A Note From the Editor

Welcome to the June issue of Analog Dialogue.

While I was reading an article about a white noise generator in this month’s issue, I remembered my time spent in the DSP group here at Analog Devices. As we knew at that time, everything could be programmed digitally, including speech processing, audio, radar, and medical image enhancement applications. The only limits to this are the clock speed or MIPs and flops of the DSP. The actual processors were from the Blackfin® and the SHARC® families. I remember the breakthrough in understanding the math in the frequency domain vs. the time domain. How easy the math was after an FFT was performed when compared to the long formulas in the time domain. And not to underestimate the programming enhancements that the digital revolution is bringing, but, quite often a simple analog solution using an op amp can do the job much easier. This month’s articles provide some examples.

Do you need a signal with all frequencies present at the same moment in time? A frequency spectrum with no missing frequency? Yes? Well, you could sweep all frequencies with DDS (direct digital synthesis) by using a processor and a DAC or DDS chip and building a programmable frequency generator. But do you really need all frequencies, all the time?

Why not use a white noise generator with an op amp to do this job. A white noise generator produces all frequencies at the same time. No sweeping, no time to wait until a single frequency settles. Aaron Schultz and Peter Haak introduce you, in this month’s RAQ, to a simple op amp circuit that could make your test life a bit easier when you have a DUT. Aaron and Peter are experienced application engineers specializing in instrumentation and precision technology.

Rob Reeder’s article, “High Speed Amplifier Testing Involves Enough Math to Make Your Balun Spin,” adds some humor to our lineup. The article is about high speed amplifier testing. Certainly math is involved, but why does a balun spin? Rob Reeder explains how much phase imbalance of a balun you could tolerate while testing devices (DUT). In the ideal world everything would be easy as everything is matched perfectly. Rob is a senior staff engineer in the high speed area. He has written multiple articles on this topic.

Our third article this month also has something to do with high speed. When you need a very fast flashlight for your high speed camera inspection system, you know how hard it can be to create that very high current in a very short time (microsecond), and over a long period. Creating short and square LED flash waveforms separated by long periods (100 ms to 1 s) of time is not trivial. The challenges with high speed PWM LED drivers are handling the long off-times and short high current times without degrading the square-type waveform needed for proper high speed image processing. Keith Szolusha and Kyle Lawrence, who have written many articles for power applications, explain this in detail. In my experience, if you need even more current, just connect two or more controllers parallel to each other (I always thought in this case one controller acts as a source and the other as a sink—as a result they might oscillate. Our Power by LinearTM group has solved this—and I learned something new.

Sanket Sapre’s article also relates to industrial automation. You know that an IGBT/MOSFET is a voltage controlled device that is used as a switching element in power supply circuits and motor drives amongst other systems. The gate is the electrically isolated control terminal for each device. The other terminals of a MOSFET are source and drain, and for an IGBT they are called collector and emitter. So how do you now drive an MOSFET/IGBT? This article explains the basics and provides details about isolated gate driving. Timing, transition, turn on/off, current, and isolation are the topics Sanket covers in his article. Sanket is an application engineer in the automation group, working mainly with iCoupler® technology.

In this month’s StudentZone, we take a look at phase. We see the term a lot in our field. Out of phase, phase noise, phase locked loop, phase imbalance (see the first article) jump to my mind, but what is phase and how do you measure it? This article in the ADALM1000 series introduces you to phase and hopefully answers those questions.

Do you have the ADALM1000 out on your table? OK, let’s get a bit more familiar with the inductors. As before, Doug Mercer and Antoniu Miclaus are your instructors and will guide you through the exercises.

And as we have for 51 years, we invite you to be part of the “dialogue” in Analog Dialogue. You can get in touch through our blogFacebook page, or email. Let us know how we’re doing and what you’d like to see from us in the coming months.