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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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12v DC Fan Temperature Control

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Here is a simple circuit based on two transistors that can be acclimated to ascendancy the acceleration of a 12 V DC fan depending on the temperature.A thermistor (R1) is acclimated to faculty the temperature. When the temperature increases the abject accepted of Q1 (BC 547) increases which in about-face decreases the beneficiary voltage of the aforementioned transistor. Since the beneficiary of Q1 is accompanying to the abject of Q2 (BD 140), the abatement in beneficiary voltage of Q1 advanced biases the Q2 added and so do the acceleration of the motor. Also, the accuracy of the LED will be proportional to the acceleration of the motor.



Notes.
  • The R1 can be a 15K @ 20°C ,N.T.C thermistor.
  • The M1 can be a 12V,700mA fan motor.
  • The capacitor C1 must be rated 25V.
  • The circuit can be powered from a 12V PP3 battery or 12V DC power supply.
  • Assemble the circuit on a good quality PCB or common board.

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