Designing Ideas

Our leadoff Design Idea seeks to settle the eternal question: No, not "boxers or briefs?" but "linear or switched mode?" In "Low-dropout regulator, SMPS cascade suppress ripple, maintain efficiency," Author Scot Lester of Texas Instruments briefly explores advantages and disadvantages of each voltage-regulation method and decides in favor of...both. You use a switched-mode preregulator to efficiently smooth out large input-voltage swings, and then follow up with a linear regulator to minimize switching noise. If you're really worried about noise on your power-supply lines, TI offers an app note that explains how to minimize noise produced by linear regulators.

Batting second, "Novel circuit isolates temperature sensor from its host" by Alfredo Saab and Tamer Mogannam of Maxim Integrated Products, presents an interesting method of transmitting power and intelligence (in this case, the temperature at a remote location) via a single pair of wires. This circuit modulates the power-supply period by clamping a temperature-controlled load across the isolated power supply. In turn, the modulated load current gets sensed at the sending end and delivered as variable-period pulses. Although the specified transformer carries a 500V isolation rating, selecting or designing a higher-voltage equivalent shouldn't prove difficult.

In the on-deck circle, author Sid Levingston of Portland, OR, offers some mathematical background that can help you "Find resistor values for arbitrary programmable-amplifier gains"— not exactly an everyday problem encountered by the analog team, but you may want to file a copy of this Design Idea for future reference. If your recollection of matrix algebra currently bats in the high .200s, this web site's blog offers a refresher.

If broiling in the bleachers and suffering chili-dog-and-beer poisoning isn't your idea of a good time, slide on over to your local air-conditioned bookstore or public library and score a book or three. If you've ever felt vaguely uneasy about the rapid turnover of goods in our consumer-driven society, you no doubt felt doubly uneasy when you consigned your two-year-old PC to the scrap heap. The cover of "Made to Break: Technology and Obsolescence in America" sports an eye-catching photo of a shipping container almost filled with CRT displays, and author Giles Skade includes enough discussion of electronics' role in planned obsolescence to satisfy EE readers. With HDTV looming on the horizon, we'd better get ready for the Big Enchilada of Obsolescence.

Anybody wanna buy my 1950s RCA NTSC color-bar generator? No? Guess I'll toss it. In "Gone Tomorrow: the Hidden Life of Garbage," author Heather Rogers explores the history of garbage past and garbage present— the 4.5 pounds of waste generated every day on average by every American. It's unclear how our society might go about untangling the messy snarl that links planned obsolescence, garbage disposal, and an unquenchable thirst for petroleum and other resources, but maybe we'd better start paying attention.

Or maybe we could leave the planet. All we need is an engine and we're good to go. In "The Hunt for Zero Point: Inside the Classified World of Antigravity Technology," Nick Cook, a defense journalist and aerospace consultant for Jane's Defence Weekly, attempts to follow up optimistic predictions about alternative propulsion methods made in the mid-1950s by such luminaries as Lt.-General Nathan Twining. By the book's end, we're left with tantalizing glimpses of highly unconventional technologies that may have originated in World War II Germany and been recovered as "spoils of war" by U.S. military intelligence.

Normally, I'd dismiss this book as science fiction, but the author's credentials and extensive experience in aviation reporting lend it credibility. Read it, and decide for yourselves whether there's an E-ticket ride in our future.

Until next time, 73

—Brad