Designing Ideas

Do analog engineers have more fun than their digital cohorts? I think so, and at the risk of touching off an argument, I offer the following Design Ideas that make good candidates for what I consider an analogger's idea of "fun."

For starters, obtaining gain—lots of gain— poses some amusing challenges. Author Jerome E. Johnston of Cirrus Logic shows how a "Chopper-stabilized amplifier cascade yields 160 to 10,240 programmable gain." The chopper-stabilized front end does the gain selection, while a fixed-gain instrumentation amplifier does the heavy lifting at a fixed gain of 160. This amplifier delivers its gain on DC's doorstep with creditably low noise.

Continuing in our exploration of the low-frequency/high-gain region, Dave Wuchinic of Modal Mechanics explains how a "Current-mode instrumentation amplifier enhances piezoelectric accelerometer." A piezo accelerometer bears a striking resemblance to a ceramic capacitor, so don't overlook the possibility that with this amplifier, you could put that shoebox full of leftover vintage disk-ceramic "toilet lid" capacitors to work as sensors of some sort.

In the great analog sandbox, RF guys have the most fun of all. Nowadays, most of the action takes place in the lower microwave spectrum as wireless devices proliferate and begin to interfere with each other. "Low-cost RF sniffer finds 2.4-GHz sources" can provide an estimate of what's radiating in your immediate area. Vladimir Dvorkin of Linear Technology presents the basics—an antenna, bandpass filter and an LT5534 general-purpose RF power detector IC. You can breadboard the circuit, or modify an LT5534 demo board to do the job.

Contributor Jim McLucas needed a sine wave, but his function generator's frequency span reached only halfway to the required frequency. His solution, "Triangle waves drive simple frequency doubler," shows what a good analogger can do with a thimbleful of discrete components, a couple of toroidal cores, and a few feet of magnet wire. Run a triangle wave through a full-wave rectifier, and you get another triangle wave of twice the frequency. Follow with a low-pass filter to get your sine wave, and Bob's your uncle.

While we're on the subject of having fun (was holiday shopping ever "fun"?), if you're looking for holiday gifts for another engineer, check out Gifts For Engineers, where you'll find assorted everyday objects made from circuit boards, professionally themed neckties, and other oddments. I have never purchased anything from the site, and the usual disclaimers apply.

The best gift you can give—your time and talent—can mean more than material objects. Spend a little time with a youngster: together, you can dismantle an old PC or a TV receiver, build a simple radio receiver, or visit a science museum (don't forget to stop for pizza or ice cream on your way home). Offer your services at a local computer-recycling service or nonprofit computer-education center, become an emergency communications volunteer for the local Red Cross chapter or amateur radio emergency-service group, or donate a box of books to a veterans' hospital or senior-citizens' center. We may make a living designing and selling tricked-out electronics, but we make our lives by helping others.

Best wishes for the holidays, and 73,

—Brad