T-Shaped association of transistors: Modeling of multiple channel lengths and regular associations

This work presents an analysis of a new type of composite transistor specially suited for the design of analog integrated circuits: the T-shape association of transistors. This association is composed by non-equal size unit transistors arranged in a series-parallel array with common gate, which can substitute the conventional rectangular transistors with advantages in some aspects, such as better high-frequency performance, lower output conductance and layout regularity. Dedicated tools that automatically translate the single transistors into equivalent associations without degradation in the overall circuit specifications guarantee the compatibility with the conventional analog design methodology. Some properties and applications are discussed in this paper. Experimental and simulated characteristics are shown in order to verify the behavior of the association.