Category Archives: Electronics

My first blog post discussed the following interview question I received many years ago. You are handed a 1 F capacitor charged to 10 V and two boxes containing uncharged capacitors: one box contains an uncharged 1 F capacitor and … Continue reading →

A common electrical engineering task during the design of a circuit card is designing a way for the circuit to measure its own temperature. Knowing the temperature of a circuit board is important for compensating for component temperature variations and diagnosing heat problems. Normally, I use a thermistor as my temperature probe. A thermistor is a resistor whose resistance varies with temperature (Figure 1). The thermistors that I use have a negative temperature coefficient (NTC), which means their resistance reduces as their temperature increases. In many ways, thermistors are a great sensor: cheap, tough, small, and accurate. Continue reading →

I just saw the announcement that Bob Pease died in a car accident after leaving a memorial to Jim Williams, another analog legend. This is very sad. I have read everything that Bob Pease wrote. His column for Electronic Design, "Pease Porridge," was required reading for my crowd. Continue reading →

Analog engineers often have to design filters, which generally entails a lot of polynomial manipulation. Since I am currently designing some active filters, I thought it would be worthwhile documenting a filter function that I am using right now, but that is not widely known. This is the Papoulis or Optimum "L" filter. For this article, I will refer to this filter as the "L-filter." The "L" stands for Legendre, a mathematician whose like named polynomials are used in the derivation of the function. Continue reading →

I just saw the announcement that Jim Williams passed away. This guy was an inspiration to me. His apps work at National Semiconductor was a model for the industry. His articles in magazines like EDN provided real-world examples of elegant analog design techniques. His books, particularly Analog Circuit Design: Art, Science and Personalities, provided wonderful examples of problem solving. He will be missed. Continue reading →

During a recent circuit design review, I saw the need for a simple two-pole filter in one region of the circuit. As I thought about, this filter might be a good example to work through here in the blog. While the application is rather routine, it does illustrate the general process involved in designing one of the most common forms of a low-pass filter. Continue reading →

Introduction I regularly get questions on using solar panels to power our Fiber-To-The-Home gear (FTTH). You might think that sounds kind of odd, but it makes a lot of sense for many businesses and municipalities. For example, every municipality has … Continue reading →

As you guys know, I've been on a mission to learn how electronic parts work. As an engineer, I have a decent knowledge of certain parts of electronics but I always want to know more. What makes the leviton switches … Continue reading →

Introduction An engineer came by my cube and asked me a question about a part we use in one of our older designs. This clever little device is made by Maxim and is called the 3660. This chip is used … Continue reading →