Translinear circuits: An historical overview

The concept of a translinear circuit is now widely appreciated and applied. This paper traces the history of the concept, delineates the original meaning of the term, explains the basic principles of this class of circuit and discusses recent, more general, interpretations of the term. It is recommended that the word translinear, used without further qualification, should be reserved exclusively for those cells invoking exponential device behaviour, which applies to all bipolar transistors, including heterojunction types, and to MOS transistors operated in the subthreshold, or weak inversion, domain, but does not apply to normal MOS operation in strong inversion. It is proposed that the theory and practice related to such 'quadratic' operation of MOS devices, where the transconductance is presumed to be linear with gate-source voltage, should be termed voltage-translinear, or VTL.