Category Archives: Electronics

Measuring Power with A Logarithmic Amplifier

Posted on 29-April-2011 by mathscinotes

One of our young engineers asked me why all of us old-timers like to use logarithmic amplifiers when we need to measure input signal power. The answer is simple -- power expressed in dB is a linear function of the … Continue reading →

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Learning How Electronic Parts Work

Posted on 28-April-2011 by mathscinotes

Introduction A few years ago, I gave a lunch time talk on Mathcad to my hardware engineers. During the talk, one of the engineers mentioned that he starts a Mathcad worksheet when he is reading a part datasheet. While he … Continue reading →

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Battery State of Charge

Posted on 28-March-2011 by mathscinotes

Introduction Nearly all of our products are sold with an Uninterruptable Power Supply (UPS) because customers need phone service for emergency voice calls, which we refer to as "lifeline service". Batteries are used for energy storage in all of our … Continue reading →

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Current Source Built with a Negative Resistance

Posted on 13-March-2011 by mathscinotes

Introduction I have seen quite a few schematics lately that are using an operational amplifier (opamp) configured as a negative resistor. I thought it would be interesting to analyze this circuit and show how it can provide an economical solution … Continue reading →

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Will Do Math For Free Lunch

Posted on 3-March-2011 by mathscinotes

Introduction Engineers and managers at manufacturing companies frequently have sales folks come by who want to take you out for a "free" lunch. There is no such thing as a free lunch. They want to sell you something. Except the … Continue reading →

Posted in Electronics | 3 Comments

Drive-By Math

Posted on 15-February-2011 by mathscinotes

Occasionally I have an engineer come by my cube and unexpectedly present me with an opportunity to do math. A few years ago one of the engineers stopped by with a VERY common type of electrical engineering problem. He had an LVPECL logic device that needed to connect to a CML logic device. Of course, these two logic families have different voltage levels and cannot communicate with one another unless some sort of voltage-level shifting (Figure 1) is performed between the devices. We had been using a level-shifting circuit recommended by an IC vendor, but that circuit had turned out to have some problems (I do not know what these problems were). The engineer posing the question had spent a few hours grinding through the math manually and eventually decided that it was too painful to continue. He knew that I use computer algebra systems like Mathematica and Mathcad, so he asked if I could help. Using Mathcad, the following analysis was performed and we had a solution within five minutes. It was quite a demonstration of the power of modern computer algebra systems. Continue reading →

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An Analog Circuit Design Review

Posted on 12-February-2011 by mathscinotes

Quote of the Day The gods do not deduct from a man's allotted span the hours spent in fishing. — Babylonian Proverb Introduction When an electrical engineer asks me what my specialty is, I always respond that I am an … Continue reading →

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"Dying Gasp" from a Circuit Standpoint

Posted on 2-February-2011 by mathscinotes

Introduction The Metro Ethernet Forum (MEF) specifies requirements for carrier-grade Ethernet services. One the features they define is the "dying gasp". A dying gasp is defined as follows: Dying Gasp is a message (or signal) sent by the Customer Premises … Continue reading →

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Pope Gregory XIII and Dual Modulus Counters

Posted on 10-January-2011 by mathscinotes

I discussed a recent dual-modulus counter design in a previous post. I had not thought much about the history of these counters, but I noticed that our calendar is really a dual-modulus counter. Pope Gregory XIII (Figure 1) established the Gregorian calendar (1582) to resolve issues with the Julian calendar. The reason that calendar development is complicated is because a solar year is 365.24219879 days long, which is not easily expressed in terms of simple integer ratios. Ideally, a calendar system is chosen that is simple and that has a mean year length exactly equal to that of a solar year. While not ideal, the Gregorian calendar provides a simple and fairly accurate approximation to a solar year through the use of a dual-modulus counter design based on years with durations of 365 and 366 days. Continue reading →

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Dual Modulus Counter Design Example

Posted on 29-December-2010 by mathscinotes

Quote of the Day I have long been of the opinion that if work were such a splendid thing the rich would have kept more of it for themselves. — Bruce Grocott, British politician Introduction One of the more common … Continue reading →

Posted in Electronics | Tagged | 4 Comments