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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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 The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal notion of "thickness". For example, honey has a higher viscosity than water . Viscosity is due to friction between neighboring parcels of the fluid that are moving at different velocities. When fluid is forced through a tube, the fluid generally moves faster near the axis and very little near the walls, therefore some stress (such as a pressure difference between the two ends of the tube) is needed to overcome the friction between layers and keep the fluid moving. For the same velocity pattern, the stress is proportional to the fluid's viscosity. A liquid's viscosity also depends on the size and shape of its particles and the attractions between the particles
A fluid that has no resistance to shear stress is known as an ideal fluid or inviscid fluid. In the real world, zero viscosity is observed only at very low temperatures, in superfluids. Otherwise all fluids have positive viscosity. If the viscosity is very high, such as in pitch, the fluid will seem to be a solid in the short term. In common usage, a liquid whose viscosity is less than that of water is known as a mobile liquid, while a substance with a viscosity substantially greater than water is simply called a viscous liquid.

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Shear viscosity

The shear viscosity of a fluid expresses its resistance to shearing flows, where adjacent layers move parallel to each other with different speeds. It can be defined through the idealized situation known as a Couette flow, where a layer of fluid is trapped between two horizontal plates, one fixed and one moving horizontally at constant speed u. (The plates are assumed to be very large, so that one need not consider what happens near their edges.)

The magnitude F of this force is found to be proportional to the speed u and the area A of each plate, and inversely proportional to their separation y. That is,
F=\mu A \frac{u}{y}
The proportionality factor μ in this formula is the viscosity (specifically, the dynamic viscosity) of the fluid.
The ratio u/y is called the rate of shear deformation or shear velocity, and is the derivative of the fluid speed in the direction perpendicular to the plates. Isaac Newton expressed the viscous forces by the differential equation
\tau=\mu \frac{\partial u}{\partial y}
where \tau = F/A and {\partial u}/{\partial y} is the local shear velocity. This formula assumes that the flow is moving along parallel lines and the y axis, perpendicular to the flow, points in the direction of maximum shear velocity. This equation can be used where the velocity does not vary linearly with y, such as in fluid flowing through a pipe.

Kinematic viscosity

The kinematic viscosity is the dynamic viscosity μ divided by the density of the fluid ρ. It is usually denoted by the Greek letter nu (ν). It is a convenient concept when analyzing the Reynolds number, that expresses the ratio of the inertial forces to the viscous forces:
Re = \frac{\rho u D}{\mu} = \frac{uD}{\nu}

Bulk viscosity

When a compressible fluid is compressed or expanded evenly, without shear, it may still exhibit a form of internal friction that resists its flow. These forces are related to the rate of compression or expansion by a factor σ, called the volume viscosity, bulk viscosity or second viscosity
The bulk viscosity is important only when the fluid is being rapidly compressed or expanded, such as in sound and shock waves. Bulk viscosity explains the loss of energy in those waves, as described by Stokes' law of sound attenuation.