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Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
The input impedance of an op-amp circuit can be found by applying a test voltage source across the input port and measuring the current that flows into the port. The applied voltage divided by the resulting current is the input impedance. (When computing the output impedance, the input source(s) must be TABLE 115.1 Typical Op-Amp Specifications
Giga-Ohm High-Impedance FET Input Amplifiers for Dry Electrode Biosensor Circuits and Systems
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
Gaetano Gargiulo, Paolo Bifulco, Rafael A. Calvo, Maria Romano, Mariano Ruffo, Richard Shephard, Mario Cesarelli, Craig Jin, Alistair McEwan, André van Schaik
The preamplifier stage is the crucial element of a biopotential measurement system; its main tasks are twofold: first, to sense the microvolt-level voltage between two measuring electrodes while rejecting the common-mode signal; second, by minimizing the dc effect of electrode polarization overpotentials. These unwanted signals are typically three to four orders of magnitude greater than the biopotential of interest demanding a CMRR of greater than 60 dB. Crucial for maintaining the performance of the preamplifier in practice is the input impedance, which should be as high as possible. Typical specifications include an input impedance of greater than 100 mega-ohms. Such a differential amplifier cannot be realized using a standard single operational amplifier (op-amp) design since this does not provide the necessary combination of high input impedance, CMRR, and gain over the required frequency range [2,4].
Facility Grounding
Published in Jerry C. Whitaker, Electronic Systems Maintenance Handbook, 2017
Adding a pair of buffer amplifiers before the summing stage results in an instrumentation-grade circuit, as shown in Fig. 15.77. The input impedance is increased substantially, and any source impedance effects are eliminated. More noise is introduced by the added op-amp, but the resistor noise usually can be decreased by reducing impedances, causing a net improvement in system noise.
Application of Behavioral Psychology in Clothing Design from The Perspective of Big Data
Published in Applied Artificial Intelligence, 2023
The characteristics of the behavioral psychological ECG signal source are high internal resistance and small amplitude, which requires the input impedance of the amplifier to be high enough. If the input impedance is not high enough compared to the source impedance, it will cause the amplitude of the signal component entering the differential amplifier to decrease. At the same time, under the condition of large input impedance, the stability of the amplification factor will be reduced due to the error of the impedance in front of the amplifier input. The customizable logic block (CLB) matrix at the center of Field Programmable Gate Arrays (FPGAs), a semiconductor device, is coupled by programmable interconnects. After production, FPGAs can be reprogrammed to meet specific application or feature needs. While developing application-specific integrated circuits or processor prototypes, FPGAs are especially helpful.