PM and AM noise in nonlinear BJT amplifier

An approach to nonlinear BJT amplifier PM and AM noise calculation is presented. Polyharmonic presentation of voltages and currents is used and periodical nonstationarity of BJT noise sources due to their modulation by periodic signal is taken into consideration. Due to these effects one has to introduce different "noise factors" for PM and AM noise calculation (if one expands the formulae obtained for linear mode of operation to nonlinear one), and these noise factors depend on the input signal level. Common emitter (CE) amplifier with both bypassed and unbypassed resistors in emitter circuit is considered in detail. Power spectral densities of AM and PM noise are calculated as functions of signal amplitude. An influence of bypassed and unbypassed emitter resistor on PM and AM noise is investigated.