, with bandpass filter in regenerative feedback path, forms color reference oscillator in a color TV receiver. Phase shift circuit, responsive to an oscillator output, supplies signals to a first phase shifted signal amplifier, which shares a load with the non-inverting amplifier, and is subject to control by complementary outputs of a phase comparator functioning to compare the phase of an oscillator output with the phase of incoming color synchronizing bursts. A voltage comparator, responsive to the respective phase comparator outputs, is periodically enabled by field rate keying pulses. The voltage comparator output controls the charging or discharging of a capacitor during the keying intervals. A second phase shifted signal amplifier, responsive to the output of the phase shift circuit, and delivering its output to the oscillator's feedback path, is subject to control in dependence upon a comparison of a control voltage derived from the voltage held by the capacitor with a reference DC voltage.

Power line locked image processing systems

Abstract: A line locking system for use with X-ray video imaging equipment comprising: a system oscillator, a divider for frequency dividing the output of the system oscillator to obtain a signal having a frequency that is an integer multiple of the line frequency, a comparator for comparing the phase of the integer multiple signal to the phase of the line signal and means for controlling the oscillator frequency responsive to the output of the comparator.

Digital video special effects generator

Abstract: Keying signals controlling the switching from a first to a second available signal source are available at the output of a comparator. The input of the comparator receives the output of a presettable up/down counter. The comparator has a first reference input which receives a first reference count (generally one half of the maximum count) at which the counter is switched from up to down operation. The second reference input receives a clip reference count which is less than the first reference count. If the oscillator oscillates at a frequency which is a predetermined multiple of the line frequency, and if the counter is reset at the line frequency, the keying signal will cause a vertical bar containing the picture information from the second signal source to appear within the remaining display which corresponds to the first signal source. The position of the bar can be varied by changing the preset input of the main counter, while its width can be varied by changing the clip reference. Squares can be generated by combining keying signals derived from horizontally synchronized and vertically synchronized apparatus of the above described type in an AND circuit. Many other shapes can be generated by changing the preset inputs and/or the clip reference input of either or both the horizontally and vertically synchronized apparatus. Basic shapes other than bars can be created by use of other inputs to the comparator (e.g. ramps) in conjunction with other comparator settings.

Novel tracking amplifier composed of switch and comparator

Abstract: A new amplifier (called a tracking amplifier) is proposed which need not contain any amplifying elements such as transistors and valves. It is composed of a switch, a comparator, a voltage divider and a low-pass filter. On a principle similar to delta modulation, the input signal is compared with a part of the output signal obtained through feedback. The source voltage is switched with the comparator output, and smoothed, so the amplifier output varies in proportion to the input signal.

Phase comparator for a digital phase locked loop

Abstract: The comparator compares a received digital data signal (f1) at each transition of a reference clock (fo). The comparator comprises a first D flip-flop (137) for comparing the data signal with the leading edge of the reference clock, a second D flip-flop (147) for comparison with the trailing edge of the clock, a third D flip-flop (139) for delaying the phase comparison signals and four D flip-flops (141, 143, 145, 149) for storing the comparison signals until receipt of an external reset signal obtained from logic gates (155, 157). The comparator further comprises two OR gates (151,153) giving an output when a positive respectively a negative phase adjustement is required.

Recovery system for a control loop

Abstract: Non-inverting amplifier, with bandpass filter in regenerative feedback path, forms color reference oscillator in a color TV receiver. Phase shift circuit, responsive to an oscillator output, supplies signals to a first phase shifted signal amplifier, which shares a load with the non-inverting amplifier, and is subject to control by complementary outputs of a phase comparator functioning to compare the phase of an oscillator output with the phase of incoming color synchronizing bursts. A voltage comparator, responsive to the respective phase comparator outputs, is periodically enabled by field rate keying pulses. The voltage comparator output controls the charging or discharging of a capacitor during the keying intervals. A second phase shifted signal amplifier, responsive to the output of the phase shift circuit, and delivering its output to the oscillator's feedback path, is subject to control in dependence upon a comparison of a control voltage derived from the voltage held by the capacitor with a reference DC voltage. A latching circuit, subject to disabling only when receiver's color killer circuit operates in a color unkilling mode, is switched into a first latched mode of operation if voltage held by capacitor reaches a first extreme of its variation range, said first latched mode of operation forcing an unbalance of a first sense upon the voltage comparator inputs. Latching circuit is switched into a second latched mode of operation, forcing an opposite sense unbalance upon the voltage comparator inputs, if voltage held by capacitor reaches opposite extreme of its variation range.

Voltage comparing circuit

Abstract: PURPOSE: To prevent oscillations due to noise and to perform stable comparing operation by equipping a voltage comparator with a feedback capacitor. CONSTITUTION: A reference and a signal voltage are applied to the uninverted and inverted input terminals of the voltage comparator 1, which generates an output of H or L according to whether the signal voltage is higher or lower than the reference voltage. This comparison output is fed back to the univerted input terminal side through the capacitor 7 to prevent oscillations due to noise in the output of the comparator 1, performing stable voltage comparing operation. COPYRIGHT: (C)1985,JPO&Japio

Circuit arrangement for determining and displaying that a luminous intensity limiting state has been exceeded

Abstract: In the case of a circuit arrangement for determining and displaying that a luminous intensity limiting state has been exceeded, in the case of which circuit arrangement a comparator compares a temperature-dependent measurement, which is obtained by taking the logarithm of a photocurrent with a limiting value which can be defined and contains an adjustable temperature dependency, the comparator is connected by means of one input, in a manner known per se, to the output of a logarithmic amplifier, and by means of its other input to the pick-off of a potentiometer Furthermore, for its part, the potentiometer is connected therein to a temperature-dependent divider circuit, and the output of the comparator acts on a display circuit and/or a processing stage

Bootstrap power regulator for systems such as analog to digital converters

Abstract: A circuit for supplying two regulated supply voltages to the amplifier/comparator (40) of a recirculation of remainder analog to digital converter, comprises a series pair of transistors (84,86) connected as emitter followers. Outputs of the emitter followers (84,86) are applied to the supply terminals of the amplifier/comparator (40). The junction voltage as input between two Zener diodes (76,78) is controlled by a difference amplifier (66). The output of the difference amplifier (66) causes the regulated supply voltages to track a common mode signal component. Another pair of Zener diodes (72,73) between the output of the amplifier/comparator (40) and the input to the difference amplifier (66) prevents saturation of the amplifier/comparator (40).

Light intensity sensor providing a variable output current

Abstract: A light intensity sensor includes a variable-voltage opto-electronic generator adapted to deliver to the terminals of a load resistor a voltage varying as a function of the variable light intensity detected by the sensor. A reference voltage generator is connected in series to the non-inverting input terminal of an electronic voltage comparator. One terninal of the opto-electronic generator, which is also and output terminal of the sensor, is connected via a loop resistor to the inverting input terminal of the electronic voltage comparator. The output terminal of the comparator is connected to the input terminal of a current amplifier fed from an external voltage source via the other output terminal of the sensor. The output of this amplifier is connected to the inverting input terminal of the electronic voltage comparator. The sensor provides an output current that varies as a function of the variable voltage generated by the variable-voltage opto-electronic generator.