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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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Simple Adjustable Notch Filter Circuit Diagram

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Adjustable Notch Filter Circuit Diagram. In applications where the rejected signal might deviate slightly from the null on the notch network, it is advantageous to lower the Q of the network. This insures some rejection over a wider range of input frequencies. The figure shows a circuit where the Q may be varied from 0.3 to 50. A fraction of the output is fed back to R3 and C3 by a second voltage follower, and the notch Q is dependent on the amount of signal fed back. A second follower is necessary to drive the twin `T` from a low-resistance source so that the notch frequency and depth will not change with the potentiometer setting.

Adjustable Notch Filter Circuit Diagram


 

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