The one-dimensional electroacoustic behavior of a uniform piezoelectric plate may be modeled by electrical equivalent circuits such as Mason or KLM models. Such models yield mathematically exact solutions to the governing equations, i.e., a set of constitutive equations and the differential equations of electrostatics and mechanics. In this article, we present an extension of the Mason equivalent circuit to the case of arbitrary nonlinear constitutive equations by the use of telegrapher's equations in a mathematically exact way. The resulting model consists of the original Mason circuit, distributed nonlinear voltage sources along its acoustic arm, and a nonlinear voltage source at the electrical terminal. We also show the proof that the circuit meets all the governing equations, and comparison of simulated results and harmonic measurements of FBAR devices. V C 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE 21:486-495, 2011.