In this paper, we study the bipolar transistor characteristic matching in all current ranges. At low current, the phenomena responsible of the base current mismatch degradation are interpreted and a new base current mismatch model is derived. At medium current, the physical origins of the mismatch in bipolar transistors are investigated leading to new mismatch models. Moreover, matching performances of Si/SiGe(:C) heterojunction bipolar transistors, processed in several BiCMOS technologies, are characterized and compared. In the high current region, the impact of the emitter resistance mismatch on the base and the collector current mismatch degradations is fully demonstrated. (c) 2007 Elsevier Ltd. All rights reserved.