Exploring a new method for improving dynamic range of instrumentation amplifier for processing low voltage signals

The paper explores a new technique for improving dynamic range of instrumentation amplifier which is most commonly used signal processing device. The method which improves the dynamic range by blocking undesirable input DC offset voltages without use of conventional RC components [1] is free from the errors produced due to their finite tolerances which erroneously convert a part of common mode AC signal into differential signal resulting in to degradation of CMRR of instrumentation amplifier. The mathematical analysis of the circuit based on this method is given in the paper which shows that the loss of dynamic range due to differential DC voltages at input is reduced only to a small common mode voltage. The relationship is expressed in form of new theorem proposed in the paper named as theorem of dynamic range recovery for instrumentation amplifier. Experimental results are obtained using simulation which shows agreement with derived/expected results. Effect of finite source impedances as well as distortion at low frequencies in conventional R-C coupling is also eliminated. Using this method the improvement in CMRR by a factor of more than 1000 could be obtained as compared to one using conventional R-C coupling circuits with 10% tolerance components.