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High CMRR Instrumentation Amplifier (Schematic and Layout) design for biomedical applications

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Instrumentation amplifiers are intended to be used whenever acquisition of a useful signal is difficult. IA’s must have extremely high input impedances because source impedances may be high and/or unbalanced. bias and offset currents are low and relatively stable so that the source impedance need not be constant. Balanced differential inputs are provided so that the signal source may be referenced to any reasonable level independent of the IA output load reference. Common mode rejection, a measure of input balance, is very high so that noise pickup and ground drops, characteristic of remote sensor applications, are minimized.Care is taken to provide high, well characterized stability of critical parameters under varying conditions, such as changing temperatures and supply voltages. Finally, all components that are critical to the performance of the IA are internal to the device. The precision of an IA is provided at the expense of flexibility. By committing to the one specific task of
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Antialiasing And Sync-Compensation Filter Circuit Diagram

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Antialiasing And Sync-Compensation Filter Circuit Diagram. Two dual-bi-quad filter chips and some external components form a multipurpose filter to reconstruct D/A converter signals. Connected to a converter`s output, the filter provides anti-aliasing, reduces the D/A converter`s quantization noise, and compensates for sin(7rx)()—the `sync` function (attenuation). The circuit incorporates an inverse-sync function that operates to one-third of the converter`s sample rate. Beyond one-third, the filter`s response shifts to a stop band filter, which provides -70 dB attenuation. 

This attenuation conforms to the converter`s inherent signal-to-noise ratio and quantization error. To prevent aliasing, the stop band edge must be no higher than the Nyquist frequency (/„ + 2). To achieve 70-dB stop band rejection with this eighth-order filter requires a transition ratio (/stop band -K/pass band) of 1.5, which sets the passband`s upper limit at fs +3. Notice also that you can apply a simple divide-by-64 circuit to the 192-kHz clock frequency to set the necessary 3 ratio between the converter`s sample rate and the filter`s 1-kHz corner frequency. 

Antialiasing And Sync-Compensation Filter  Circuit Diagram

Antialiasing And Sync-Compensation Filter Circuit Diagram
 

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