Showing papers on "RC circuit published in 1977"

FILSYN—A general purpose filter synthesis program

Abstract: A very general computer program is described that can be used for the synthesis of passive LC, active RC, and (infinite impulse response) digital filters. Although it operates in both batch and interactive modes, this discussion deals exclusively with the interactive mode, which is somewhat more general and very easy to use. Apart from offering superior accuracy and flexibility, this program offers many firsts, including the passive realization of complex quadruplets of transmission zeros, the simultaneous realization of two transmission zero pairs, the active RC leapfrog realization, and many others.

Intermodulation antiinterference device for superheterodyne receiver

Abstract: An intermodulation antiinterference circuit for a superheterodyne receiver having a receiving antenna comprising a first high frequency amplifying circuit responsive to the receiving antenna; a local oscillating circuit; a first frequency conversion circuit responsive to the first high frequency amplifying circuit and the local oscillating circuit; a variable attenuation circuit disposed between the receiving antenna and the first frequency conversion circuit; a nonlinear circuit responsive to the receiving antenna having less linearity than the first high frequency amplifying circuit; a second frequency conversion circuit responsive to the local oscillating circuit and the nonlinear circuit; a comparison circuit responsive to the first and second frequency conversion circuits for generating an output when the output of the second frequency conversion circuit is greater than the output of the first frequency conversion circuit; and means for changing the attenuation of the attenuating circuit.

Optimum design of linear tuning algorithms

Abstract: A high-performance RC active filter realized as a thick or thin-film hybrid integrated circuit presents special fabrication problems. A filter of this type is so sensitive to its parameters that in a large proportion of cases, a circuit so constructed will not meet its performance specifications even if the tightest practicable tolerances are held on the circuit components. As a consequence, the filter network must be tuned after fabrication. It is not feasible to adjust circuit capacitors, hence all tuning must be accomplished by resistor adjustment, and these adjustments can only increase resistance. In this paper, a generalized tuning technique is described which makes the design of a tuning algorithm, and automated tuning, amenable to a universal computer mechanization. In addition to eliminating the analysis and software preparation required to set up a process-control system, the generalized algorithm improves the yield and speed of operation of the tuning process. The central idea of this tuning scheme is to estimate transfer function coefficient errors based on capacitor measurements and then to choose resistance values for the circuit in such a way as to minimize these errors. The operation of the algorithm is sequential, with succeeding resistance values chosen to minimize the cumulative error due to preceeding process steps.

Crystal overtone oscillator using cascade connected transistors

Abstract: An overtone oscillator of the feedback type is provided by a transistor, a crystal resonant at a fundamental frequency and higher odd overtone frequencies, and a feedback circuit that includes the crystal, a second transistor connected in cascade with the first transistor and an RC network. This feedback circuit provides the correct phase shift to achieve and sustain oscillations at the desired overtone frequency.

Tone control circuit

Abstract: A tone control circuit for stereophonic amplifiers, guitar amplifiers and the like is disclosed. The tone control circuit includes a bass circuit having a first variable resistor whose movable contact is connected to an output terminal of an amplifier circuit, two resistors equal in resistance connected respectively to two end terminals of the variable resistor, and a capacitor shunting the variable resistor. The tone control circuit also includes a treble circuit having a second variable resistor, a resistor, and a capacitor. The treble circuit is connected in parallel to the bass circuit in such a manner that the gain in a particular frequency range of the amplifier circuit can be changed by varying the resistances of the two variable resistors.

Circuit for interfacing between an external signal and control apparatus

Abstract: An input/output interface for a digital controller including an optical isolator coupling an input portion which formats an external signal to make it compatible with the optical isolator and an output portion comprising an RC network connected to a threshold detector with hysteresis to provide a filtered output logic signal in addition to an accompanying audio or visual signal. The interface, with slight modifications can be used with either DC or AC external signals.

Protection circuit for transistorized switch

Abstract: The collector-emitter voltages (V ce ) of each one of the two transistors of a single-pole-double-throw transistorized switch are independently sensed by a sensing circuit for producing a fault signal, whenever the V ce of each transistor concurrently approaches or exceeds the magnitudes of first and second DC reference voltages, respectively, by predetermined differentials. Control logic is responsive to the fault signal for removing the base drive from the conducting one of the transistors. An RC network is included in the sensing circuit, for delaying the production of the fault signal, both to avoid false triggering of the control logic, and to provide time for sequentially turning off one transistor and turning on the other transistor.

Acceleration/deceleration control circuit for a stepping motor

Abstract: An acceleration/deceleration control circuit for a stepping motor includes a plural stage up/down counter connected to a source of pulses of constant repetition rate. The up/down counter output is connected to a decoder, such as a digital/analog converter, and conventionally, the output of the decoder is coupled to a variable rate oscillator, whose frequency increases, for example, as the output voltage of the digital/analog converter increases, and vice versa. The variable rate output is provided as an input to the stepping motor. In the improved arrangement a series RC circuit is coupled to the output of the decoder and the input of the variable rate oscillator is connected across the capacitor.

Controlled activation of reserve power supplies

Abstract: A time-delay RC circuit, having a preselected time constant, is connected ross a reserve battery undergoing activation. The function of the circuit is to hold off the application of the load of a power utilization device until the battery is sufficiently activated. Since the drain rate of the time-delay circuit is very small, it does not retard activation via polarization as would be the case if the full load were draining the battery during activation. A first switching transistor is connected across the charging capacitor of the RC circuit and turns on when the time constant is reached. When the first switching transistor is turned on, it turns on a second switching transistor connected between the battery and the utilization device.

Apparatus with a single input connectable to electrical energizing sources of different character

Abstract: A portion of the apparatus, which requires low voltage DC energy for its energization, is connected in series with an SCR between a single pair of input or energizing terminals. A series RC circuit is connected across the SCR, and the junction within this series circuit is connected through a zener diode to the gate of the SCR. When low voltage DC is applied between the input terminals, it turns on the SCR continuously and effectively appears across the noted apparatus portion to properly energize the latter. When high voltage AC is applied between the same input terminals, it turns on the SCR for only a predetermined part of each cycle of the AC. This part is made to be such that the resulting voltage across the noted apparatus portion is effectively the same when the high voltage AC is applied between the input terminals as it is when the low voltage DC is applied between the same input terminals.

Detector circuit locates tripped fuse in complex supply equipment - by detecting voltage on RC circuit that shunts diode in series with fuse

Abstract: The detector circuit locates a tripped fuse in complex power supply equipment containing many fuses each of which is in series with a diode Each fuse (S2) is connected to a high input impedance detector (M) and has its series diode (D2) shunted by an RC circuit (RC2) The detector responds when the fuse trips out The fuse is coupled to a full wave rectifier bridge (G) inside the detector The bridge output is smoothed (C) and it is electrooptically coupled (OK) to a failure indicator (SM) The bridge output also lights an LED (LD) coupled after the smoothing capacitor

Some observations on single-element control sine-wave oscillators

Abstract: A new generalized approach to the study of the variable frequency sine-wave oscillators in active RC filters having a single-element control facility is presented. The constraints on the filter functions which are amenable for generation of such oscillations with feedback are derived and a number of exemplary circuits are given and also their frequency and gain limits in tables. The oscillation stability is also studied following Loeb's criterion of limit cycle stability for systems having saturation characteristics in the active parts. The circuits are also shown to yield VCO's with voltage controlled FET as the frequency controlling parameter, The possible configurations of the amplifier circuits with operational amplifiers as the building block are considered including a discussion on bandwidth limitation.

Engine ignition system with variable spark internal duration

Abstract: An RC circuit branch determines the duration of the period for which the primary circuit of a spark coil remains interrupted after the main peak of the spark discharge in the secondary circuit that includes a spark plug. Engine speed and engine temperature are used to shorten the period during which the secondary circuit is allowed to entertain a spark discharge. As engine speed increases the spark discharge period is reduced until a certain speed is reached after which the spark discharge period remains constant with further increase of engine speed. Engine temperature is also used to shorten the spark discharge period by the use of a temperature sensitive resistor. The charging and discharging of the storage capacitor of the RC circuit branch are separately controlled by the shunt circuits in which diodes are interposed and in one embodiment an additional capacitor can be switched into parallel into the RC circuit branch when the engine is starting up. The degree of intake manifold vacuum can also be used to modify the operation of the circuit.

Effects of finite gain-bandwidth product on three recently proposed quadratic networks

Abstract: The effects of finite gain-bandwidth product on the networks of Akerberg and Mossberg, Wilson et al, and Mikhael and Bhattacharyya are compared with each other and with the state variable network To facilitate the comparisons, these effects are presented in an easily interpreted graphical form

Fault current protective circuit - has summator transformer and has auxiliary windings feeding biasing generator and RC control

Abstract: A fault current protective circuit consists of a summing current transformer whose primary windings are formed by the main conductors of an AC single-phase or three-phase supply. The secondary windings of the transformer are connected to a trigger. There are auxiliary windings connected to a generator to produce an AC biasing magnetisation of the current transformer. The secondary windings are connected to a rectifier circuit. The frequency of the biasing magnetisation is large compared to the main frequency. A RC network is connected in parallel to the rectifier circuit. The time constant of the RC network is approximately equal to the period of the biasing oscillations. There is a discriminator circuit parallel to the RC network. When the voltage of the RC network drops below a limiting value it will produce a trigger pulse.

Analog-to-pulse density converter

Abstract: The analog-to-pulse density converter of U.S. Pat. No. 3,955,191 is modified to provide high stability gain with temperature compensation, auto-centering and defined d.c. offset to reduce noise at low signal levels. The modified circuit has reduced power dissipation. The modulator has a stabilized current switching circuit feeding an RC network which is terminated by two D-type flip flops clocked by a high frequency pulse train. Negative feedback from both of the flip flops causes the circuit to generate a pulse density modulated (PDM) output signal related to a given input signal.

A note on frequency and Q limitations of active filters

Abstract: The effect of finite gain bandwidth of nonideal operational amplifier on the performance of most of the second-order active filters is presented. The variation of the center frequency \omega_0 and the quality factor Q of these filters due to the finite gain bandwidth is evaluated in detail. The usefulness of these filters for specific tolerances on \omega_0 and Q are also pointed out.

Actuating circuit for D.C. motor

Abstract: A D.C. motor control circuit including a wheatstone bridge type speed regulating circuit with a transistor arranged for detection of the counter-EMF developed across the motor armature to control operation of a drive control circuit. In one embodiment of the invention, an actuating circuit comprises a constant voltage source formed from a constant current circuit connected parallel to an electrical power supply source for the motor and a variable resistor connected in series to the constant current voltage source. A diode applies the output of the variable resistor to the base of the transistor to thereby effect conduction of this transistor.

Active realization of nth-order low-pass transfer functions

Abstract: A new active RC circuit realizing the general n th-order low-pass voltage transfer functions using n Norton (current differencing) amplifiers is presented. In this realization minimum number of capacitors and n active elements are used, the element values being given in terms of the transfer function coefficients.

Counting circuit for determining the incoming frequency or received channel in a high-frequency superhet receiver

Abstract: The counting circuit is particularly useful in a high-frequency superhet receiver including IF filters, such as ceramic filters, available as completed units having definite, pre-aligned IF values, and is of the type in which the oscillations of an AM or FM local oscillator, the frequency of which differs from that of the received signal by the frequency of the IF stage of the receiver, are counted periodically by an electronic counter with each such count taking place within a predetermined gate time. In such a counting circuit, during the counting operation, a number of oscillations correspondng to a predetermined fixed number of oscillations occurring at the IF of the receiver is either subtracted from or added to the oscillations of the AM or FM oscillator so that the count of the counter indicates the incoming frequency or received channel. The gate time is determined by the pulse duration of periodically generated pulses and, in accordance with the invention, deviations of the actual IF of the IF stage relative to the predetermined fixed value of the IF taken into account during the counting operation, are compensated by shifting the leading edge, determining the beginning of the gate time, to vary the duration of the periodically generated pulses. Such shifting of the leading edge can be effected in an RC circuit including either a potentiometer, fixed value voltage dividers, or a plurality of potentiometers selected by selector switches.

Cable equalization resonant amplifier circuit

Abstract: A cable equalization resonant amplifier circuit for compensating for the signal-attenuation effects of a coaxial cable connected with the amplifier circuit and having a length of up to one-half mile. The gain of the amplifier circuit is matched with the attenuation characteristics of the coaxial cable over a wide range of frequencies by employing an LC resonant circuit with a Q of approximately 1 in the emitter circuit of an amplifying transistor. The gain for the amplifier circuit is established to match the attenuation characteristics of the coaxial cable at low frequencies by an RC circuit coupled with the amplifying transistor and the LC resonant circuit. The maximum or peak desired value of gain for the amplifier circuit at the resonant frequency of the LC resonant circuit is established by a resistor connected in series with the LC resonant circuit and a resistor in the collector circuit of the amplifying transistor.

Impact fuse with piezoelectric generator - has two parallel RC circuits and transistor ensuring fuse safety

Abstract: The impact fuse has piezoelectric generator, and is safe against inadvertent actuation. It is highly efficient and its sensitivity is independent of the type of ignition material. The output terminals of piezo generator (P) has first parallel circuit with capacitor (C1) and resistor (R1). This circuit is connected to collector electrode (K1) of a transistor (Tr1) whose emitter electrode (E1) is connected via igniter (Z) to earth potential and to first circuit. The base electrode (B1) is connected to emitter electrode (E1) via second parallel circuit (C2, R2).

Current limiting device for an a.c. motor

Abstract: A device for limiting the current in an a.c.motor having a commutator adapted to be supplied with current by a single-phase current source. The device comprising a triggerable silicon-controlled rectifier component connected in series with the motor and in parallel with an RC phase-shifting circuit furnishing the control voltage of the rectifier component. The capacitive branch of the RC circuit is connected in parallel with a shunt circuit which shunts a certain quantity of the charging current of the branch for modifying the trigger instants of the rectifier component. The shunt circuit comprises two transistors of opposed conductivity types which are connected with a common emitter configuration, the collector-emitter circuits of the transistors being connected in parallel with the capacitive branch. The limiting device further comprises a control circuit furnishing two d.c. control signals whose magnitudes are a function of the intensities of the two half-cycles of the current flowing in the rectifier component. The bases of the transistors are respectively subjected to the control signals so that the shunt circuit can shunt, beyond a predetermined current threshold of the current in the motor, a notable part of the two half-cycles of each period of the current.

A universal compensation scheme for active filters

Abstract: A finite gain-bandwidth product, of the operational amplifier restricts the use of active filters to low frequencies. Knowing the gain-bandwidth product of the operational amplifier and its variations with respect to the bias voltages and temperature, the high frequency performance of the filters can be, exactly predicted. Suitable compensation schemes can then be incorporated in these circuits to stabilize their high frequency performance against variations in the bias voltages and temperature. Variations in the performance factors due to the amplifier pole are studied for a few active RC filters. A compensation scheme is suggested which results in an extension of the useful frequency range of operation of these circuits.

Horizontal deflection circuit with high voltage selection capability

Abstract: A television receiver circuit includes a voltage regulator with a feedback circuit for providing a regulated B+ operating voltage, a horizontal deflection circuit including a resonant retrace circuit for generating a scanning current in a deflection winding for producing a raster, a high voltage circuit for providing an ultor voltage for beam current, and a high voltage protection circuit for disabling normal operation of the horizontal deflection circuit when the ultor voltage exceeds a predetermined magnitude. An impedance is included and is capable of being selectively coupled to the feedback circuit. A capacitance is also included and is capable of being selectively coupled to the resonant retrace circuit. Both means combined are selectively capable of decreasing the ultor voltage for preventing unnecessary disabling of the horizontal deflection circuit while maintaining a constant raster width.

Seizing current delay circuit for the test switching means of a telecommunication switching system

Abstract: A switching arrangement for a telecommunication switching system having test and seizing circuits is disclosed in which test switching means for bounce-free contact operation require a seizing current rise delayed by switching means in the seizing circuit. The improvement comprises a transistor for establishing the seizing current, a testing resistor disposed in series with the transistor and an RC network associated with the transistor. The potential across a control electrode of the transistor which is determined by the charging voltage of said associated RC network defines a control current. The potential renders the transistor increasingly conductive to current in accordance with a charging process setting in at the start of a test and seizing operation.

An Active RC Delay Line for Matched Filters Correlators

Abstract: For a matched filter correlator (MFC) required in a spread spectrum receiver, an active RC delay line has been developed and its performance evaluated. The building block of the delay line is a low pass type active RC filter with modifications to give desirable magnitude, phase and pulse response. An MFC processor for a bandwidth expansion of 15 in data communication application has been made using the RC delay lines and its experimental performance has been found to be close to the theoretical one.

Design of an active distributed RC lowpass network

Abstract: The letter considers the design of an active distributed RC network to approximate to the magnitude characteristic of an all-pole lowpass filter transfer function. The limitations of the dominant-pole method are examined and it is shown that this method can lead to significant errors for filters with equiripple passband characteristics. A method is described and design curves are given to improve the approximation.

Liq. level control device for pipe systems - generates signal to shut corresponding valves or pumps in case of leakage

Abstract: In the case of a fault, i.e. a contact between detector and an unwanted liquid, conductance or capacitance between two electrodes is changed, so that acoustic, electric or optical signals are generated. They are received by a respective receiver and shut or disconnect the valves or pumps through corresponding control circuits. The detector electrode lies at the input of an MOS inverter which is connected through a resistor to the supply voltage. The capacitor component of an RC circuit is dependent on the moisture content and this affects the resonance characteristics of a piezo-electric oscillator.