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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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LIGHT EXTENDER

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This circuit is a Courtesy Light Extender for cars. It
extends the "ON" time when a door is closed in a
car, so the passenger can see where he/she is
sitting.
When the door switch is opened, the light normally
goes off immediately, but the circuit takes over and
allows current to flow because the 22u is not
charged and the first BC 547 transistor is not
turned ON. This turns on the second BC547 via the
100k and the BD679 is also turned on to illuminate
the interior light.
The 22u gradually charges via the 1M and the first
BC547 turns on, robbing the second BC547 of
"turn-on" voltage and it starts to turn off the BD679.
The 1N4148 discharges the 22u when the door is
opened.