Compound operational amplifiers

The choice of a low-noise voltage operational amplifier (VOA) for a particularly stringent application often results in a restrictive compromise between accuracy, bandwidth, and cost. This compromise can be avoided by combining two individual VOAs together in such a manner as to form a single compound operational amplifier device. This work concerns a particular technique for combining two VOAs into a composite which exhibits the premium behaviour from each of the constituent units, with the low frequency performance of one VOA and the high frequency properties of the other. The composite can be treated just like a conventional VOA and is not confined to virtual earth applications