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The design of analog integrated circuits together with mixedsignal applications in deep sub-micron technologies is a difficult task, since state-of-the-art technologies and minimum channel length transistors, suitable for digital circuits, are very rarely optimized for analog block design. Non-desired effects are presenting in the shortest transistors, leading mainly to a high output conductance, which is disadvantageous for DC voltage gain stages. We present measurement results supporting the associations of transistors concept to be used in such applications: the T-Shaped Transistor (TST) [1]. The main characteristic of this association is its trapezoidal nature, with no limit on the sizes of the unit composite transistors, providing lower output conductance and saturation voltage in comparison to regular configurations. Such electrical characteristics are demonstrated by means of electrical simulations and electrical measurements of a test chip fabricated by MOSIS in an IBM 0.18µm CMOS process.

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.