Ponencia presentada en el XIX Congreso Internacional de Acústica (ICA2007), Madrid, 2-7 Sep 2007.-- PACS: 43.38 Fx, 43.35 Zc, 43.35-c.The design of efficient ultrasonic transceivers systems for imaging and detection is having a great development at the present time. These systems have demonstrated a great utility in important tasks concerned with the medical and industrial diagnosis. In this paper we present a review and analysis of several Equivalent Circuital Models, proposed for us with the aim of simulating the responses of wideband ultrasonic transceivers, including their piezoelectric, electronic and ultrasonic sections. Modelling of important aspects present in practical configurations, used for medical and industrial diagnostic, are included: Non-linear effects in the emitting-receiving circuits; Non-ideal aspects on the loss and electrical distortions in the electronics; Frequency behaviour of the mechanical losses in the piezoceramic and the propagation medium. Some of the models proposed employ accurate estimated data for the piezoelectric transducers internal parameters. These data were obtained with a new estimation procedure here considered, based on Genetic Algorithms (GAs). PSPICE implementations of these models are presented for simulation in the temporal domain of Through-Transmission (T/T) and Pulse-Echo (P/E) configurations belonging to different imaging dispositions, which consider high-voltage regime and with the real circuital topologies used in the electronic transceivers. Comparison with the experimental data shows a clear improvement in the accuracy of these new models.This work has been supported by the Spanish MEC, R&D Project CICYT Ref. DPI2005-00124 of the I+D National Plan.Peer reviewed