An asymmetrical bulk-modified composite MOS transistor with enhanced linearity

A Self-biased Current Source, using an Asymmetric Bulk-modified MOS Composite Transistor

“…1 and also in Fig. 2, showing the extended linear range and 'saturation' effects as described in [1], [2]. In Fig.…”

“…1 two transistors are connected as a MOS divider to bias the bulk of the selftransistors, defining the equivalent transistor Meq with its own Source (S), Gate (G), Drain (D) terminals; the equivalent bulk terminal is not defined for Meq. As pointed in [1], [2], Meq shows an enhanced linear region, where the best results are obtained when the aspect ratios (W/L)a of Ma and (W/L)b of Mb are very different (W/L)a >> (W/L)b. Depending on the transistors' sizes, the resulting composite structure is linear up to an equivalent saturation VSat_eq voltage of a few hundred mV like in Fig.…”

“…A bulk-linearization technique was presented in [1] to enhance the linearity of the MOS transistor, using two series MOSFETs like in Fig. 1; later in [2] this composite structure was examined as a new composite transistor. In Fig.…”

“…1. Because (W/L)a ¹ (W/L)b the new composite transistor will be denoted as an asymmetrical bulk-modified transistor or ABM-MOS, and allows to build basic structures like differential pairs or current mirrors [2], to emulate large resistors [1], or exploiting its behavior to implement basic building blocks with a transfer function otherwise difficult to obtain, enabling a new family of circuits. In this work, a simple self-biased current reference in CMOS technology is presented, based in the characteristics of an ABM composite transistor.…”