An accurate technique for the direct measurement of the base spreading resistance of bipolar transistors

A method of determining the base spreading resistance of a bipolar transistor by measuring the noise exhibited by the transistor in a common emitter stage is described. This method proves to be very accurate, especially for high f_T devices. The technique is realizable for a large range of base resistances from 1 Ω to 2 kΩ and for collector currents of 10 μA to 10 mA. The technique described can be extended to extract the emitter bulk resistance, and additional methods can be applied for the extraction of the collector bulk resistance of the device. Thus, this method is particularly useful for the characterization of the intrinsic elements of the bipolar transistor. Once the exact value of the base spreading resistance is known it can be used as a reference, and the equivalent model of the bipolar transistor can be matched to the measured data in the frequency domain