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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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Overload Speaker Protection Circuit Diagram

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Overload Speaker Protection Circuit Diagram input is taken from the terminal loudspeaker or amplifier output jacks. If the right channel is large enough to charge C1 to a potential which exceeds the breakdown voltage of the emitter of Ql, a voltage pulse appears in R7. Similarly, if the left channel signal is large enough to charge C2 to a voltage that is greater than the breakdown voltage of the emitter of Q2 `, a pulse appears in R7. The pulse triggers in R7 5CRI. A door sensitive SCR (LGT less than 15 RNA or IGT is the gate-trigger current) that locks in a conducting state and energizes Ryl. The action of the relay will interrupt the speaker circuit. and silence follows you must alert on the problem. 

 Overload Speaker Protection Circuit Diagram

Overload Speaker Protection Circuit Diagram


Reduce the volume on your amplifier, then press and release 51 to reset the circuit and restore normal operation. The circuit can be set to go off at any level of 15 watts RMS to 150. To calibrate . deliberately over-power signal at the entrance of the right speaker protection and adjust R3 until RY1 boosts. Do the same with the left channel, this time adjusting R4. The circuit is now calibrated and ready employment.

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