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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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How to make a Rheostat

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Components

  1. The components needed for the connection are
  2. Flashlight bulb and socket [1]
  3. Dry cell lantern battery/D-cell battery [2]
  4. Wire [About 15 to 17 inches and another one 2 inches]
  5. Spring [1]
  6. Wire Clippers [A pair]
  7. A typical spring can be obtained from a widow roll up. You can even get to buy one at a cheap rate.

Procedure

  • Connect the two Dry cell lantern/D-cell batteries tail-to-tail, so that the positive polarity of one battery is connected to the negative polarity of the other.
  • Using a wire cutter, cut the wire in equal lengths. One wire should be at least 8 centimetres long.
  • Connect the wires onto the open ends of both the batteries.
  • The end of one wire must be connected to the bulb socket with the bulb in it.
  • Connect the second wire to one end of the long spring.
  • Connect the free end of one wire to one terminal of the light socket.
  • Connect the other free wire to one end of the spring.
  • Take the two inch wire and connect it to the second terminal of bulb socket.
  • Connect the other end of the two inch wire onto the other end of the spring.

 

What happens?

As soon as the circuit is in closed loop, the bulb begins to glow. Although the glow intensity is less, when you move the wire through the spring onto the other end where the wire is connected, the bulb starts to glow more brightly. When both the wires are nearby the glow will be in its maximum.
The spring is mainly made of steel wire. Steel wires are not very good conductors of electricity. Thus the resistance of the circuit also increases. If the spring length is long enough you will get to see different stages of the glow. Thus you will get to see the working of a rheostat.

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