Getting the most out of your instrumentation amplifier design

摘要

Many industrial and medical applications use instrumentation amplifiers (INAs) to condition small signals in the presence of large common-mode voltages and DC potentials. Standard INAs using a unity-gain difference amplifier in the output stage, however, can limit the input commonmode range significantly. Thus, commonmode signals induced by adjacent equipment, as well as large differential DC potentials from differently located signal sources, can increase the input voltage of the INA, causing its input stage to saturate. Saturation causes the INA output voltage, although of wrong value, to appear normal to the following processing circuitry. This could lead to disastrous effects with unpredictable consequences.