Automated design of operational transconductance amplifiers using reversed geometric programming

Abstract

We present a method for designing operational amplifiers using reversed geometric programming, which is an extension of geometric programming that allows both convex and non-convex constraints. Adding a limited set of non-convex constraints can improve the accuracy of convex equationbased optimization, without compromising global optimality. These constraints allow increased accuracy for critical modeling equations, such as the relationship between gm and IDS . To demonstrate the design methodology, a foldedcascode amplifier is designed in a 0.18 µm technology for varying speed requirements and is compared with simulations and designs obtained from geometric programming.

CMOS op-amp power optimization in all regions of inversion using geometric programming

“…That is, including the weak inversion region and, specially, the moderate inversion region where optimal designs usually are. This was also observed in the third work [4], where a complete model valid in all regions of inversion was used [6].…”

“…According to how the circuit performance and constraints are evaluated during optimization, the tools can be broadly classified in simulation-based optimization and equation-based optimization [1][2][3][4].…”

“…The disadvantage is that design equations must be formulated in a posynomial form (see Section 2), which is not always the case in analog design. These methods have been used quite recently applied to the problem of CMOS opamp design [2][3][4].…”

“…To overcome these problems, [4] incorporates a branch and bound algorithm to its convex optimization method, and thus, looses part of its advantages.…”

Digital Circuit Optimization via Geometric Programming

“…Other problems in digital circuit design where GP plays a role include buffering and wire sizing Wong 1999, 2001a), sizing and placement (Chen et al 2000), yield maximization , Patil et al 2005, parasitic reduction (Qin and Cheng 2003), clock tree design (Vittal and Marek-Sadowska 1997), and routing (Borah et al 1997). Geometric programming has also been used for the design of nondigital circuits, e.g., analog circuits (Dawson et al 2001, Hershenson 2003, Hershenson et al 1998, Mandal and Visvanathan 2001, Vanderhaegen and Brodersen 2004, mixed-signal circuits (Colleran et al 2003, Hassibi and Hershenson 2002, Hershenson 2002, and RF (radio frequency) circuits Mohan et al 1999Mohan et al , 2000Xu et al 2004). Geometric programming has also been used in floorplanning, for both analog and digital circuits (Moh et al 1996).…”