AC Coupled Instrumentation Amplifier with Gyrators

Abstract

This paper investigates a method of excluding the input decoupling capacitors in an AC coupled instrumentation amplifier. The idea behind this paper is focusing mainly on reducing the silicon area when designing such amplifiers or the number of needed external components. Especially when the design requirements are pointed to low frequency operation but keeping AC coupling in the same time, the reactive components values may noticeably increase. As long as the GIC, Generalized Impedance Circuits, more specific the gyrators, are able to replace the capacitive and inductive behavior, they represent a good reason to study their applicability within instrumentation amplifiers. The gyrators are built around operational amplifiers so there will be a tradeoff between complexity in terms of transistor number and saved space by eliminating the capacitors at the input. The concept has been designed and validated based on simulation results using LtSpice.