Design Article
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pcsalex
we used to learn mathematics - even diff equations - in our high ...
p_sheinkin
You are right about elemental principles of physics that must be taught before ...
Development of a Spice op-amp macro-model for current-feedback amplifiers (Part 1 of 2)
Jian Wang and Tamara Schmitz, Intersil Corp.
8/1/2010 10:46 PM EDT
Current-feedback amplifiers (CFAs) are the high-speed relatives of more common voltage-feedback amplifiers (VFAs). CFAs have wider bandwidths and faster slew rates. Applications like DSL rely on their fast and strong output drives. Models are important because they allow engineers to test designs before they go through the time-intensive and costly process of building a working prototype.
In this article, we introduce you to a circuit model for a current-feedback amplifier. Since it would take far too long to simulate every nuance of a complete design, this macromodel simulates the most common effects such as transient response, frequency response, voltage noise and output slew rate limiting. Detailed descriptions of each stage in the model will be presented with examples of model performance and correlation to actual device behavior.
The article is presented in two parts, as pdf files (no registration required), as follows:
· Part 1 discusses the overall approach, the input stage, gain stage, frequency-shaping stages, noise module, and output stage, click here.
· Part 2 discusses the simulation results and includes a net list; it will be posted on August 5, 2010.
About the authors
Jian Wang was born in China in 1975 and has served as an applications engineer with Intersil since 2005, focusing on high speed amplifiers and drivers. He received a Ph.D. from the University of California at Davis in 2006.
Tamara Schmitz holds BS, MS, and PhD degrees in electrical engineering. She taught analog circuits and test development engineering as an assistant professor at San Jose State University. With eight years of part-time experience in applications engineering, she joined Intersil in August 2007 as a principal applications engineer.
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Rich Krajewski
8/2/2010 5:16 PM EDT
Honest to goodness, they should introduce SPICE to students at the high school level. It's not that hard. Hmmm, maybe SPICE isn't that hard, but getting public schools to push the envelope is.
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kendallcp
8/3/2010 12:04 PM EDT
That's the tip of the iceberg. High schools, or their equivalents around the world, should offer a foundation signals and electronics course for any students considering a career in engineering. I fear that SPICE is in fact so easy that if you teach it too early, you'll not then be able to teach people how it works, and how you get an understanding of a circuit from its deeper principles.
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goafrit
8/3/2010 11:17 PM EDT
SPICE's problem is that it is not graphic enough. But I think to high school may be a problem. The problem with SPICE is not SPICE, rather what SPICE does. Can you enjoy SPICE if you are clueless about what a transistor is? No, so, we need to teach and extend that concept down the educational line. SPICE is a tool and emphasis must not be built on it. Let us focus on the core which is the component: transistor, capacitors, diodes, resistors, etc
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p_sheinkin
8/4/2010 5:13 AM EDT
You are right about elemental principles of physics that must be taught before teaching SPICE.
As "old model" engineer from french university I only can agree with your view...
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pcsalex
8/4/2010 3:53 PM EDT
we used to learn mathematics - even diff equations - in our high school[=gymnasium],where we learned also Physics,Chemistry and Biology instead of "science", but people from that schools are Theodor von Karman, Edward Teller, Andy Grove and many more.
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