The influence of diffusion current on the zero-tc point of a MOS transistor

Abstract

A special characteristic of a MOS transistor is that its drain current has a point somewhere around the threshold voltage where it almost doesn't vary with the temperature. This is called the Zero-TC (ZTC) point. By considering two different types of MOSFET models, a strong inversion and an unified one, it can see that both of them indicated the position of the ZTC point close to the measured one (sec Table 1). As this paper indicates, it is normally to presume that the larger value obtained with the unified model is due to the sub threshold component of the drain current. This is because the strong inversion model does not take it into account. Unlike this model, the unified one considers the drain current as a sum of the diffusion current, preponderant in weak inversion, and the drift current, which governs the strong inversion region. Because the ZTC point is somewhere between these two regions, it is normally to presume that the diffusion current has an influence on it. The paper will answer to this problem and will try to explain the results