Observations on the nonlinear behaviour of single and double InGaP/GaAs HBTs

Abstract

This paper explores the bias and voltage gain dependence of the small signal intermodulation distortion performance of the single and double InGaP HBT. It was found that the HBT has a zero in its 3rd order intermodulation distortion at low collector currents caused by the emitter resistance. The collector current at which this occurs can be approximately calculated with a simple formula. The small signal intermodulation distortion was little affected by collector voltage or voltage gain. There was very little difference between the small signal intermodulation distortion performance of the single and double HBT. Through a Volterra analysis it is demonstrated that the zero in 3rd order intermodulation distortion can be moved to a higher collector current by reducing emitter resistance.