Showing papers on "Output impedance published in 1990"

Realization of current mode all-pass networks using a current conveyor

Abstract: Two novel networks are proposed for realizing a current-mode all-pass filter with high output impedance, using a single current conveyor (CC II) and four passive elements. The networks can be used in cascade without requiring an impedance-matching device. Even with a nonideal CC II, the networks can realize all-pass networks with slightly altered values of the gain and the center frequency. >

Battery impedance measurement apparatus

Abstract: A battery impedance measurement apparatus for battery powered implantable medical apparatus in which current source means and reference impedance means are selectively connected across the battery after it has been isolated from the medical apparatus, and the resulting currents of interest are digitized to provide a factor directly related to the value of the internal impedance of the battery. The digitized value may be telemetered out of the implanted medical apparatus to enable critical decisions to be made based on the remaining life of the implanted battery. The same measurement apparatus can be used to form an accurate end-of-life signal.

Data processor having an output terminal with selectable output impedances

Abstract: A data processor has at least one output terminal which a user of the data processor can vary the output impedance thereof depending upon the application environment of the data processor. A first output buffer of an output buffer stage has a predetermined output impedance and is coupled between an input of the stage and the output terminal. The first output buffer provides a first output terminal impedance. A second output buffer having a lower output impedance than the first output buffer may be selectively coupled in parallel to the first output buffer to reduce the output impedance of the output terminal. The coupling of the output buffers is controlled by a user of the data processor who provides a control input for selecting one of a plurality of predetermined output terminal impedance values.

Measurement and analysis of radio frequency glow discharge electrical impedance and network power loss

Abstract: Impedance measurement of rf glow discharges is a convenient diagnostic tool that can be used to estimate specific discharge properties based on a simple electrical analog model. Accurate measurements require minimization and characterization of stray impedance. In this study, the stray impedance is minimized by using a triaxial power feedthrough and electrode shield configuration. The remaining stray impedance is characterized using a two‐port circuit model to represent the impedance between the voltage and current probes and the electrode. The two‐port parameters are determined by unterminating [R. F. Bauer and P. Penfield, Jr., IEEE Transactions on Microwave Theory and Techniques MTT‐22, 282 (1974)] the network, which involves measuring the impedance of the reactor system with three or more known impedances inserted between the electrodes. Based on voltage and current measurement, the discharge impedance can then be determined during discharge operation. Impedance measurements and property estimations a...

The ‘Secondary Source’ Method for the Measurement of Pump Pressure Ripple Characteristics Part 1: Description of Method:

Abstract: The difficulties involved in measuring a pump fluid-borne noise rating are discussed A new test method is described for measuring the source flow ripple and source impedance of positive displacement hydraulic pumps This is called the ‘secondary source’ method, and is based on the analysis of the wave propagation characteristics in a circuit which includes the pump under test and an additional source of fluid-borne noise

Cascadable current-mode single CCII biquads

Abstract: A new configuration for the realisation of current-mode single-CCII-biquad (SCB) filters with high output impedance is presented. It can synthesise lowpass, bandpas, highpass, notch, and allpass filtering functions woth a single CCII connected to five passive RC one-port elements. The quality factor, Q, and the central frequency, ω 0 , of the proposed SCBs are insensitive to the current tracking error of the CCII. These SCBs have the advantages of low passive sensitivities and independently adjustable ω 0 or Q

Elimination of the positive zero in fixed frequency boost and flyback converters

Abstract: It is shown how a fixed-frequency, leading-edge modulated pulse width modulation can eliminate the undesirable positive zero in practical boost and flyback converters. This allows a substantial improvement in the closed-loop characteristics. Several techniques are employed to predict this result. The design procedure for elimination of the positive zero is presented. Experimental verification is provided. By providing an effective feedforward of the load current, this technique ensures excellent load transient response and low output impedance. There are several advantages to this technique. Measurement of the control-to-output transfer function cannot be easily performed. Also, the positive zero elimination is dependent on the capacitor ESR value. This technique can be susceptible to noise since the output voltage switching ripple is not filtered in the compensation network. >

An automatic system for adjusting the output impedance of fast cmos drivers

Abstract: An automatic system for adjusting the output impedance of fast CMOS drivers, wherein the output impedance of a plurality of slaved drives is adjusted by a circuit for measuring and correcting mismatch between the output impedance of one of the drivers, taken as reference and dedicated for this purpose, and the impedance at the input of a reference transmission line, equal to the lines connected to the other drivers. The measuring of the output impedance of the reference drive is indirectly effected by inserting at the reference drive input a clock signal and by periodically measuring the output on the reference transmission line in correspondence with the positive half-period center. The measured voltage is sent to a comparator whereby it is compared with a reference level equal to half the maximum level present in the line under matching conditions and, according to the comparison result, a signal is supplied capable of charging or discharging a capacitor, across whose terminals a voltage controlling the driver output impedance is available.

The ‘Secondary Source’ Method for the Measurement of Pump Pressure Ripple Characteristics Part 2: Experimental Results

Abstract: Tests, using the ‘secondary source’ method, have been performed to measure the fluid-borne noise characteristics of several hydraulic pumps. This method has proved to give very repeatable measurements of source flow ripple and source impedance, and the results show good qualitative agreement with theoretical models. Results are verified by using them to predict the pressure ripple in a typical hydraulic circuit and comparing this with measured pressure ripple. Correlation is shown to be good.

A new efficient NanoTip lead.

Abstract: The ideal lead has low, stable acute and chronic thresholds, high pacing impedance, and good sensing. Leads with low, stable thresholds have been developed, but pacing impedance has been in the 600 omega region. One way to increase pacing impedance is to decrease the electrode's surface area. The threshold performance and sensing ability of less than 5 mm2 electrodes have been considered questionable, up to now. We have developed a 1.5 mm2 porous, platinized, steroid-eluting electrode and have demonstrated in canine studies that it has excellent performance. Chronic thresholds are low at about 0.65 +/- 0.28 V (ventricular) and 0.42 +/- 0.12 V (atrial) at 0.5 msec. Chronic pacing impedance is in the 1200-1300 omega region, but mean chronic R and P wave source impedance is less than or equal to 1500 omega. Sensing is excellent, with almost double the P wave amplitudes usually measured in the canine.

Applications of a first-generation current conveyor in current-mode circuits

Abstract: In current-mode filter circuits which utilise a single current conveyor as the only active device, the first-generation current conveyor permits feedback of the response without connecting filter elements to the output port. Complex poles can be realised in such circuits while maintaining high output impedance. The utility of this observation is illustrated by the derivation of new second-order, complex-pole, current-mode, all-pass networks that employ a single current conveyor. Laboratory and simulation results are compared

Output impedance of PWM UPS inverter-feedback vs. filters

Abstract: The output impedance of an uninterruptible power supply (UPS), which determines the voltage distortion caused by switchmode power supplies, rectifiers, and other nonlinear loads, is reviewed. Step-wave inverters that use shunt filter traps to attenuate the voltage harmonics and thereby present a low impedance to the harmonic load currents of the same order are discussed. Another approach to reducing the output impedance of pulse-width modulation (PWM) inverters, using the negative-feedback technique of the amplifier, is also discussed. Conclusions concerning the use of filters and feedback in the design of PWMs for UPSs are summarized. >

Measurement of pH and specific ion concentration

Abstract: MEASUREMENT OF pH AND SPECIFIC ION CONCENTRATION A microprocessor-controlled pH and ion concentration meter is disclosed with improved calibration and testing procedures For calibration (standardization), the meter stores number pairs (pXa, Ea) , (pXb, Eb) where the pX values may be pH values (eg, 400 and 700) and the E values are expressed in mV/deg K When multiple standard values are stored, remeasuring one (eg, replacing Ea1 by Ea2) can be used to update the others (eg, Eb2 to Eb2) without remeasurement by applying the formula: Eb2 = Eb1 + (Ea2 - Ea1) The meter can be tested for excessive internal bias current by measuring the potential (V1) when the meter is connected to a circuit a known voltage (E1) of low impedance and the potential (V2) when the meter is connected to a circuit of the same voltage source (E1) but of known high impedance and having the meter compare (V2 - V1) to a preset limit value The meter can be tested for low internal impedance by further measuring the potential (V4) when the meter is connected to a circuit of a second external voltage (E2) and the known high impedance (R1) The meter then calculates: (V4 - V2) and compares that value to preset limits based upon E1, E2 and R1 Such limits can be derived as (Zo) (E2-El) / (R1 + Zo) wherein Zo is the minimum acceptable internal impedance

Integrated circuit fuse-link tester and test method

Abstract: A test circuit for determining whether or not fuse-links of an integrated circuit have been opened or closed properly by, for example, a laser device. The test circuit of this invention, in one embodiment, includes a variable impedance, such as a P-channel transistor, connected between a voltage source and an output terminal, the impedance having one value with a first input applied to the variable impedance control terminal and having a second, larger value in response to a second input applied to the variable impedance control terminal. At least one programmable fuse-link and a gate are connected in series between the output terminal and a source of reference potential. A means for providing control inputs to the variable impedance is connected between a test mode input signal and the control terminal of the variable impedance. The means for providing control inputs to the P-channel transistor may include a second, current-mirror-connected P-channel transistor.

Resistor-string digital to analog converters with auxiliary coarse ladders

Abstract: A digital to analog converter for the conversion of a digital signal into a corresponding analog signal. The converter has a resistive string comprising a string of first resistive segments having between segments selectable nodes including intermediate nodes wherein consecutive intermediate nodes are separated by a respective plurality of said segments. Switches provide selective coupling of at least one of the selectable nodes to an output. A decoder is responsive to the digital signal for controlling the switches. In order to reduce the output impedance of the converter and to reduce variation in the output impedance with the position of the selected node at least one auxiliary string of second resistive segments is coupled in parallel with the resistive string, providing between intermediate nodes substantially lower impedance than the respective first segments.

The small signal a.c. impedance of gallium arsenide and silicon p-i-n diodes

Abstract: The purpose of this paper is to demonstrate that the impedance of the p - i - n diode is definable as a function of frequency and depends on the diode's geometry and electronic properties. The impedance analysis includes the effects of different electron and hole mobilities, making the model suitable for modeling the a.c. impedance of both silicon and gallium arsenide - i - n diodes. The small signal model shows that for frequencies near the inverse of the intrinsic region carrier lifetime, the diode shows either capacitive or inductive reactance, depending on its geometry. The analysis also indicates that p - i - n diodes with certain combinations of geometry and carrier lifetime show a nearly constant resistance and negligible reactance at all frequencies. At high frequencies for p - i - n diodes of any geometry, the reactive component essentially disappears and the impedance is purely resistive. The series equivalent p - i - n diode impedance model is compared with measured impedance vs frequency data for both silicon and gallium arsenide - i - n diodes.

Microwave frequency range electro-optic modulator with efficient input coupling and smooth wideband frequency response

Abstract: A travelling-wave Mach-Zehnder electro-optic modulator (10) for operation at microwave electrical input signal frequencies has an electrical modulation electrode structure (26,34) which constitutes a coplanar waveguide (24). An electrical input signal connector (80) is coupled to a microstrip line (38) having an output impedance which is significantly different from the input impedance of the waveguide (24). A Chebyshev impedance matching transformer (50) couples the input signal from the input connector (80) to the modulation electrode structure (26,34), while matching the output impedance of the microstrip line (38) to the input impedance of the waveguide (24) to maximize the coupling efficiency and minimize return loss. The modulato GOVERNMENT RIGHTS This invention was made with Government support under Contract No. N66604-87-C-1126 awarded by the Department of the Navy. The Government has certain rights in this invention.

A fast-settling CMOS op amp with 90 dB DC-gain and 116 MHz unity-gain frequency

Abstract: An op amp that exhibits single-pole settling behavior using an auxiliary amplifier that boosts gain without degrading settling time is described. The technique for increasing the DC gain is based on increasing cascoding by adding an additional gain stage. In this way the output impedance present at a node is increased by the gain of the additional gain stage. >

Narrow-band, bandstop filter

Abstract: A multi-resonant notch filter incorporates a stepped impedance transmission line with impedance values going from a relatively low value and increasing upward to a relatively high value then back down to a relatively low value again A plurality of resonant cavitites is coupled to the relatively high central impedance line section of the filter Other resonators can be coupled to lower impedance sections of the transmission line

Accurate current conveyor topology and monolithic implementation

Abstract: A new current conveyor topology based on an innovative connection of Wilson current mirrors is presented. It offers significant enhancements in the areas of accuracy, frequency bandwidth, transient response, output impedance and distortion. The performance of an integrated circuit implementation of this configuration, fabricated on a complementary npn-pnp bipolar process is also described.

High frequency BiMOS linear V-I converter, voltage multiplier, mixer

Abstract: A voltage to current converter, voltage multiplier and mixer circuit. At least two differential output, common source, pairs of matched field effect transistors have cross connected drains. Those transistors which do not have their drains connected together have their gates connected together to form a first pair of voltage input nodes. The two cross connections form output nodes providing differential output currents. A pair of impedance transformation, low output impedance, buffer amplifiers have bipolar transistor output stages and a high input field effect transistor input stage. The outputs of the output stages are each respectively connected to a different one of the common sources of the differential connected pairs. The input nodes of the input stages form a second pair of voltage input nodes. A low impedance, bipolar transistor, constant dc current, biasing circuit is connected to the common sources for biasing the field effect transistors of the differential pairs in their saturation region and for biasing the bipolar transistors in their active region.

Split-drain MOSFET magnetic sensor arrays

Abstract: The design of a monolithic split-drain MAGFET magnetic sensor array, implemented in a standard 3 μm CMOS process, is detailed. The MAGFETs in the array are scanned in a raster scan fashion. The rows are scanned by allowing current to flow through all elements in a given row, while all other rows are turned off. We present two different methods for performing the column scanning. In the first method, while a row is selected, the differential current output of the sensing elements in the row is amplified by a current mirror transresistance ampfifier which provides conversion of the current differential to a single ended voltage. The outputs of the current mirrors are then multiplexed to provide the column scan. The multiplexed signal then goes into a buffer stage which provides additional amplification and lowers the output impedance for driving external loads. The second scanning method is similar, but does the column multiplexing before the current mirror amplification stage. 32 × 32 and 64 × 64 element arrays have been implemented in 3 μm CMOS, through the MOSIS facility. Experimental results on the sensitivity of individual sensing elements as well as magnetic field images produced by these arrays are presented. The problems of sensor-to-sensor non-uniformity and the sensitivity of the arrays to interference from non-magnetic influences, especially the effect of stresses in the silicon substrate of the sensor chip, are discussed.

A CMOS OTA with improved linearity based on current addition

Abstract: Current addition, an approach to the design of linear transconductance elements with a very large linear input range, is explored. Design tradeoffs are discussed and a specific circuit is simulated by SPICE as an example. The results show that for a power supply of +or-5 V, the nonlinearity error of the sample circuit is controlled to +or-0.3% over a +or-3-V input range. OTA (operational transconductance amplifier) parameters such as tuning capability, frequency response, and output impedance are examined. The body effect is considered. A second-order filter is presented as an application. >

Phase stable limiting power amplifier

Abstract: A phase stable limiting power amplifier includes a transistor, having a bias voltage applied to the collector and one applied to the base for operation in a class AB configuration. Input impedance matching circuitry may be coupled to the base with output impedance matching circuitry coupled to the collector. The input and output impedance matching circuitry may include only reactive elements for maximizing amplifier gain. Instability suppression circuitry may be connected between the base and the emitter. Representative functional characteristics for facilitating component selection and selection of operation conditions are provided.

Optimization of polysilicon emitters for BiCMOS transistor design

Abstract: Practical aspects of designing polysilicon emitters for large-scale integrated circuit manufacture are presented. It is shown that by choosing the emitter dose such that the minimum base saturation current density is observed, the highest product of common emitter gain and Early voltage is obtained. In practice, this allows high values of both parameters to be chosen, giving an increased bipolar output impedance. This reduces the need for elaborate Early voltage compensation during BiCMOS circuit design. In addition, the increase in the integrated base charge gives a reduction in the punched base resistance and hence the bipolar noise figure. The increase in the total base charge permits the use of a deeper, wider base region. Therefore, maximizing the product of common emitter gain and Early voltage gives transistors with optimized performance and improved reproducibility. >

Design Considerations for a Solar Array Switching Unit

Abstract: This paper presents an analysis of the sequential switching shunt regulator unit (SSU) proposed for the space station and space platform. The solar array and shunt regulator system is analyzed for ripple, output impedance, and stability. The performance of proportional gain and proportional-integrator (PI) controllers is compared. A design example is provided and an EASY5 simulation is presented for the regulation of the bus voltage by the SSU.

Judging method of life for stationary lead accumulator

Abstract: PURPOSE: To easily and accurately detect the service life of a battery by a method wherein an internal impedance of the battery is measured with different frequencies, each value of elements of an impedance equivalent circuit is calcu lated based on the measured impedance, and the calculated value is compared with an initial value, thereby to estimate the life of the battery. CONSTITUTION: An internal impedance equivalent circuit of a battery is formed in such relation as shown in the drawing among an inductance component L of a pole column, a strap, a grid body etc., an electrolyte resistance Rs, a capacity of an electric double layers Cd, a load moving resistance θ, and a Warburg impedance W and the like. A synthesizing impedance of the equivalent circuit calculates at least one value of the electric double layer capacity Cd, load moving resistance θ, Warburg factor and the like, and compares the calculated value with the corresponding initial value. Accordingly, the data related to the state of the battery such as the quantity of the effective reactive substance, surface area or the like can be properly estimated. The service life of the battery can be easily and accurately detected without measuring the discharge capacity of the battery. COPYRIGHT: (C)1992,JPO&Japio

Matching device in common use for antenna

Abstract: PURPOSE:To obtain an optimum selectivity by setting an optimum value of a variable capacitor of a primary circuit of a matching circuit. CONSTITUTION:A relay K4 is activated and a frequency from a transmitter 1 is detected, then a preset data set for each frequency is read from a memory 9 and a motor control circuit 8 presets capacitors C1-C4. A load detector 4 and a phase detector 5 adjust the capacitors C1, 2 to activate relays K1-3, and a transmission output is inputted to a secondary, circuit to adjust the capacitors C3, 4, thereby matching the secondary circuit and the transmitter 1. The processing above is repeated alternately and the primary and secondary circuits of the matching circuit 2 respectively converge the output impedance of the transmitter 1 and the impedance of a pseudo load R, thereby completing the matching to the load R. The antenna 6 is matched with the secondary circuit by adjusting the capacitors C3, 4 based on a signal from the detectors 4, 5 with the relays K1-4 inactivated, thereby matching the transmitter 1 and the primary circuit. Thus, optimum selectivity is obtained.

A high-frequency GaAs transductance circuit and its applications

Abstract: The design of a high-speed, linear, tunable operational transconductance amplifier (OTA) with 1 mu m GaAs depletion-mode MESFETs is described. Gain-enhancement techniques are used for obtaining high output impedance. In order to achieve a large tuning range with stable DC bias, a combination of digital and analog tuning is used. Diode-only level-shifting stages and bypass capacitors across the diodes are used to optimize the AC response. Emitter degeneration along with small compensation capacitors are used to achieve less than one percent nonlinearity error within a +or-0.4 V input range, and to reduce the total excess phase shift. Applications of the OTA in the GHz range are presented as examples. >

Surface electromyographic electrode pair with built-in buffer-amplifiers

Abstract: By means of a surface electrode with an operational amplifier, a new electrode unit suitable for an electromyographic-biofeedback apparatus and for portable electromyography used outside a Faraday cage was developed. The operational amplifier, which has an output impedance lower than 10 ohms, functions as an efficient buffer amplifier and is able to protect the EMG signals from background noises. This new electrode unit is small (32 × 12 × 5 mm), waterproof, and inexpensive. Because its structure is simple, it can be built in any laboratory.