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High CMRR Instrumentation Amplifier (Schematic and Layout) design for biomedical applications

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

TRANSISTOR TESTER


The 555 operates at 2Hz. Output pin 3 drives the circuit with a positive
then zero voltage. The other end of the circuit is connected to a voltage
divider with the mid-point at approx 4.5v. This allows the red and green
LEDs to alternately flash when no transistor is connected to the tester.
If a good transistor is connected, it will produce a short across the LED
pair when the voltage is in one direction and only one LED will flash. If the
transistor is open, both LED’s will flash and if the transistor is shorted,
neither LED will flash.