Reduction of 1/f PM noise in BJT amplifiers with emitter feedback using compensation effects

Abstract

Investigation of 1/f PM and AM noise in bipolar junction transistor (BJT) amplifiers has shown that there are some opportunities to reduce 1/f PM noise in amplifiers using complex emitter feedback. But there was no systematic investigation of opportunities and limitations of this method of 1/f PM noise reduction. The aim of this paper is to present results of such an investigation. To solve the problem, a more general model of 1/f noise generation in BJT was used. Fluctuations both in recombination conductivity and base charging capacitance are taken into consideration. Two cases of compensation are considered. In the case of wideband compensation there is a wide frequency band where the reduction doesn't depend on the signal frequency /spl omega//sub s/. In the case of narrowband compensation there is a deep notch in dependence of 1/f PM noise power spectral density at each fixed Fourier frequency on /spl omega//sub s/. Limitations on the highest possible /spl omega//sub s/ at which compensation effect can be obtained are considered.