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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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Doorbell circuit using NE555 IC

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The main part of this circuit Doorbell two timer NE555 ICs.When someone hit the switch S1 momentarily, the speaker emits a sound of the bell, if the time period of the monostable multivibrator built around IC1.


When the switch S1 pressed, IC1 is enabled in your pin 2 and pin 3 output is high for a period of time previously set by the values ​​of R4 and POT POT R5.When ofIC1 restores the IC2 output is high and starts to swing to make a bell sound through the speaker.The IC2 is configured as an astable multivibrator whose oscillation frequency can be varied with the help of POT R5.By adjusting the values ​​of R4 and R5, changes in tone are possible
Notes.
  • The circuit has to assembled on a good quality PCB or common board.
  • The IC1 & IC2 has to be mounted on IC holders.
  • Power the circuit from a 9V battery or 9V DC power supply.
  • Switch S1 is push button switch.

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