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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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20 WATT FLUORO INVERTER

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This circuit will drive a 40 watt fluoro or two 20-
watt tubes in series.
The transformer is wound on a ferrite rod
10mm dia and 8cm long.
The wire diameters are not critical but our
prototype used 0.61mm wire for the primary
and 0.28mm wire for the secondary and
feedback winding.
Do not remove the tube when the circuit is
operating as the spikes produced by the
transformer will damage the transistor.
The circuit will take approx 1.5amp on 12v,
making it more efficient than running the tubes
from the mains. A normal fluoro takes 20 watts
for the tube and about 15 watts for the ballast