Approximate calculating methods concerning the electron transit time for avacuum microelectronics triode

We consider the approximate calculating methods of the electron transit tim e for a vacuum microelectronics (VME) triode, on the basis of comparison an d analysis of some results given by our predecessors. We summarize all the calculating methods of the electron transit time by four types-the method o f mean transit time, the method of average electric field, the method of th e equivalent electric field and the method of composite voltage. We discuss the common features of these four methods, unify all the calculating formu lae, draw some related curves for convenience to research and calculate new VME devices for use in the future.