Showing papers on "Output impedance published in 1987"

Adjustable impedance driver network

Abstract: A variable impedance driver network comprises a plurality of transmission gates connected in parallel between a voltage source and an output Each transmission gate has a predetermined nominal impedance and by turning on selective gates the overall impedance of the network may be adjusted to match that required at the output

Tristate output circuit with selectable output impedance

Abstract: A tristate output circuit includes a pair of transistors having sources connected to a switchable current source and drains separately coupled to a voltage source through separate resistors and switching transistors. When the current source and switching transistors are on, the circuit operates in a back termination mode wherein it amplifies a differential input signal applied across the gates of the transistor pair to produce a differential output signal across their drains for transmission on a transmission line. The load resistors are sized to match the characteristic impedance of a transmission line so as to properly terminate the transmission line. In an open drain mode, the switching transistors are off, uncoupling the drains of the transistor pair from the voltage source so as to increase output impedance. In a tristate mode, the current source and switching transistors are turned off, thereby turning off the transistor pair and rendering the output impedance of the circuit substantially infinite.

Composite power amplifier with redundancy

Abstract: A power combiner includes an input power splitter driving a plurality (N) of amplifiers. The amplifier outputs have Z0 output impedance and are coupled by transmission (TX) lines of Z0 characteristic impedance to the junction point of a lossless power combiner. Short-circuiting switches located λ/4 from the junction power disconnect failed amplifiers from the combiner. According to the invention, a number M

Output impedance considerations for switching regulators with current-injected control

Abstract: The output Impedance of current-Injected controlled (CIC) buck regulators can be significantly reduced by deriving the current control signal from the output capacitor Instead of the Inductor. This technique Is shown to be mathematically equivalent to CIC with load-current feedforward. Performance comparisons with normally Implemented CIC and voltage control are given.

The NBS conical transducer: Analysis

Abstract: The NBS conical transducer is a sensitive, broadband device for the measurement of surface displacement as a function of time. Its uses include acoustic‐emission testing. Here, the operation of this transducer is subjected to a straightforward analysis. Although several approximations, some more dubious than others, are made, the model predicts the main features rather well. The important parameters are the size and shape of the active element, the source impedance (looking into the area whose deflection is being measured), and the terminating impedance (back load).

Analysis of the inductance influence on the measured electrochemical impedance

Abstract: The high-frequency region of the impedance diagram of an electrochemical cell can be deformed by the inductance of the wiring and/or by the intrinsic inductance of the measuring cell. This effect can be noticeable even in the middle frequency range in the case of low impedance systems such as electrochemical power sources. A theoretical analysis of the errors due to inductance effects is presented here, on the basis of which the admissible limiting measuring frequency can be evaluated. Topology deformations due to the effect of inductance in the case of a single-step electrochemical reaction are studied by the simulation approach. It is shown that an inductance can not only change the actual values of the parameters (electrolytic resistance, double layer capacitance, reaction resistance), but can also substantially alter the shape of the impedance diagram, this leading to erroneous structure interpretations. The effect of the size and surface area of the electrode on its intrinsic inductance is also evaluated.

Distributed power amplifier

Abstract: A distributed amplifier includes a plurality of field effect transistors, each having gate, drain, and source electrodes, successively coupled between an input terminal and an output terminal. The gate electrode of each one of successively coupled FETS is coupled to the input terminal through a corresponding one of a plurality of capacitors and selected ones of the drain electrodes of the FETS are coupled to the output terminal through one of a corresponding second plurality of capacitors, with said capacitors being coupled to an output coupling means comprising a plurality of transmission line sections. By providing the second plurality of capacitors to couple the drain electrodes to the output terminal, the output impedance of each one of the field effect transistors is concomitantly increased thereby permitting the periphery of the transistors to be correspondingly increased and thereby providing increased output power and gain from the amplifier circuit.

Small signal ac equivalent circuit modelling of the series resonant converter

Abstract: The small signal dynamics of the series resonant converter are investigated using an equivalent circuit modelling approach. The converter input and output ports behave essentially as nonideal current sources, so the most suitable form is the two-port y parameter model. Two such models are proposed: a continuous time version valid for low perturbation frequencies, aand a discrete time version which models the inherent sampling in the converter and is valid for any perturbation frequency less than the switching frequency. Experimental verification of the control to output transfer function and the output impedance is presented, and good agreement between theory and experiment is obtained.

Wideband (DC-50 GHz) MMIC FET variable matched attenuator

Abstract: A FET variable absorptive attenuator utilizes FETs as variable resistors controlled by voltages applied to their gate terminals, the FETs preferably being arranged in a T configuration with resistors connected in parallel with two series FETs, as well as a shunt FET in the form of a distributed shunt FET. One control voltage adjusts the resistances of the series FETs, and another controls the resistance of the distributed shunt FET. A proper combination of the two control voltages yields a desired level of attenuation with optimum input/output impedance matching. The resistors allow the series FETs to be biased well below their pinch-off voltages to minimize the parasitic capacitances of the series FETs at relatively high attenuation settings, improving the isolation for high attenuation settings at relatively high frequencies and also enabling the attenuator to function as a switch. They also improve the power-handling capability at high attenuation settings. The distributed shunt FET is split into several cells interconnected by inductive elements, providing a low insertion loss at maximum attenuation, as well as decreasing the parasitic capacitance of the shunt FET. The effects of this lower capacitance at relatively low attenuation settings can be more effectively counteracted by the inductive elements, extending the dynamic range of attenuation at relatively high frequencies. Also, the distributed shunt FET interconnected by the inductive elements compensates for the parasitic capacitances of the series FETs at relatively high attenuation settings, which yields increased attenuation with increasing frequency. Finally, the cutoff frequency of the attenuator at relatively low attenuation settings is increased.

Ocean wave energy conversion using piezoelectric material members.

Abstract: A float (10) on a body of water is mechanically coupled to a piezoelectric material member (18) for causing alternate straining and destraining of the member in response to the up and down movement of the float in response to passing waves, thereby causing the member to generate electricity. The output impedance of the float is matched to the input impedance of the member for increasing the energy transfer from the float to the member.

Impedance measuring methods based on multiple digital generators

Abstract: The paper describes automatic impedance measuring methods using several digital signal generators and one or two digital null detectors. The measuring arrangements are suitable for precise determination of impedances, for four-terminal measurements as well as for comparison of voltage dividers or impedance ratios.

The Effect of Distribution Transformers on Distribution Line Carrier Signals

Abstract: A study is made of the primary impedance of single phase power distribution transformers at frequencies of 2-50 kHz. This band includes the frequencies used for distribution line communications. A range of primary impedance values is found as the secondary impedance varies between 1 and 100% of full load. Then the effect of these transformers on the attenuation, phase constant and characteristic impedance of a power distribution line is computed. Calculations are compared with measurements reported elsewhere.

FET voltage reference circuit with threshold voltage compensation

Abstract: A voltage converting circuit has an output MIS transistor which gives a low output impedance and outputs an intermediate level of power source voltage. The output level is set with a high accuracy through a voltage dividing ratio determined by an impedance element. This impedance element is connected with a compensating MIS transistor to compensate for variations of the gate threshold voltage caused by the manufacturing process.

Digital to analog converter with switch function compensation

Abstract: A digital to analog converter including an R-2R ladder network receives digitally encoded sample signals in parallel through a set of chains of transistor switches, each chain having equal delay. The ladder network output impedance matches the characteristic impedance of a coaxial cable transmission line that couples the converter output to a utilization circuit. Output resistances of the switches which are connected to ladder network rung circuits are scaled in accordance with a predetermined algorithm to maintain symmetry of parallel connected resistive branches of the latter network seen at each rail terminal of the ladder. Three of the most significant bits of each input binary coded work are decoded to a bar code format before being coupled through the set of switch chains. Switch output conductances in the switch chains are scaled in accordance with a stage-to-stage conductance ratio F, and at selected stages of selected ones of the chains dummy-load switches are added to enable both conformance to that ratio and substantial equality of delay among all of the chains.

Differential impedance neutralization circuit

Abstract: An impedance neutralization circuit produces correction currents to compensate for the effects of parasitic impedance on the output voltage of an amplifier. In the described embodiment, the neutralization circuit includes a pair of emitter followers, one coupled to the collector of each transistor of a common base amplifier for sensing the output voltage at each collector. A pair of transistors are coupled one to each emitter follower for applying the sensed voltage across a neutralizing impedance proportional to the parasitic impedance seen at the collector of the opposite transistor of the common base amplifier. The voltage applied across the neutralizing impedances produces a correction current. The correction current is summed with a distortion current of proportional amount but opposite sign produced by the output voltage applied across the parasitic impedance to produce a substantially error-free output voltage.

Circuit Models and Simulation Analysis of Electromyographic Signal Sources-I: The Impedance of EMG Electrodes

Abstract: The impedance of surface and intramuscular biopotential electrodes was measured during rest and muscle contraction in humans. A frequency-dependent parallel RC circuit model of the skin-electrode interface that captures the dependence of this impedance on the size and geometry of electrode placement was developed and its components were estimated. The model could explain between 86-97 percent of the variations in impedance (Z), 72-92 percent of the variations in resistance (R), and 34-93 percent of the variations in capacitance (C). The impedance and resistance of these electrodes decrease by about tenfold for a 20-fold increase in frequency, while the capacitance decreases by about twofold for the same change in frequency (f). Thus, the overall FRC factor of this parallel RC circuit model remains nearly unchanged over the range of frequencies studied (50-2000 Hz). A significant difference was found between the impedances of the electrodes comprising the differential electrode pair. This imbalance in impedance was between 8-14 percent for surface electrodes and 6-19 percent for wire electrodes. These data provide essential design criteria for the development and simulation of a system for the measurement of electromyographic activity.

ECL high speed semiconductor memory and method of accessing stored information therein

Abstract: A hybrid ECL memory includes a hybrid memory array 36 which utilizes cross coupled CMOS latches (70). Each CMOS latch (70) is accessed by an ECL decoder (40) and an ECL Word Line driver (42) to read data therefrom. Data is accessed through a bipolar transistor (120) for output to an ECL sense amp. The column select operation is provided by an ECL decoder (50) to select both the Read and the Write operation. The Write operation is provided with emitter coupled logic by pulling up one of the storage nodes in the CMOS latch (70) with a low source impedance PNP transistor (122). Selection is provided by varying the Word Line between two voltages through a low source impedance transistor (78) with the voltages being ECL compatible.

Impedance measuring apparatus for R.F. baseband signals over two wire telephone lines

Abstract: A simple impedance measuring tool is provided for performing an accurate but inexpensive determination of impedance and assurance of an impedance match in an installation environment. The apparatus operates according to a method wherein the average instantaneous voltage on a transmission line is sensed based on the integration of a series of reflections stimulated by a pulse generator. The apparatus comprises a fast repetitive pulse generator, a fast comparator, a flip-flop and a means for integrating the output of the flip-flop to produce an output voltage which can be read by a simple low-cost meter such as a d.c. voltmeter. The output of the comparator is coupled to the data input of the flip-flop, which is driven at its clock input by a variable phase clock output of the pulse generator. The absolute time delay or phase determines the distance at which the measurement is to be taken.

Modelling a current-programmed buck regulator

Abstract: A general small-signal model for current-programmed switching power stages is used for design-oriented analysis of a 150W buck regulator. The model, into which the current-programming minor feedback loop is absorbed, exposes the desired tendency towards "constant" output current. The regulator voltage loop remains the only explicit feedback loop, allowing the regulator closed-loop properties to be easily obtained from those of the open-loop current-programmed power stage. The design-oriented analytic results allow easy inference of the effects of element changes on the regulator performance functions. Results are obtained for the regulator line-to-output transfer function (audio susceptibility) and output impedance.

Electric discharge machining method and device

Abstract: An electric discharge machining device, in which a pulse voltage is repeatedly applied between electrodes, which are an electrode and a workpiece to be machined, to cause electric discharge between the electrodes and thereby machine the workpiece. The electric discharge machining device includes a switching device (4) connected between a power source and the machining section, for controlling energy supplied by the power source; interelectrode impedance detecting apparatus (10) for detecting an interelectrode impedance affected by the variation in place of electric discharge which takes place between the electrodes; discharge detecting apparatus for detecting when electric discharge takes place between the electrodes; and a control device (18). The control device utilizes the output of the interelectrode impedance detecting apparatus to calculate a power source internal impedance to obtain a desired no-load voltage, and a power source internal impedance to obtain a desired current at the detection of electric discharge to thereby control the switching device. As a result, the discharge machining operation is stably carried out, the machined surface is uniform in surface roughness, and for a desired surface roughness the highest machining speed can be employed.

Latch cell family in CMOS technology gate array

Abstract: The invention provides novel implementations of a latch cell in CMOS gate array technology to produce latch dissymmetry and permit a single ended data input. The dissymmetry is produced by increasing the output impedance of the second stage of the latch cell, which can be done, either in a DC or in an AC mode, or even in a mixed version of both modes.

Electronic switching apparatus having impedance matching circuitry for ultra-high frequency signals

Abstract: A switching device is realized by means of two amplifier paths which are controllable by means of transistors. The collectors of output transistors (T1, T1B) are connected together, without an impedance matching circuit for each path, to a common point (10) being connected to an impedance matching circuit (L5, R7) which is common for the two paths. This switching device is particularly used for selecting signal paths between 1 and 2 GHz in systems for receiving television signals by satellite.

Drive and control circuit for laser diode

Abstract: A drive and control circuit for laser diodes includes: a first switching element connected in series to a laser diode connected to a constant-current source for actuating the laser diode when a binary drive signal is at one level thereof; an impedance element connected in parallel to the series circuit of the laser diode and the first switching element, the impedance element being connected to receive the constant-current source together with the laser diode and having impedance characteristics substantially equal to those of the laser diode and the constant-current source; an integrator circuit for integrating the data at the one level; an impedance control circuit for variably controlling the impedance of the impedance element in response to the integrator circuit; and a second switching element connected in series to the impedance element for actuating the impedance element when the drive signal is at the other level. Furthermore, an alternative embodiment of the drive and control circuit includes the combination of a comparator, an integrator circuit, a constant-current circuit, a counter and a timer.

Microwave line converter

Abstract: PURPOSE: To improve the electric separation between input/output lines by providing a transistor (TR) having prescribed input/output impedance between 1st and 3rd terminals and between 2nd and 3rd terminals, providing a microstrip line between the 1st and 3rd terminals and providing a coplaner line between the 2nd and 3rd terminals. CONSTITUTION: In giving a microwave signal to a coplaner line 12 comprising a center conductor 9 and ground conductors 10, 11 via a connection terminal or the like, the said microwave signal is inputted to a grounded-gate MESFET 20, where processings such as impedance conversion from the said input impedance into the said output impedance and amplification are executed and the result is outputted to a microstrip line 4. Since electric isolation action exists between a source electrode 22 and drain electrodes 23a, 23b of the MESFET 20 as well known, the input/output lines 4, 12 are isolated electrically, and even when reflection exists in a circuit connected to the microstrip line 4, its reflected wave does not appear on the coplaner line 12 without being modified. Thus, the countermeasures as above such as an isolator against the reflected wave are not required. COPYRIGHT: (C)1988,JPO&Japio

Analysis and Performance of a Fixed Filter-Thyristor Controlled Reactor (FF-TCR) Compensator

Abstract: A fixed Filter-Thyristor Controlled Reactor (FF-TCR) type of compensator is proposed to improve the power factor of a single phase thyristor-controlled inductive load and it is shown that this compensator gives better power factor improvement than the more generally used FC-TCR type of compensator. Analysis is carried out for the exact equivalent circuit of an FF-TCR compensator containing two filter branches tuned to the third and the fifth harmonics respectively. It is shown that with an FF-TCR compensator the power factor improvement is much better when the source impedance is large. However, even with a small source impedance, a reasonable improvement in power factor is realised. It is further shown that even when the source impedance is large the distortion in the terminal voltage waveform is kept within reasonable limits. The analytical results are verified experimentally.

The Dynamic Impedance of Radio Frequency Heating Generators

Abstract: The importance of the dynamic impedance in the design of radio frequency heating generators is highlighted. Established procedures are used to obtain graphically the working parameters of a number of triodes used in industrial processing operating under Class C Conditions. It is shown that the dynamic impedance reduces from the range 24–9 KΩ at no load condition to about 1–2 kΩ at near full load conditions. The effect of the material loss factor on the dynamic impedance and hence on matching in the case of inductively coupled applicatiors is quatitatively described using a simple model.

Ultra-broadband impedance matched electrically small self-complementary signal radiating structures with impedance-inverting feed for complementary pairs using thin wire elements

Abstract: Ultra-broadband impedance matched electrically small self-complementary pair antennas using thin wire elements with impedance inverting feed are presented. Efficiencies are determined by achieveable loss resistances in the radiating structure itself, rather than the (limited) quality of an external loading coil, and by energy channeled into the difference port of the feed hybrid, that is used to match two complementary impedances. Broadband impedance loci are achieved for thin radiators by impedance inverters placed prior to the complementarizing circuit. Impedance matching is then accomplished in a standard broadband hybrid or "Magic Tee" feed circuit.

Apparatus for measuring noise characteristics

Abstract: A device for measuring characteristics of a semiconductor device using a noise measurement system and an impedance measuring system includes an input probe and an output probe for providing connection to the semiconductor device. The device also includes first and second variable impedance devices for respectively varying a source and a load impedance, and respectively connected to the input and output probing devices. First and second switching devices are respectively connected to the first and second variable impedance devices. The switching devices selectively connect the first and second variable impedance devices to the noise measurement system, and selectively connect the first and second variable impedance devices to the impedance measuring system.

Gain enhancement technique for differential pairs

Abstract: A gain enhancement technique is presented for increasing the output impedance of a differential pair. It is useful when trying to realise fast single-stage amplifiers, without having to accept the compromise of very low gain. The only major disadvantage is that either a larger power supply voltage or a smaller maximum signal swing must be tolerated.