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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

Safe Constant Current Source Circuit Diagram

In the Safe Constant Current Source Circuit Diagram shown, a CMOS op amp controls the current through a p-channel HEXFET power transistor to maintain a constant voltage across RL The current is given by: 1 ~ VREF/Rl. The advantages of this configuration are: (a) in the event of a component failure, the load current is limited by Rl; and (b) the overhead voltage needed by the op amp and the HEXFET is extremely low.


Safe Constant Current Source Circuit Diagram

Safe Constant Current Source Circuit Diagram

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