Automatic design of analog circuits using a programmed algorithm is in great demand because optimal analog circuit design in a short time is required due to the limited development time. Although an automatic design using equation-based method can design simple circuits fast and accurately, it cannot solve complex circuits. On the other hand, an automatic design using optimization algorithm such as Ant Colony Optimization, Genetic Algorithm, and so on, can design complex circuits. However, because these algorithms are based on the stochastic optimization technique and determine the circuit parameters at random, a lot of circuits which do not operate in principle are generated and simulated to find the circuit which meets specifications. In this paper, to reduce the search space and the redundant simulations, automatic design using both equation-based method and a genetic algorithm is proposed. The proposed method optimizes the bias circuit blocks using the equation-based method and signal processing blocks using Genetic Algorithm. Simulation results indicate that the evaluation value which considers the trade-off of the circuit specification is larger than the conventional method and the proposed method can design 1.4 times more circuits which satisfy the minimum requirements than the conventional method.

Circuit access control is a traffic control technique of rejecting calls arriving at a group of specified circuits to make the group free at a target scheduled time so that the capacity may be dynamically reallocated to serve other traffic demand. This technique plays an important role for resource allocation control in state-of-the-art capacity reconfigurable networks as well as for switching calls on a reserved basis in the ISDNs. In this paper, we present a novel adaptive scheme for circuit access control in order to overcome the inefficiency of the conventional deterministic scheme. The presented scheme is based only on knowledge about service time and bandwidth characteristics of calls. The transitional behavior of the circuit group under the scheme is analyzed, and the gain in utilization achieved by the adaptive scheme is examined. We treat a model of the circuit group shared by multi-slot calls with different service times, and describe the results of the transient analysis and the approximation method for evaluating the gains.

Recent achievements in low-voltage and low-power circuit techniques are reported in this paper. DC current in low-voltage CMOS circuits stemming from the subthreshold current in MOS transistors, is effectively reduced by applying switched-power-line schemes. The AC current charging the capacitance in DRAM memory arrays is reduced by a partial activation of array blocks during the active mode and by a charge recycle during the refresh mode. A very-low-power reference-voltage generator is also reported to control the internal chip voltage precisely. These techniques will open the way to using giga-scale LSIs in battery-operated portable equipment.