A Note From the Editor

Welcome to the December issue of Analog Dialogue.

My recent visit to Boston, Massachusetts brought me to the Museum of Science (mos.org). A wonderful place for everybody to be, especially if the weather is not as good as expected. There are a lot of activities based around science of course, which makes an engineer’s heart leap. 

One live presentation, “Bottling a Plastic Problem,” was all about microplastics—where they go, what they do, and what we can do to stem the rising tide of these tiny, pervasive pieces.

Microplastic is everywhere—in beer, water, our air, and in our food chain. Scientists have even found microplastics in mosquitos. It’s a very concerning development, as we do not understand the full impact of plastics on our health. There are some initiatives to eliminate plastic and to replace it with more harmless alternatives.

There are also efforts to remove the plastic already in the environment. For example theoceancleanup.com, which uses nature, science, and technology to assist in this massive endeavor. Who knows, maybe this will become a future exhibit at the Museum of Science one day.

I can only encourage you to think twice when you get plastic bags at markets, or use plastic coffee cup lids, forks, knives, spoons, and straws during meals.

In addition to my metal coffee cup, I am planning to buy my own metal forks, knives, and spoons for my next visit to Boston.

And now, onto the featured technologies in this month’s Analog Dialogue.

Data acquisition systems are used in many industries for a wide range of applications, such as research, analysis, design verification, manufacturing, and test. By nature, these systems interface with various sensors, which poses a challenge to the front end. Different sensor sensitivities must be considered—for example, a system may need to interface to a load sensor that has a maximum output of 10 mV and sub-microvolt sensitivity, while also interfacing to a sensor that is preconditioned for a 10 V output. Programmable gain instrumentation amplifiers (PGIAs) are a good solution for the front end. They can accommodate the sensitivities of the various sensor interfaces, while optimizing signal-to-noise ratio. This article discusses the various integrated PGIAs in the ADI portfolio and the advantages of using them—such as for best CMRR, low offsets, and exceptional gain and drift performance. In general, it is always preferable to use integrated PGIAs because of these inherent advantages. Our author is Kristina Fortunado, who joined ADI in 2009 and is working as a product applications engineer for the Linear Products and Solutions Group. She graduated from De La Salle University with a bachelor’s degree in electronics and communications engineering. 

Instrumentation amplifiers are the workhorse of sensing applications. Our author, Hooman Hashemi, explores some ways to take advantage of the amplifiers’ balance and excellent dc/low frequency common-mode rejection (CMR). These amplifiers can be used with resistive transducers (for example, strain gage) when the sensor is physically separated from the amplifier. Hooman also presents methods to increase the noise immunity of such gain stages while making them less sensitive to supply variation and component drift. Measured performance values and results will also be presented to show the accuracy range to allow a quick evaluation for end-user applications. Hooman joined Analog Devices in March 2018. He works on characterizing new products and developing applications that showcase product features and uses. Hooman graduated from the University of Santa Clara and San Jose State University.

Industrial, automotive, and networking companies use the full array of the available topologies of the dc-to-dc converters, employing buck, boost, and SEPIC in different variations. In an ideal world these firms would use a specialized controller for each new project. However, adapting each new chip requires significant investment due to the costly process of compliance testing to meet automotive standards, and verification functionality for the specific applications and conditions. The obvious solution of reducing development cost is employing already approved and verified controllers for multiple topologies. The LTC3892 is a versatile controller, which is already widely used in automotive and industrial applications. This article explains how to use this buck controller to generate negative voltages and positive outputs immune to input voltage drops and spikes. Our author is Victor Khasiev, a senior applications engineer at ADI with extensive experience in power electronics both in ac-to-dc and dc-to-dc conversion. He has written multiple articles and holds two patents for efficient power factor correction solutions and advanced gate drivers. Victor enjoys answering questions about ADI products, the design and verification power supply schematics, the layout of printed circuit boards, troubleshooting, and participating in testing final systems.

Can you measure a difference signal with an instrumentation amplifier? It’s the question for our monthly RAQ. In many lighting applications, measuring the relative intensity of two light sources is more important than measuring their individual intensity. For example, it is very helpful to compare the brightness inside a control room to any other room in the same building so that adjustments can be made any time of day. One way to determine the relative intensity is to measure the different outputs of two additional light detectors, one in the control room and one in the other room. The difference will be converted to a single-ended voltage signal with a ground reference. Chau Tran explains all this for you. Chau joined Analog Devices in 1984 and works in the Linear and Precision Technology Group in Wilmington, MA. In 1990, he graduated with an M.S.E.E. degree from Tufts University. Chau holds more than 10 patents and has authored more than 10 technical articles.

In this month’s StudentZone, we take a look at band-pass filters. We have already discussed the main filter components of inductors, capacitors, and resistors in previous StudentZone articles. A band-pass filter is the next logical function you should be aware of. I am happy that Antoniu Miclaus and Doug Mercer continue to inform and teach with their StudentZone series. 

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.