Square-rooting and absolute function circuits using operational amplifiers

A method for implementing square-rooting and absolute function circuits using operational amplifiers (opamps) as only active elements is introduced. The realisation technique is provided through the use of the opamp supply-current sensing, which utilises an inherently quadratic characteristic of the opamp class-AB output stage. The proposed circuits are attractive in terms of simple configuration and low cost. The performances of the circuits are discussed in detail. Experimental results demonstrating the characteristics of the circuits using commercially available opamps are also included.