Patent ID: 7696817
Filing Date: 2010-04-13
Classification: H03F

Abstract:
1. An instrumentation amplifier having first and second differential instrumentation amplifier inputs and a differential instrumentation amplifier output comprising: first and second variable gain differential input amplifiers, each having a differential input, and having their differential outputs coupled to provide a common differential output; a third differential amplifier having a first capacitor coupled across its differential input, and having each of its differential outputs coupled to control the gain of a respective one of the first and second variable gain differential input amplifiers; first switches coupled to the common differential output to disconnect the common differential output of the first and second variable gain differential input amplifiers from the differential instrumentation amplifier output and couple the output of the first and second variable gain differential input amplifiers to the differential input of the third differential amplifier; second switches operative with the first switches to disconnect the first and second differential instrumentation amplifier inputs from the first and second variable gain differential input amplifier differential inputs, and to couple the differential inputs of the first and second variable gain differential input amplifiers to a single differential voltage with a polarity whereby the combined output is the difference in differential output of the first and second variable gain differential input amplifiers; whereby on momentarily operating the first and second switches, a voltage is stored on the first capacitor providing a differential output of the third differential amplifier correcting the differences in gain in the first and second variable gain differential input amplifiers.