Simple derivation of a general sensitivity formula for lossless two-ports

A simple, yet comprehensive proof of an important sensitivity formula for lossless two-ports stated by Orchard, Temes, and Cataltepe is presented. Our derivation invokes the principle of conservation of energy and the lossless property of the network under consideration and employs the Cauchy-Riemann equations of complex differentiation. Hence, it bears clear physical interpretation and mathematical elegance.