Showing papers on "Negative impedance converter published in 1976"

Monitoring system for voltage tunable receivers and converters utilizing an analog function generator

Abstract: A system for monitoring the channel to which a remotely located voltage tunable receiver or converter is tuned includes a comparator for comparing the magnitude of the tuning voltage with an internally generated reference voltage to determine the channel number. The reference voltage is generated by a counter driving a linear digital-to-analog converter. The output of the digital-to-analog converter is modified with an analog function generator to provide a piecewise linear approximation of the receiver tuning voltage versus channel number characteristic. A window comparator is utilized to compare the output of the function generator with the tuning voltage and to stop the counter and transfer the contents of the counter to an output circuit when the magnitude of the reference voltage approaches that of the tuning voltage. The contents of the counter at the time the counter is interrupted is indicative of the channel number of the station being received.

Compression and expansion system with enlarged dynamic range

Abstract: A compression and expansion system comprises a control circuit including a variable impedance element, whose impedance is varied in accordance with a control signal applied thereto. The system has a frequency-response characteristic which varies in accordance with variation of the impedance of the variable impedance element. A control signal is formed in accordance with the level of an input signal and is applied to the variable impedance element of the control circuit thereby to vary the impedance thereof. A switching means forms passing paths in a manner such that, at the time of compressing, the input signal is supplied by way of the control circuit to a negative feedback amplifier. At the time of expanding, the input signal is supplied to the negative feedback amplifier, and, at the same time, the output of the negative feedback amplifier is fed back by way of the control circuit to the input of said negative feedback amplifier. The control circuit comprises a variable high-frequency range increasing circuit which operates when the input signal level is relatively low. The control circuit increases the high-frequency component in accordance with the variation of the impedance of the variable impedance element. A variable high-frequency range decreasing circuit operates, when the input signal level is relatively high, to decrease the high-frequency component in accordance with the variation of the impedance of the variable impedance element.

Low-power monolithic COS/MOS dual-slope 11-bit A/D converter

Abstract: A single-chip, auto-zeroing, dual-polarity, single power supply A/D converter will be discussed, citing CMOS amplifier techniques used and performance results.

Temperature compensated constant voltage apparatus

Abstract: A temperature compensated constant voltage circuit utilizing a constant current supply circuit having a positive temperature coefficient of current for supplying current to a nearly constant voltage dropping circuit. The voltage dropping circuit includes a zener diode which has a negative temperature coefficient. The combination of the positive and negative coefficients cooperate to produce a temperature stable constant voltage circuit.

Methods and means for identifying and testing circuit connections

Abstract: The task of identifying the terminals to be interconnected and not interconnected, and whether connection is proper in a complex electrical system, such as at the main distribution frame of a telephone central office, is made possible while the system is in operation under power without adversely affecting its operation of being adversely effected. This is done by connecting the combination of a load impedance and a test voltage source across the test points and measuring the voltage across the load. If the measured voltage exceeds the test voltage, the load impedance is maintained at a high value. If it does not exceed the test voltage, the value of the impedance is reduced for the test. Thus, the test impedance is either greater or lesser than the impedance presented by the telephone system at the test terminals. The test results are interpreted in the view of whether the test terminals should or should not be connected when properly wired.

Automatic impedance matching using resistive and reactive diodes

Abstract: An impedance matching device is disclosed which automatically maintains h isolation between two opposite ports of a four port hybrid while the impedance of one of the other ports varies randomly. The device operates by sampling the signal at the output of the port it is desired to isolate and adjusting the impedance of the port opposite the port of randomly varying impedance in such a way as to minimize the sampled signal and thereby maintain isolation.

Voltage indication means of an electronic flashing device

Abstract: Voltage indication means for an electronic flashing device in which a low D.C. voltage is converted to a high D.C. voltage by a DC-DC converter circuit and energy stored in a main discharging capacitor is supplied to a flashing discharge tube to fire it, wherein the charged voltage of the main discharge capacitor is indicated by utilizing the fact that the charged voltage of the main capacitor is in equivalent relation with a voltage generated in the DC-DC converter.

Delay circuits using negative resistance CMOS circuits

Abstract: A negative resistance circuit constructed of complementary field effect transistors has several applications. A voltage change at an input to the negative resistance circuit alters the current at the input node in a direction inverse to that normally caused by such a voltage change. The circuit can be used to speed up the charging or the discharging of a circuit node capacitance.

Three-phase, quasi-square wave VSCF induction generator system

Abstract: A plural switch matrix is connected as a direct ac-to-dc converter between an induction generator and an a-c load. The generator provides three-phase output energy which is switched and controlled by the converter, to supply a controlled three-phase quasi-square wave (QSW) voltage to a load. The converter switching provides periodic shorts across the generator terminals, translating some of the mechanical input energy into electrical energy to sustain the generator field. The converter is regulated by gating signals from a combinational logic circuit.

Theory of negative resistance of junction field-effect transistors

Abstract: A general theory of the voltage-controlled negative resistance in a field-effect transistor is presented. The prerequisite to the negative resistance is mathematically determined as a relation among the source-gate voltage, the source-drain voltage, and the pinchoff voltage. It is suggested that there will be a variety of circuit configurations with the positive feedback function applied to the gate of the field-effect transistor. Three basic examples of the practical application of the theory are also given.

Guard circuit for high impedance signal circuits

Abstract: Current leakage from high impedance signal circuits or networks of the type useful in the feedback paths of operational amplifiers is inhibited or prevented by circuit guarding. A lower impedance, parallel path provides a guard circuit that protects the signal circuit elements from excessive self-generated current leaks during closed loop use of operational amplifiers. The guard circuit includes equal potential nodes in the lower impedance path that are juxtaposed to corresponding nodes of the signal circuit elements. Current leakages, that may occur in the signal path, are mostly intercepted by the lower impedance guard circuit preventing the formation of electric fields or current leakage paths that would affect normal signal circuit performance.

Unipolar wide-range current-to-frequency converter

Abstract: In a unipolar version of an analog-to-digital converter of low-level signals involving a self-zeroing current-to-frequency converter, which virtually eliminates the effects of voltage offsets at the input to the converter while avoiding large leakage currents, improved circuitry is provided in order to avoid paralysis of the converter which could be caused by small input currents or charges of polarity opposite to that of the normal signal current or by drifts in the converter input voltage which produce a negative-charge offset. The circuitry includes provision for the automatic introduction at the converter input of a relatively-large restoration current with the same polarity as the signal current, and this current can also be used for converter checking and calibration. One version of this circuitry involves exposing a junction diode at the converter input to light, causing it to act as a photodiode. One easily controlled source of such light may be a light-emitting diode conducting a suitable current placed in close proximity to the junction diode within the same enclosure. When the junction diode forms a part of a secondary feedback loop used during the discharge period of a primary capacitive feedback, then exposing it to light speeds up the secondary feedback, thereby reducing converter dead time. Other devices may be used for current introduction at the converter input, including a mechanical switch, but they are less preferable from the standpoint of leakage current, size and speed of response.

Efficient AC energy converter - has internal resistance of DC energy converter connected into AC circuit

Abstract: The ac energy converter has improved energy conversion efficiency compared with direct conversion systems such as thermocouples, thermionic valve diodes, photovoltaic cells, fuel cells, magnetohydrodynamic converters etc. To this end, the electrical internal resistance of a direct energy converter is connected into an a.c. circuit, and means are provided to ensure that the current flows through the internal resistance of the direct energy converter as rectified current, and that an impedance is provided in the a.c. circuit so as to limit the current. The impedance value is greater than the value or magnitude of the internal resistance of the direct energy converter, which is a laser diode.

Apparatus for converting a potential signal developed between two high impedance electrodes to a current signal and for transmitting this current signal to a remote location over a two wire transmission

Abstract: A two-wire voltage to current converter and transmitter for extremely high output impedance transducers has an input which floats with respect to the power supply ground potential and is referenced to the power supply ground potential by means of a level shifting comparator.

A novel detection circuit for Auger spectroscopy

Abstract: An inexpensive detection system involving an active negative capacitance amplifier is described which is suitable for use with two-grid retarding field electron spectrometers. An inexpensive phase locked loop integrated circuit may be substituted for the normal lock-in amplifier for all but the most critical applications leading to an unambiguous location in energy of a particular Auger line.

Current inversion impedance converter using operational amplifiers

Abstract: A current inversion impedance converter that requires three amplifiers is presented. The residual error in the g parameters is negligible for practical applications. The network is short circuit stable at one port and open circuit stable at the other. A novel application of the circuit is also briefly described.

Negative conductance network

Abstract: Signal transmission circuit characteristics are supplemented by a negative conductance circuit in which current sources of complementary polarity are connected in shunt between the conductors of the signal circuit. Changes in the voltage level of one side of the signal circuit are sensed at a point common to the two sources and applied through a positive impedance to control the current output magnitude of one of the sources for effecting a supplementing of the signal circuit current as though the changed voltage level had been applied in the presence of a negative form of that impedance connected at that common point. In additional embodiments, different, or variable, positive impedance are connected in the sensing circuit output coupling to cause the negative of such impedance to appear at such signal circuit terminal.

Apparatus for storing a voltage analogous to an exposure parameter in photographic cameras

Abstract: Apparatus for storing a voltage analogous to an exposure parameter in photographic cameras with an electronic timer and with electric exposure measurement, having the characteristics that an analog-to-digital converter is provided as the storage unit, containing a digital-to-analog converter, the output voltage of which is fed to a comparator wherein this output voltage is compared with the voltage delivered by the exposure meter part. The signal obtained at the comparator output in the case of voltage identity stops the analog-to-digital converter and the voltage remaining at the output of the digital-to-analog converter controls the respective exposure parameter in the camera.