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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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Build a Tone Burst Generator Circuit Diagram

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Build a Tone Burst Generator Circuit Diagram. This is a simple Tone Burst Generator Circuit Diagram. The tone burst generator supplies a tone for one-half second after the power supply is activated; its intended use is a communications network alert signal. Cessation of the tone is accomplished at the SCR, which shunts the timing capacitor CI charge current when activated. 

The SCR is gated on when C2 charges up to the gate voltage which occurs in 0.5 seconds. Since only 70 ?? are available for triggering, the SCR must be sensitive enough to trigger at this level.The triggering current can be increased, of course, by reducing R2 (and increasing C2 to keep the same time constant). 




If the tone duration must be constant under widely varying supply voltage conditions, the optional Zener diode regulator circuit can be added, along with the new value for R2 R2' = 82 kfi. If the SCR is replaced by an npn transistor, the tone can be switched on and off at will at the transistor base terminal.

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