Showing papers on "RC circuit published in 1980"

Switched-capacitor filter design using bilinear element modelling

Abstract: The low sensitivity of a doubly loaded reactance ladder to element-value variations is preserved in a switched-capacitor filter with the same graph if a one-to-one replacement of branch impedances is used to derive the switched filter from the reactance ladder. This paper describes the design principles and some novel circuits based on this approach. The frequency axes of the two filters are mapped into each other by the bilinear s{\leftrightarrow}z transformation; this results in advantageous sensitivity and selectivity properties for the resulting switched-capacitor circuit. In addition, the number of active components is equal to the number of inductors replaced, and is hence small. This results in very economical realization for the integrated filter.

Offset compensating circuit

Abstract: Offset compensating circuit adapted to be built into a circuit to be compensated. The offset compensating circuit (21) is incorporated into a negative feedback loop of the circuit to be compensated, and essentially comprises an integrating circuit. The integrating circuit is composed of switching means (SW) and a switched capacitor-type integrating circuit (23). The switching means (SW) operates to feed either one of a positive reference voltage (+ Vr) and a negative reference voltage (- Vr) in response to the polarity of the output signal from the circuit to be compensated. The positive or negative reference voltage (+ Vr) is applied to the switched capacitor-type integrating circuit (23), which generates an offset compensating voltage (Vc) to be superposed to the input signal of the circuit to be compensated.

Loading apparatus for testing a power supply

Abstract: Loading apparatus for testing a power supply comprises an electronic load circuit, the electronic load circuit comprising an organically and systematically connected mode switching circuit capable switching from and to one another a constant resistance mode, a constant current mode and a slave mode. A load switching circuit is connected to the mode switching circuit and an error amplifier is adapted to input a voltage signal in each of the modes. A field effect transistor circuit is adapted to receive the output of the error amplifier as a gate control signal and has a drain terminal to which is fed the output from a power unit under test and further has a source terminal, the output of which is fed back as a comparison voltage signal to the error amplifier. A current measurement display circuit is branched to the source terminal of the field effect transistor circuit, and an overpower protection warning circuit is also branched to the source terminal. A voltage measurement display circuit is connected to the drain terminal, and a switching time setting circuit is provided for setting an automatic switching time in the load switching circuit.

Active filters with zero transfer function sensitivity with respect to the time constants of operational amplifiers

Abstract: Most second-order RC active filters show a marked dependence on the gain-bandwidth product (GB) of operational amplifiers (OA's) when the \omega_0 to be realized is greater than 1 percent of GB and Q > 10 . Here designs are given that are virtually independent of OA's when \omega_0 GB and Q . Even for \omega_0=0.05 GB and Q=10 , the center frequency shift due to OA's is less than 0.1 percent. This desirable result is achieved by designing filter amplifiers which have zero first-order sensitivities with respect to the time constant \tau = 1/GB of the OA's used in the design. As a result, the filter transfer function has also zero first-order sensitivity with respect to \tau . General criteria for such designs are given. Experimental results show excellent agreement with theory.

Low voltage, low power RC oscillator circuit

Abstract: A resistor-capacitor oscillator circuit (10) is provided and includes a voltage comparator circuit (12). A capacitor (20) is connected to an input terminal (14) of the voltage comparator circuit (12). A resistor divider network (30) is coupled to an input terminal (16) of the voltage comparator circuit (12) for generating a reference voltage. A delay circuit (50, 52) is coupled to an output terminal (42) of the voltage comparator circuit (12). A discharge device (54) is coupled to the delay circuit (50, 52) and to the capacitor (20) for discharging the capacitor (20). A switching device (40) is coupled to the output (42) of the voltage comparator circuit (12) and to the resistor divider network (30) for controlling the application of the reference voltage to voltage comparator circuit (12).

Monolithic hybrid integrated circuits

Abstract: A method of fabricating a thin film semiconductor hybrid circuit is disclosed. After processing of the integrated circuit in the semiconductor wafer up to the point of establishing ohmic contacts (14) to devices (13), a thin film RC circuit is fabricated on an insulating layer (11,12) overlying the wafer. This is accomplished by first forming the capacitor anodes (15') on the insulator by depositing and etching a layer such as alpha tantalum. Resistors (16) are then formed by depositing and etching a layer such as tantalum nitride. Portions of the capacitor anodes are then anodized using an appropriate mask (17) to form the capacitor dielectric. Capacitor counterelectrodes (20') and interconnect conductors (20'") are formed by depositing and etching successive layers of metal such as nickel-chromium and gold. After all thin film components are formed, the resistors and capacitors are stabilized by heating the circuit in an atmosphere comprising high pressure steam.

Apparatus for matching the sound output of a radio receiver to the ambient noise level

Abstract: In a circuit which matches the speaker input signal in a car radio to the then-present noise level, an additional RC circuit is interconnected between the speaker input terminal and the input of the volume control element. Sudden increases in the speaker input voltage following a modulation pause which cause a high increase in the gain of the volume control circuit will counteract this gain, thereby preventing the excessive increase in speaker sound output following such a modulation pause which took place in the known circuits. Zener diodes to limit the voltage at the volume control elements in dependence upon the battery output voltage and to a value such that the output stage driving the speaker will not be overdriven are also provided.

Programmable signal equalizer

Abstract: A programmable signal equalizer uses a plurality of active RC circuits arranged to be controlled by a ladder resistor network. The resistor ladder circuits are selected by digital word signals representative of the selected magnetic tape speed to produce a signal equalization operation at each of the selected tape speeds. A combination of the ladder network circuits is selected by the digital bits in the digital word to form an active RC circuit producing a signal equalization correlated to a selected tape speed. Using an eleven line digital word code and an eleven RC ladder, eight master speed equalizations are selected as well as seven equalizations between the master speeds for a total of sixty-four equalization functions.

Improved circuit elements for switched-capacitor ladder filters

Abstract: A new switched-capacitor floating inductance simulation circuit which does not depend on matching of passive elements is presented. A switched-capacitor source termination circuit which functions as a sample-and-hold circuit for a filter is also described.

A novel active compensation scheme for active-RC filters

Abstract: A novel scheme using two internally compensated operational amplifiers with unmatched gain-bandwidth products is suggested as a replacement for the conventional single-amplifier integrators, inverters or summers. The scheme, while providing exact phase compensation, contributes to magnitude compensation as well. Filters realized using such a scheme have an extended range of frequency of operation with reduced error in pole frequency and in Q.

Protective circuit for output transformer-less circuit

Abstract: A protective circuit for a class B OTL circuit such as a vertical deflection circuit and a sound output circuit of a television set. The protective circuit comprises a first voltage comparator circuit having one input terminal applied with a detection signal in the form of an average voltage of an output signal of the OTL circuit and the other input terminal applied with a first reference voltage, and a second voltage comparator circuit having one input terminal applied with the detection signal and the other input terminal applied with a second reference voltage which is different from the first reference voltage. Either one of the voltage comparator circuits is operated when the output terminal of the OTL circuit is short-circuited to either the power supply voltage line or earth. A control circuit is operated by an output of the voltage comparator circuit to cut off output transistors of the OTL circuit so that the output transistors can be protected from being damaged by large currents due to the short-circuiting.

Method of and circuit arrangement for determining the magnitude of an unknown resistance element

Abstract: In order to ascertain the magnitude Ri of an unknown resistance element in digital terms, two calibrating resistances of known magnitudes R1 and R2 =mR1 (with m>1) are connected in circuit with a capacitor, to form a switchable RC network, during two gating periods whereas the unknown resistance element is inserted in their place during a third gating period. A multiplicity of counting pulses are fed during each gating period to a pulse counter delivering their count to an arithmetic unit which determines the ratio Ri /R1 from the several pulse counts and from the factor m. The switchable RC network may be part of a one-shot pulse generator, establishing a variable gating period for counting pulses of a fixed cadence, or of an astable multivibrator generating different counting pulse rates during gating periods of constant duration. The fixed pulse cadence or the constant gating periods are established by another RC network which may share a common coincidence (AND, NAND or NOR) gate with the switchable network.

Level detection circuit

Abstract: A level detection circuit comprises a peak value detection and holding circuit having a capacitor which detects and holds the peak value of an input signal by charging the capacitor, an operation control circuit for supplying the input signal to the maximum value detection and holding circuit during a specific time interval to perform maximum value detection and holding operation, a discharge circuit which performs constant current discharge of a charged electric charge in the capacitor of the maximum value detection and holding circuit after the specific time interval, and a detection circuit for detecting the level of the input signal by measuring the time interval between a time point the constant current discharge of the capacitor by the discharge circuit is initiated and a time point the terminal voltage of the capacitor reaches a specific voltage.

Pulse counter-type FM detector

Abstract: In a pulse counter-type FM detector circuit for obtaining audio signals at an output terminal by detecting FM signals in the following order through a limiter circuit, a trigger pulse generating circuit, a monostable circuit and an integrator connected to the output terminal where the monostable circuit comprises a gate circuit having at least two inputs where trigger pulses from the trigger pulse generating circuit are applied to a first one of the two inputs and a feedback signal to the other input, a differentiating circuit responsive to the output from the gate circuit, a differential inverter having a power supply and where the integrator includes an LC type low pass filter connected to the output side of the differential inverter circuit, the improvement comprising a terminal resistor connected between the power supply and the output terminal so that a part of the current flowing in the differential inverter circuit is diverted through the terminal resistor.

Analysis of active RC networks by decomposition

Abstract: A method is developed for rapid and intuitive analysis of active RC networks. Only first-order time constants or poles and resistive voltage transfer ratios need be computed, these being calculated with the various capacitors replaced by either shorts- or open-circuits. A computation graph is presented for ordering the calculations.

Switch mode driver

Abstract: A switch mode driver for a wire matrix printer employs a single power switch circuit to connect one or more solenoids across a DC source or power and to disconnect those solenoids from that source. Enable signals are provided to select any one or all of the solenoids, such enable signals remaining for a predetermined time during which a slewing period, followed by a chopping period, occur and after which energy remaining in the selected solenoids is returned to the DC power source. The initial ramping of current through the selected solenoids occurs when the power switch circuit is closed for a time period determined by an RC circuit, such time period defining the slewing period. Then the power switch opens and the chopping period begins. The charge on the capacitor of the RC circuit is discharged and at a certain voltage point, the power switch is again closed until the charge on the capacitor of the RC circuit again reaches a predetermined voltage at which time the power switch opens. This chopping action continues until the enabling signals are disabled. In this preferred embodiment, the time when the power switch is turned on is approximately 1/10 of the chopping period.

Traffic sensor for telephone lines - has evaluating circuit and amplitude limiting threshold value circuit

Abstract: The sensor is intended for traffic monitoring, consisting of analog signals transmitted over telephone lines. It comprises a series connection of an input circuit (1), an amplitude stressing and limiting threshold value circuit (2), and a time dependent signal shaping circuit (3). A second threshold value circuit (4) is provided and a timing circuit (5) which evaluates the pulse and interval periods of signals, transmitted by the second threshold value circuit. The input circuit consists of an amplifier, a low pass filter and a high pass filter. In front of the amplifier may be connected a transformer. A comparator, switchable to different threshold values, may be used as the first threshold value circuit. An integration element may serve as the signal shaping circuit, this element being formed by an RC-element with a charging constant of about 3 ms.

Lock-up type automatic speed change gear

Abstract: PURPOSE:To prevent any idle blow and speed change shock in an engine in such a way that lock-up interrupting time is made consistent with the actual speed change operating time through such arrangement as assigning individually different speed change signal output time to each speed change detecting circuit. CONSTITUTION:Input of signals out of a 1-2 shift switch 60 is given to a two to one speed change detecting circuit 207 and a one to two speed change detecting circuit 208, and input of signals out of a 2-3 shift switch 61 is given to a three to two speed change detecting circuit 218 and to a two to three speed change detecting circuit 219. Besides, output from each speed change detecting circuit is given as input through a NOR gate 217 to an AND gate 228, and further an AND gate 228 is given lock-up permission signals SL as input which is transmitted in response to the operating condition. In addition, since each time constant of the RC circuit in each speed change detecting circuit is individually adjusted, it is set so as to vary the lock-up interrupting time in response to each speed change.

Monolithic v.c.c.s. for high-frequency RC active filters

Abstract: A monolithic voltage-controlled current source designed for the realisation of high-quality RC active filters at frequencies up to 1 MHz is described. The chip is fabricated using standard 741 technology with lateral p-n-p transistors, and requires no internal compensation for stabilisation.

Design of sharp cutoff low-pass maximally flat RC-active filters by cascading third-order blocks

Abstract: Pairs of coincident j{\omega} -axis zeros are added to the multiple real root maximally flat (MURROMAF) approximation function for designing sharp cutoff low-pass RC -active filters. Expressions for transfer function and cutoff slope are derived in terms of the order n , the multiplicity of the real pole \mu , the number of pairs of j{\omega} -axis zeros m and their locations. A design example is also given to illustrate the procedure for finding out the best transfer function.

Tyre-pressure monitoring system for vehicle - has free-running oscillator coupled to evaluator circuit

Abstract: The monitoring system has a free-running oscillator (15) near the wheel being monitored. The oscillator's output is coupled via a capacitor (25) to several parallel indentical RC circuits (26,27) containing grounded capacitors. The connections between the capacitors and the resistors in the RC circuits are coupled to an evaluator (32) and via a line (33) to the grounded induction coil. The capacitor in each RC circuit forces resonant circuit with the induction coil whose frequency is the same as that of the filter (37) and the oscillator. The advantage lies in being able to locate the induction coil away from the main circuitry.

Earth leakage protection devices

Abstract: An earth leakage protection device comprises a core balance current sensing transformer 1 having a secondary winding 2 in which a fault signal is generated in response to leakage from AC supply lines forming primary windings of the transformer 1, an operational amplifier OA1 for amplifying the fault signal, a precision rectifier circuit 8 comprising a pair of operational amplifiers OA2 and OA3 for performing full wave rectification of the amplified fault signal, a delay circuit 9 in the form of a two stage RC network which delays the rectified signal according to an IDMT characteristic, and a trigger circuit 10 in which the delayed signal is compared with a preset reference signal by an operational amplifier OA4 to provide a control signal which actuates a sagety device in the AC supply lines via a relay 11 when the reference signal is exceeded. Within its operating range the device actuates the safety device much more slowly for lower leakage currents than for higher currents, and since it is operative on both halves of the AC leakage current signal the device provides reliable protection against the possibility of dangerous electric shocks while avoiding spurious tripping.

Combining and filter circuit for a phase locked loop

Abstract: A combining and filter circuit is provided to connect the acquisition circuit and phase detector circuit to the voltage controlled oscillator in a phase locked loop. The combining and filter circuit includes twin-T filters for removing reference frequency signals. An output circuit includes series resistors and capacitors, and reverse poled Schottky diodes which provide rapidly changing acquisition signals that are relatively noise free.

Safety device for electric consumers in motor vehicles

Abstract: Safety apparatus for a motor vehicle electric consumer having a temperature-dependent internal resistance, which includes a temperature indicating circuit for providing a signal which accurately indicates the consumer temperature to a threshold switch which actuates a switching device to interrupt current flow through the consumer whenever the consumer temperature exceeds a predetermined maximum value. The temperature indicating circuit either may be a consumer resistance measuring circuit such as a bridge circuit including the consumer in one leg thereof, or may be a consumer temperature replicating circuit, connected in parallel with the consumer, such as a special RC network. The switching device either may be a switch connected in series with the consumer, or a switch connected in parallel with the consumer, in which case the apparatus also includes an overcurrent device connected in series with the parallel combination of the switch and the consumer.

Receive and transmit signal separator for two=wire system - has echo suppression circuit and adjustable balancing network at two to four junction

Abstract: The system separates transmission and reception routes of information transmitted in duplex integral using a two wire link. The circuit uses a two-four wire junction circuit and an echo suppressor connected in a branch circuit between the transmission and reception lines on the four-wire side of the junction circuit. The junction circuit comprises an adjustable equilibrium circuit formed by a passive RC network and a slave circuit.

Simple method for analysis of a class of switched-capacitor filters

Abstract: A simple technique, applicable to most practical switched-capacitor filters (s.c.f.s) is used to model the s.c.f. by an analogue circuit containing only amplifiers, resistors and capacitors with real constant element values. Thus, the s.c.f. response and sensitivities can readily be found using available circuit analysis programs.

Microprocessor controlled safety monitor in motor vehicle - re-runs program to avoid erroneous operation due to parasitic disturbances

Abstract: The program controlled monitoring system, such as a microprocursor system in a motor vehicle, can indicate an apparent failure due to parasitic disturbances. This is resolved by running the program again before operating any safety devices. The microprocessor controlled monitoring system (10) contains a monostable (101) whose inverting output is connected to another monostable (11). A JK bistable (13) acts as a coincidence detector whose output is connected via an OR gate (14) to a safety switch circuit (15). When the monitoring system monostable returns to its original state a short pulse is generated which passes via an RC circuit (18, 19) to a NAND gate (20). This causes the monitoring system to restart its program. An RC tuning circuit (22, 23) is switched from the monitor system to reset the JK bistable.

Device for the monitoring of peak values of a nonperiodic phenomenon with a low recurrence rate

Abstract: Disclosed is a device for the measurement of peak values of a nonperiodic phenomenon having a low recurrence rate. A voltage comparator has one input connected to the potential U e to be measured with its output connected through a rectifying circuit to a parallel RC circuit. The output of the rectifying circuit is also connected to a high input impedance circuit whose output which is indicative of the peak value measured is connected back to the other of the comparators inputs. The time constant of the parallel RC circuit is an inverse function of the error included in the output of the high input impedance circuit during an interval separating two peak values. The invention is particularly useful to indicate very accurately the state of discharge of lead-acid power batteries.

Circuit arrangement to convert digital value into DC signal - has fixed and variable capacitors in AC bridge circuit with rectifiers and differential amplifier

Abstract: The circuit arrangement comprises a capacitative sensor with two capacitors, an oscillator with an inductively coupled output, a rectifier circuit and an alternating current supply circuit. One capacitor (16) has a value which is variable in dependence on the value of the physical quantity and the other (18) has a fixed value. The capacitors are each coupled through a diode (D1, D2) with a secondary winding 22, 24) of the current supply circuit and with a resistor (R1, R2) forming a bridge circuit with diagonal connections to a feedback differential amplifier (38) which is followed later by a second stage amplifier (40).