Correlation between EMI-induced failures and large-signal response of fet-input opamps

Correlation between EMI susceptibility of opamp circuits and asymmetry in the slew-rates of the basic opamp is discussed with reference to FET-input devices. For the LF355 opamp the role played by an internal feedback loop on the common-mode, slew-rate and susceptibility performances is analysed. Other FET-input opamps, such as the OP42, which exhibit an almost symmetric slew-rate, have a very small EMI susceptibility.     

The role of a bidirectional cavopulmonary anastomosis in the correction and palliation of complex congenital cardiopathies

Between May 1990 and January 1998, 68 patients underwent bidirectional cavo-pulmonary anastomosis. We evaluated all patients in whom the bidirectional cavo-pulmonary anastomosis was associated with additional pulmonary flow (group A) and those in whom it was associated with biventricular repair (group B). Group A included 23 patients (33.8%), 14 males and 9 females, mean age 25 years and 6 months (range 4 months-16 years). Diagnoses were double outlet right ventricle (6), univentricular heart (6), tricuspid atresia (5), congenitally-corrected transposition of the great arteries with ventricular septal defect and pulmonary stenosis (3), right isomerism (2) and pulmonary atresia with atrioventricular canal (1). Group B included 13 patients (19.1%), 6 males and 7 females, mean age 13 years and 7 months (range 1 year-37 years). Diagnoses were pulmonary atresia with intact ventricular septum (4), Ebstein's anomaly (3), tetralogy of Fallot (3), atrioventricular canal (1), hypoplastic right ventricle (1), and pulmonary and tricuspid insufficiency (1). Four patients (17.3%) in group A died in the postoperative period, whereas there was no postoperative mortality in group B. Follow-up data were available in 31 patients (19 from group A, 13 from group B). Mean follow-up was 1 year and 6 months (range 30 days to 6 years). Evaluation was done by NYHA class functional status. In group A, 14 patients are doing well (NYHA I or II), while five patients (26.3%) underwent Fontan operation with one death. All group B patients are currently doing well (NYHA class I or II). In group A, complications were pericardial effusion (7), transient superior vena cava syndrome (5), pleural effusion (4), chylothorax (1) and rhythm disturbance (1). Complications in group B involved neurological events (2), pleural effusion (1) and rhythm disturbance (1). Bidirectional cavo-pulmonary anastomosis can be associated with additional pulmonary flow with good short- and intermediate-term outcome. Concern remains for the ability to properly regulate the amount of effective pulmonary blood flow. Bidirectional cavo-pulmonary anastomosis can be associated with biventricular repair in patients with diminutive right ventricles, amenable to anatomic complete correction, with good clinical outcome.     

New macromodels and measurements for the analysis of EMI effects in741 op-amp circuits

Presents the design of two macromodels for the 741 op-amp that prove trustworthy in simulating the consequences of high-frequency, large-amplitude sinusoidal voltages that represent EMI (electromagnetic interference) effects and are applied to the input of inverting and noninverting amplifiers. One of the macromodels accounts for power supply voltage change, reproduces correct voltage waveforms at the main nodes of the full circuit, and gives rise to computer time saving factors of 5 or more in comparison with full device-level simulations. The other comprises the minimum number of components necessary to estimate the DC output voltage only and reduces the simulation time by a further factor of about 5. Extensive experimental results were obtained from laboratory measurements and are compared with the numerical simulations     

High speed, high capacity ATM optical switches for futuretelecommunication transport networks

This paper describes the work carried out in the RACE Project R2039 ATMOS (asynchronous transfer mode optical switching). The project is briefly illustrated, together with its main goal: to develop and assess concepts and technology suitable for optical fast packet switching. The project's technical approach consisted in the exploitation of the space and wavelength domains for fast routing and buffering: The major achievements are then reported. Four different switch architecture concepts have been proposed, investigated and developed, all based on a high speed optical routing matrix electrically controlled at lower speed. The basic optical key components and subsystems (wavelength converters, space switches and optical buffers) are described in detail, with the outstanding results obtained and the corresponding projected performance. In particular, system demonstration of wavelength conversion at 10 and 20 Gb/s has been realized, to show the usefulness of the ATMOS technology both to implement optimized high performance optical packet-switching fabrics as well as transparent optical circuit-routing nodes. Four rack-mounted, reduced size demonstrators of basic switching matrices have been designed and implemented scalable to real system sizes. The obtained good results in terms of bit error rate and hardware integration are reported, showing that ATM switches are feasible with state of-the-art optical technology     

Reflectance measurements on second-surface solar mirrors using commercial spectrophotometer accessories

Commercial spectrophotometers can be used with suitable accessories (specular reflectance accessories, integrating spheres) to perform accurate measurements on second-surface reflecting mirrors normally used for solar collectors. In this article the results obtained with different spectrophotometers and accessories are reported and discussed. Good convergence of the measurements was obtained with particular expediency in the visible range. In the case of specular reflectance accessories, a correction of the results is necessary account for the lateral shears of the second surface reflected beams. When using an integrating sphere as an accessory, its reflectance port must be sufficiently large in order to capture the most significant reflected beams. In the near infrared range, acceptable values can be obtained only for good alignments of the specular reflectance accessories and for internal coatings of the integrating spheres with a high diffuse reflectance in the entire solar range.