New method to measure emitter resistance of heterojunction bipolar transistors

The null in third-order intermodulation as a function of emitter current in a bipolar transistor is exploited to find emitter Ohmic resistance. The measurement can be carried out using only low-cost equipment and a scalar receiver. Results for an heterojunction bipolar transistor (HBT) are compared with those found using a vector network analyzer and a sophisticated extraction algorithm. The method is extended to simultaneously determine thermal resistance, R/sub TH/, and to obtain a most precise estimate of emitter resistance.