1/F AM and PM noise in bipolar transistor amplifiers: Sources, ways of influence, techniques of reduction

The results of theoretical and experimental work, aimed to find fairly good model of 1/f noise sources that could help to explain experimental data and show the ways to reduce 1/f AM and PM noise caused by bipolar transistor amplifiers are presented. It is shown that the noise model of BJT in which relative 1/f fluctuations of recombination current are considered as the main source of fluctuations is in good agreement with experiment. Basing on hybrid pi BJT model with fluctuating recombination conductance an approach to AM and PM noise calculations in BJT amplifier was developed. An influence of biasing circuits, collector junction capacitance, unbypassed emitter resistance, emitter inductance on 1/f AM and PIM noise added by CE amplifier is considered. An effect of 1/f PM noise compensation in the amplifier with properly chosen RC-circuit in emitter lead is revealed. Recommendations for decreasing of 1/f AM and PM noise of BJT amplifiers are formulated.