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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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Simple Portable Nicad Battery Charger Circuit Diagram

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This is a Simple Portable Nicad Battery Charger Circuit Diagram. This Simple Portable Nicad Battery Charger Circuit Diagram was designed to charge NiCad battery packs in the range of 4.8 to 15.6 V from a convenient remote power source, such as an automobile batter. 



Portable Nicad Battery Charger Circuit Diagram

When power is first applied to the circuit, a small bias current supplied by Rl via winding Wl, starts to turn on the transistor TRl. This forces a voltage across W2 and the positive feedback given by the coupling of Wl and W201uses the transistor to turn hard on, applying the full supply across W2. The base drive voltage induced across Wl makes the junction between Rl and R2 become negative with respect to the 0-V supply, forward-biasing diode Dl to provide the necessary base current to hold TRl on. 

With the transistor on, a magnetizing current builds up in W2, which eventually saturates the ferrite core of transformer Tl. This results in a sudden increase on the collector current flowing through TRl, causing its collector-emitter voltage to rise, and thus reducing the voltage across W2. 

The current flowing in W2 forces the collector voltage of the TRl to swing positive until restricted by transformer output loading. Rc network R4 and C3limits the turn off transient TRl. R3 and C2 maintain the loop gain of the circuit when diode Dl is not conducting.

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