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Online tool for active filter design

Intersil’s iSim Active Filter Designer is an online tool that assists with the design of operational amplifier-based active filters and minimises design differences in the transition from simulation to production. Among the claims that Intersil makes for it are that it yields an optimised set of component recommendations, including a ranked list of possible amplifiers that fit specific requirements, taking into account supply voltages, signal-swing limits, and dynamic characteristics that more basic tools may overlook. iSim’s component calculations, its authors say, also take account of subtle amplifier and parasitic-component effects, improving the nominal filter accuracy and increasing design margins. The opamp macromodels in the tool include second-order effects such as bandwidth vs gain and loading, I/O impedance, and I/O clipping. These predict physical limitations online before committing to production: designers get the ability to view the inter-stage and final output, AC response, noise, and step response, making it possible to see what is going on inside a multi-stage filter design and assess the impact of choosing alternate devices.

Based on an initial parts selection from Intersil’s range, the user can perform multiple simulations of a design online or locally using a personal computer to explore the effects of substituting different components. Designers can also download results to Intersil’s iSim PE (Personal Edition) tool for further analysis using a more general Spice simulator platform.

The iSim tool evaluates lowpass fi lter designs from second through sixth order, and the company is expanding it to include high- and bandpass options; it can work with products ranging from the micropower ISL28194 op amp (1.65 mW), to the highestspeed current feedback op amp, the EL5167 (over 600 MHz using less than 100 mW power). The product provides solutions ranging from 5 Hz to 50 MHz for products requiring power rails of 1.8 to 40V.

Intersil, www.intersil.com/iSim/ActiveFilterDesignToolOverview.pdf.