Numerical calculations utilizing a realistic carrier velocity vs electric field relationship have been carried out for the dc current‐voltage characteristics and small‐signal ac response of abrupt Sip+np+,p+nvp+,n+pn+, andn+p&pgr;n+barrier injection transit time (BARITT) devices. The small‐signal ac response of these devices can be represented accurately by the depletion capacitance either in parallel with a negative conductance or in series with a negative resistance. The negative conductance has maximum amplitude for transit angles of approximately 1.55&pgr; and dc current density biases of 20–100 A/cm2. A distinct advantage was found in small‐signal applications forp+np+devices overp+nvp+devices and forn+pn+devices overn+p&pgr;n+devices.