ANALYSIS OF A COMPOSITE AMPLIFIER TECHNIQUE FOR OPTIMUM NOISE PERFORMANCE

A technique for combining two voltage-operational amplifiers to create a single composite-voltage operational amplifier (VOA) is analysed. T he composite amplifier can be treated essentially as a single VOA whic h gives an optimum combination of the DC and AC performances of the tw o constituent amplifiers. Specific practical examples of the technique have been previously reported, but in this paper we present an analys is and establish the optimum combination conditions. To support the an alysis a further example of the composite technique is presented in wh ich a high-performance chopper-stabilised VOA (MAX 430) is coupled wit h a low-noise bipolar VOA (OP 27). Measurements have shown that the co mposite device exhibits premium qualities from both OA, with low noise and very low input-offset voltage drift.