K. Schumacher

Analog CMOS realization of fuzzy logic membership functions

The design of a monolithic CMOS analog function synthesizer based on a current-mode algorithm and its application in fuzzy membership function synthesis is presented. The proposed circuits require only one reference current, independently of the course or the number of implemented functions. The networks are temperature and technology insensitive. Other features are a small chip area and a simple design process for any arbitrary functions. Matching considerations allow a prediction of the available approximation accuracy. Theoretical evaluations are validated by measurements of several membership functions fabricated in an experimental 1.0- mu m CMOS technology. >

Universal low cost controller for electric motors with programmable characteristic curves

The realization of a universal low-cost controller for electric motors in CMOS technology with programmable characteristic curves is presented. With regard to the required chip area of 2.7 mm/sup 2/ in a 1.6 /spl mu/m, 40 nm technology, the general advantage in comparison to microcontroller-based solutions lies in the low factory costs. The analog dc power supply is generated directly from the 230 V ac power line. An on-chip functional unit controls the firing current for the off-chip motor driving triac. Features of this functional unit are torque control and overload protection, firing, and post firing control. A new method was used to implement programmable multidimensional characteristic curves which are temperature and technology insensitive. In the actual controller application for a drilling machine motor, the mask-programmed curve shapes have been generated with the help of fuzzy algorithms. An impression of the reproducibility of multidimensional characteristic curves in manufacturing, as well as the accuracy of their precalculation, is given by introducing simulated and measured statistics of the actual design.

Mismatch Modeling and Simulation—A Comprehensive Approach

This article describes a comprehensive approach to mismatch simulation and modeling as needed for integrated circuit design. Local device mismatch as well as global process variations and parameter correlations are regarded. A method for mismatch modeling based on spatial frequencies is described, which enables to overcome insufficiencies of the first order models. Measurement results are presented to demonstrate the achieved modeling precision. All models and methods mentioned here are commercially available in the simulation tool GAME (General Analysis of Mismatch Effects) which is used in the semiconductor industry since 1998.

A linear operational transconductance amplifier with automatic offset cancellation and transconductance calibration

Operational Transconductance Amplifiers (OTAs) with linear input-output characteristics have become the focus of attention as a fundamental building block for analogue time-continuous circuits. Especially they are used in filters and instrumentation amplifiers with high cutoff- or corner frequencies. This paper describes a simple CMOS circuit technique for realizing a precision linear amplifier using the square-law function of MOS transistors. The linear input-output characteristic is not influenced by the MOS threshold voltage dependence on the source-bulk voltage or other effects. To eliminate the remaining imperfections the new proposed technique combines analogue time-continuous and time-discrete circuitry. By the use of two adjustment phases, the offset can be suppressed effectively and the transconductance can be put back or newly defined in a given range. In a third phase the OTA works along with further time-continuous circuits. The proposed circuitry can be implemented with a double or a single-ended output stage. Due to symmetrical internal signal paths, the best results in terms of linearity, PSRR and CMRR are obtained in combination with a double-ended output stage.

Overcoming insufficiencies of first order mismatch modeling

Whereas the mismatch law of area [1] and law of distance [2] are acceptable in a first order sense, there a several measurement results which show significant deviations from these simple models. This paper describes a more sophisticated approach to mismatch modeling, based on spatial frequencies on the wafer. This makes it possible to overcome the insufficiencies of the first order modeling and to achieve a generalized representation of mismatch effects. A method for determining the spatial spectrum from measurement data is presented.

Mismatch effects explained by the spectral model [MOS devices]

The currently available first order mismatch models cannot explain many of the observed effects. The physical modelling approach of the spectral model described in this paper gives a very precise description of actual mismatch behaviour in a closed form and leads to a deeper understanding. Together with small geometry considerations a very good prediction of mismatch effects for a wide range of layout structures can be obtained, which are verified by measurements.

Accuracy Optimization of Analog Fuzzy Circuitry in Network Analysis Environment

In contrast to digital circuits the performance of analog integrated circuits and therewith of analog fuzzy components highly depends on local matching accuracy. Especially for scaled structures down to the submicrometer range the local statistical mismatch effects increase rapidly. As in network analysis programs like SPICE [1] local statistical mismatch effects are not represented within the implemented device modelling, in consequence no analysis options are available to compute their influence on electrical circuit characteristics in fabrication. Fast analysis methods have been developed and implemented [2] into SPICE and the compatible simulator BONSAI [3], using especially mismatch modelling for MOS transistors introduced in [4] and [5]. Simulation methods and simulated yield statistics in comparison to measurements of fabricated analog fuzzy applications are reported.

Analog CMOS-Realization of Fuzzy Logic Membership Functions

A new network structure to realize any fuzzy membership function working in current-mode is presented. Only one reference current is required independent of the course or the number of the implemented functions. The networks are temperature insensitive and only a small chip area is needed. The design procedure is very simple and fast due to the regular circuit structure. Theoretical evaluations are validated by several membership functions fabricated in a 1.0 ¿m CMOS-technology.

Local matching properties of switching elements and their influence on the accuracy of switched differential current mirrors

A switched differential current mirror with an offset cancellation technique is presented. Because of its symmetrical signal paths, the charge injection in nominal is minimized. By the means of statistical simulation, the error caused by local parametric variations between the switching elements has been estimated. Methods making the current mirror more robust against local mismatching of the switches are proposed. Statistical simulations are presented and discussed.

Yield: High Performance Analog Circuit Design With Regard To Statistical Aspects

A novel approach to the computer supported design of high performance analog circuits is presented. Circuit design and dimensioning is effectuated utilizing procedural descriptions of the designers own techniques and given libraries, according to designer-given specifications. Thus the designer is enabled to concentrate on an increased number of inter-dependences between the circuits properties and specifications than would be possible using manual calculation or fully automatic design systems. Free programmability and an open model interface give flexibility as well as improved design accuracy and novel means of analysis. Taking into account noise and statistical local and global matching calculations the designer can incorporate yield aspects into the design flow. The usage of the YIELD design tool is demonstrated by dimensioning a patented temperature compensated, resistorless, precision current reference with regard to local matching.