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

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

Simple Programmable Amplifier Circuit Diagram

This is a Simple Programmable Amplifier Circuit Diagram, A programmable-gain amplifier (PGA) is an electronic amplifier (typically an operational amplifier) whose gain can be controlled by external digital or analog. Often a circuit will be called upon to perform several functions. In these situations, the variable gain configuration of this circuit could be quite useful. 

 Simple Programmable Amplifier Circuit Diagram


 Simple Programmable Amplifier Circuit Diagram


This programmable gain stage depends on CMOS analog switches to alter the amount of feedback, and thereby, the gain of the stage. Placement of the switching elements inside the relatively low current area of the feedback loop, minimizes the effects of bias currents and switch resistance on the calculated gain of the stage. 

Voltage spikes can occur during the switching process, resulting in temporarily reduced gain because of the make before- break operation of the switches. This gain loss can be minimized by providing a separate voltage divider network for each level of gain.

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