Analysis of a transistor delayed injection and transit time device is given in this paper. Its configuration is similar to a conventional transistor with the exception of the addition of a v or π layer （transition region） between collector and base regions and it is operated as a diode. The negative resistance and the noise performances are calculated by means of small signal theory. The large-signal performances are also approximately described. It is shown that output power about one watt as well as fairly high efficiency can be obtained at X-band

whereas the measured noise is about 20dB smaller than that of IMPATT.