New pi-model of bipolar transistor noise for circuit analysis and simulation and technique to reduce phase noise in bipolar oscillators

A new bipolar transistor noise model for SPICE and SPICE based simulation software is introduced. The parameters of the new bipolar transistor noise model are predicted using MATLAB and the results are compared with measurement results. The new model avoids the unreal situation in the current model where the transistors will have no 1/f noise in the collector current output if the impedance in the base circuit is small. Low frequency feedback is utilized to reduce the effect of base-emitter current 1/f noise in bipolar transistor oscillators. A resistance in the emitter that is bypassed at the higher oscillation frequency but not at the lower 1/f noise frequency will reduce the nonlinear mixing of the two current signals and phase noise in oscillator. The concepts are demonstrated by a simple low frequency oscillator.