Topic
Output impedance
About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.
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TL;DR: In this paper, the authors proposed an approach to solve the problem of alternating current (AC) impedance sensing of particles (e.g., blood cells in plasma) with micro electrodes, where they used resonant sensing by connecting an external parallel inductor to the system.
Abstract: A challenging problem in alternating current (AC) impedance sensing of particles (e.g., blood cells in plasma) with micro electrodes is that
with the shrinking of electrode surface area the electrode double layer capacitance decreases. This double-layer capacitor dominates the system
impedance in lowfrequency range, while the parallel stray capacitor dominates the system impedance in high frequency range. Hence the sensitivity
for particle sensing for micro impedance sensors decreases over a wide frequency range. In this paper, we propose an approach to solve the problem.
The idea is to use resonant sensing by connecting an external parallel inductor to the system. At the resonant frequency, the capacitive components
in the system are nullified by the inductor, leaving the channel impedance (including the particle impedance) to be a major component in the system
impedance. We then successfully demonstrate this idea by sensing 5 µm polystyrene beads. More important, this technique is extended to sensing
blood cells in diluted human whole blood and leukocyte-rich plasma. The sensitivity can be improved by two orders of magnitude over more than
three decades in frequency domain. The measured signal peak height histogram at low frequency matches well with known volume distribution of
erythrocytes and leukocytes.
36 citations
TL;DR: This work has developed α 1.5 mm2 porous, platinized, steroid‐eluting electrode and has demonstrated in canine studies that it has excellent performance and sensing, with almost double the P wave amplitudes usually measured in the canine.
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.
36 citations
TL;DR: A CMOS operational amplifier (OPAMP) for use as a line driver for high-speed T1/E1 data communication link is described, achieving a unity-gain bandwidth of 35 MHz with only 10 mA of quiescent current.
Abstract: A CMOS operational amplifier (OPAMP) for use as a line driver for high-speed T1/E1 data communication link is described. The differential output swing, using a single 3.3-V power supply, is 5.2-V peak-to-peak on a 20-/spl Omega/ load. Novel circuits are used to control the closed-loop output impedance, quiescent bias current, and frequency compensation to ensure stable operation over varying temperature and load conditions. A special circuitry tristates the output in case of power-supply failure. The OPAMP achieves a unity-gain bandwidth of 35 MHz with only 10 mA of quiescent current. A new output-current-sense circuitry is used to provide a current feedback to adjust the output impedance for proper line termination as well as to provide short-circuit protection from excessive output currents. Using 0.35-/spl mu/m n-well CMOS technology, the amplifier occupies 0.69 mm/sup 2/ of area.
36 citations
TL;DR: In this paper, a discrete-time model describing the dynamic electrical behaviour of the fuel cell is depicted as an equivalent circuit which consists of a voltage source and the impedance as internal resistance.
36 citations
TL;DR: In this paper, an interface circuit designed for the measurement of impedance parameters of sensors or measurement cells installed on technical objects has been presented, which is based on two specialized SoC AD5933 microsystems.
Abstract: The paper presents an interface circuit designed for the measurement of impedance parameters of sensors or measurement cells installed on technical objects. The interface circuit allows measurement of the modulus and argument of impedance in the range of 10 Ω ≤ |Zx| ≤ 10 GΩ at a measurement frequency in the range of 0.01 Hz to 100 kHz. The new solution based on two specialized SoC AD5933 microsystems has been used. This has allowed to obtain miniaturization, low power consumption and low-cost of the circuit of the impedance interface. During tests of the realized prototype using the reference object, the object impedance measurement errors have been determined and they do not exceed ±1.6% (for relative error of impedance modulus) and ±0.6° (for absolute error of impedance argument). The obtained accuracy is fully acceptable in case of impedance measurement of anticorrosion coating in the field. The comparison measurements performed with the aid of Solartron set of instruments showed that the impedance measurement accuracy of the proposed module is comparable to laboratory set of instruments. The important advantage of the used solution based on AD5933 microsystems is lowering the power consumption down to ca. 0.7 W, which makes possible powering the measurement module from a PC using +5 V from the USB. It is a very profitable feature for a module designed to work directly in the field.
36 citations