Monday, August 07, 2006

Editors' Notes—Volume 40, Number 2, 2006

As faithful readers already know (and are perhaps weary of knowing!), Analog Dialogue is celebrating our 40th anniversary in print. But there is another significant anniversary to celebrate: Exactly 20 years ago, in Volume 20, No. 2 (1986), we broke with our purely analog past and introduced the first Analog Devices digital signal processor (DSP), the ADSP-2100. You may be interested in recalling the theme of the Editor’s Note welcoming our readers to that issue:

“Microprocessor?” we hear you ask. “Isn’t it a bit unseemly for a nice ‘Analog’ IC company to be designing a microprocessor? (What could be more digital?)”

Good question.

Our objective has always been to design and manufacture cost-effective components that are key elements of the signal path for processing real-world (i.e., analog) data and for which performance is maximized and errors minimized.

The signal path? Real-world data almost always starts out as analog (i.e., parallel, nonnumeric) variables, which are measured by sensors that provide analog electrical signals—voltage and current. The signals must be accurately and speedily amplified, conditioned (almost always in parallel), and converted to digital for processing. Once in digital form, they must be processed rapidly. Often, they again wind up as analog signals.

Key elements of the signal path include preamplifiers, analog signal processors, data converters to and from digital, and—when the signal is in digital form—a digital processor. Inadequacy in any one of the key elements—amplifier, analog processor, data converter, or microprocessor—can cause poor performance of the overall system.

Obstacles in the signal path include noise, drift, nonlinearity, and measurement lag at the analog stages, similar obstacles in conversion—and throughput delays in digital processing, often because of the lack of parallelism in von Neumann architecture.

Throughout our history, our role in the signal path has been to initiate new products (or product lines) when dissatisfied with the cost-effectiveness of what’s available (which is often limited to user-assembled kludges, when nothing else is available). At this point in time, we (and our competitors) have virtually eliminated the user-assembled amplifier, signal conditioner, and data converter by designing and marketing families of cost-effective products.

We have always been dissatisfied with the cost, power dissipation, and slow throughput in the digital domain; this concern led to our pioneering development of CMOS multipliers and other digital signal-processing ICs (note that because we were already familiar with analog multipliers, digital multipliers became just another analog signal-processing tool; note also our commitment to signal processing—not payroll, desktop publishing, or order-handling products). Our dissatisfaction with the complexity of systems using Bit-Slice parts led to the powerful and compact Wordslice™ microcoded system parts.

And finally, our dissatisfaction with insufficient throughput in DSP processors led to design of the ADSP-2100, which stresses the use of that analog characteristic, parallelism, to minimize instruction cycles, whether in processing, data transfer, or interrupt handling. It’s neat! We invite you to read about it.

Dan Sheingold []

Dr. Leif’s World—And Ours

In this issue, enjoy Oscar Stirs, part three of Niku’s quest to understand the start-up phase of an ideal oscillator. In Dr. Leif’s world, the effects of global warming have already been felt, yet there is hope for the future. Is our outlook as bright, or will some of the cataclysmic events experienced in Niku’s lifetime become reality in ours? Everyone should see the intentionally biased movie, An Inconvenient Truth, regardless of their current views on global warming. At the very least it will make them wonder about how robust or fragile our environment is and question what they read in the popular press. Some may be motivated to act by reducing their own impact on our ecosystem or becoming advocates for change. For more information, and some simple suggestions for becoming carbon neutral, visit

VoIP—Pro and Con
After using VoIP for about two years, I finally cut my personal ties with Ma Bell. For less than 20 dollars a month I got everything that was previously provided by my land line, plus a lot more. Some of the cool features include voice mail messages sent via email, allowing me to access them from any PC, and the ability to reject anonymous calls without being forced to jump up and check the caller ID. In addition, I can make unlimited calls to the US and Canada, and limited free international calls. So, what’s the downside? Well, even with 8 Mbps Internet access and 92% quality of service (QoS), the voice quality, noise level, and echo rejection are not as good as with the wired phone. Also, a call is occasionally dropped, something I never experienced with the land line. Furthermore, I’d lose my VoIP connection in the event of a power failure, in contrast to the always-up reliability of the plain old telephone system (POTS). With a cell phone as a backup, though, VoIP is a smart choice. In this issue, read about implementing VoIP on a Blackfin processor.

Power-Supply Management
With today’s portable devices and green appliances, power consumption must be kept to a minimum, yet complex consumer electronics equipment often requires multiple power supplies for the analog circuitry, memory, microprocessors, DSPs, and ASICs. These supplies must be turned on and off in sequence to avoid damage to their associated components, with timeouts occurring in the event of a system fault. All of this increases the importance of integrated power-supply management. In this issue, learn the basics of the problem and of the available solutions.

Class D Amplifiers
Class D amplifiers provide the advantages of higher efficiency, smaller size, and lower cost, while still achieving low distortion, wide dynamic range, and clickless muting. Recently, everyone seems to be writing about Class D. After reading the article in this issue, you may also be interested in reading “How Class D Amplifiers Work” by Jun Honda and Jonathan Adams, “Design and Analysis of a Basic Class D Amplifier” by Chi Ho Li, and “Class D in Audio Hubs Extends Battery Life” by Robert Hatfield. All can be found at

Scott Wayne []


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