In this paper, we discuss the various factors affecting the Ic-VBE characteristics of a transistor in the low injection level, i.e. the factors to change n*≡ d(VBE/VT)/dlnIc to departe from 1. It is described also an accurate differential method of measuring n* for integrated transistor-pair. We show that the quasi-Fermi potential drop in emitter junction is an important factor in the explaination on the case n*< 1 observed in some transistors.