The operational amplifier (hereafter OP-AMP)is developed in the 1940s primarily for use in analog computers, made cheaply and readily available in the late 1960s through integrated-circuit technology. The actual construction of a modern OP-AMP is indeed very complex, involving many transistors, diodes, resistors and capacitors
Mesh analysis is applicable only to those networks, which are planar. If it is possible to draw the diagram of a circuit on a plane surface in such a way that no branch passes over or under any other branch, then that circuit is said to be planar circuit. (Non-planar-circuit