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SUMMARYThis paper presents an integrated approach of simulated annealing (SA) and genetic algorithm (GA) for the analogue module placement in mixed-signal integrated circuit layout designs. The proposed algorithm follows the optimization ow of a normal GA controlled by the methodology of SA. The bitmatrix chromosomal representation is employed to describe the location and the orientation of modules. Compared with the conventional bit-string representation, the proposed chromosomal representation tends to signiÿcantly improve the search e ciency. In addition, a slide-based at scheme is developed to transform an absolute co-ordinate placement of modules to a relative placement. In this way, the symmetry constraints imposed on analogue very large scale integration circuits can be easily fulÿlled in the placement run. Use of a radiation-decoder can also drastically shrink the conÿguration space without degrading search opportunities. The proposed algorithm has been tested with several example circuits. The experiments show this promising algorithm makes the better performance than the simpler SA or GA approaches working alone, and the quality of the automatically generated layouts is comparable to those done manually.

Current transfer function is a feature of current‐mode filters. Current‐mode filters have so far been realized principally using current amplifiers and current conveyors. Some current‐mode filter architecture using operational amplifiers have also been reported. In this article it is shown that by using the principles of transposed network and nullor model for the active device, a current transfer function can be realized in a very simple way using a voltage amplifier, i.e. operational amplifier (OA). The key concept is the knowledge that each ideal (i.e. infinite gain) controlled source is exactly equivalent to a nullor. Thus, a voltage‐mode filter implemented using an ideal three terminal (output, input and ground) OA can be very easily converted to a current‐mode filter using the same OA. The principle has been illustrated by considering single‐OA‐ and multi‐OA‐based second‐order voltage‐mode filters. SPICE simulation results are provided to validate the theoretical concept. Copyright © 2006 John Wiley & Sons, Ltd.

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