A new model for the low-frequency noise and the noise level variation in polysilicon emitter BJTs

Presents a new, physically-based model for the low-frequency noise in high-speed polysilicon emitter bipolar junction transistors (BJTs). Evidence of the low-frequency noise originating mainly from a superposition of generation-recombination (g-r) centers is presented. Measurements of the equivalent input noise spectral density (SIB) showed that for BJTs with large emitter areas (AE) S(I_B) is proportional to 1/f, as expected. In contrast, the noise spectrum for BJTs with submicron A_E showed a strong variation from a 1/f-dependence, due to the presence of several g-r centers. However, the average spectrum ⟨S(I_B)⟩ has a frequency dependence proportional to 1/f for BJTs with large as well as small A_E. The proposed model, based only on superposition of g-r centers, can predict the frequency-, current-, area-, and variation-dependency of ⟨S(I_B)⟩ with excellent agreement to the measured results