Package and PCB Effects Shift Intermodulation Notch in an RF Common-Emitter Amplifier

A Taylor series analysis is conducted to study the effects of the package and printed circuit board (PCB) on the intermodulation nulling of an RF common-emitter amplifier. The equivalent parasitic element of the package and PCB interconnects is extracted from the impedance and admittance parameters, which are obtained using a three-dimensional (3-D) electromagnetic simulation tool. The theoretical analysis reveals that the effects of the package and PCB on the intermodulation nulling of commonemitter amplifiers is to shift the intermodulation notch; that the third-order intermodulation (IM3) products under an original bias condition cannot be suppressed and that the linearity of common-emitter amplifiers is thereby degraded. A comparison between theory and simulation reveals good agreement in the predicted locations of the intermodulation notch in the absence and presence of a package and PCB.