1 V CMOS subthreshold log domain PDM

A new CMOS circuit strategy for very low-voltage Pulse-Duration Modulators (PDM) is proposed. Optimization of voltage supply scaling below the sum of threshold voltages is based on Instantaneous Log Companding processing through the MOSFET operating in weak inversion. A 1 V VLSI PDM circuit for very low-voltage audio applications such as Hearing Aids is presented, showing good agreement between simulated and experimental data.Comisión Interministerial de Ciencia y Tecnología TIC97-1159, TIC99-1084European Union 2306

On the Active Compensation of Operational Amplifier Based VCVS

A unified treatment of the active compensation for VCVS realized by operational amplifiers is presented. It is a summary of low-sensitivity circuit structures which can be either magnitude or phase compensated. The performance of such a circuits is discussed in detail. Experimental data for some of them are also included

Novel active-compensated weighted summer

A summer amplifier with extended bandwidth is proposed. Compensation of the frequency characteristics is achieved by employing two operational amplifiers instead of external reactive components

Efficient state reduction methods for PLA-based sequential circuits

Experiences with heuristics for the state reduction of finite-state machines are presented and two new heuristic algorithms described in detail. Results on machines from the literature and from the MCNC benchmark set are shown. The area of the PLA implementation of the combinational component and the design time are used as figures of merit. The comparison of such parameters, when the state reduction step is included in the design process and when it is not, suggests that fast state-reduction heuristics should be implemented within FSM automatic synthesis systems

Efficient realization of a threshold voter for self-purging redundancy

The self-purging technique is not commonly used mainly due to the lack of practical implementations of its key component, the threshold voter. A very efficient implementation of this voter is presented which uses a decomposition technique to substantially reduce the circuit complexity and delay, as compared to alternative implementations.Comisión Interministerial de Ciencia y Tecnología TIC97-064

Chaos in a Switched-Capacitor Circuit

We report chaotic phenomena observed from a simple nonlinear switched-capacitor circuit. The experimentally measured bifurcation tree diagram reveals a period-doubling route to chaos. This circuit is described by a first-order discrete equation which can be transformed into the logistic map whose chaotic dynamics is well known.National Science Foundation ECS-8542885Comisión Interministerial de Ciencia y Tecnología 0245/81Office of Naval Research under Contract NOOO14-76-C-057

Design of RC-active oscillators using composite amplifiers

The design of composite opamp Wien-Bridge oscillators is systematically approached by using a general model including amplitude control issues. Two different design criteria are presented and their main features summarized. A general composite opamp topology from which a catalog of structures can be obtained in a systematic way is presented. Experimental data are included illustrating the performance of the proposed design criteria

A new nonlinear time-domain op-amp macromodel using threshold functions and digitally controlled network elements

A general-purpose nonlinear macromodel for the time-domain simulation of integrated circuit operational amplifiers (op amps), either bipolar or MOS, is presented. Three main differences exist between the macromodel and those previously reported in the literature for the time domain. First, all the op-amp nonlinearities are simulated using threshold elements and digital components, thus making them well suited for a mixed electrical/logical simulator. Secondly, the macromodel exhibits a superior performance in those cases where the op amp is driven by a large signal. Finally, the macromodel is advantageous in terms of CPU time. Several examples are included illustrating all of these advantages. The main application of this macromodel is for the accurate simulation of the analog part of a combined analog/digital integrated circui

New analogue switch circuit having very low forward resistance

A new circuit realisation for an analogue switch is reported. The main feature of the proposed design is the low value of the forward resistance as compared with commercial switches. Experimental data confirming the performance of the circuit are also included