Accurate and robust +or-nVT extractor

An accurate and robust +or-nV_T extractor is introduced. Basically, the circuit consists of a current comparator and a source follower. The output of the comparator controls the bias current level in the follower, and thus its low output resistance is divided by the loop gain providing high accuracy in most applications. The experimental results obtained using the commercial matched MOS transistor array TC4007 have been compared with the value obtained by classical methods and confirm the validity of the proposed circuit.