Author Archives: mathscinotes

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 →

Posted in Electronics | Comments Off on Current Source Built with a Negative Resistance

Engineering as a Social Activity

Posted on 13-March-2011 by mathscinotes

I haven't been able to blog the past week because I have been in Los Angeles at the Optical Fiber Communication Conference and Exposition (OFC). I always enjoy going to this conference. After thinking about it, I enjoy it because … Continue reading →

Posted in Management | Comments Off on Engineering as a Social Activity

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

Daily Loss of Solar Mass

Posted on 3-March-2011 by mathscinotes

Introduction I occasionally work with customers on using solar power to drive some of their remote optical interfaces. These remote interfaces are used to monitor things like pipelines. In one case, it was used to provide Internet service to a … Continue reading →

Posted in Astronomy | 2 Comments

Magic Number Analysis - "Money Factor" in Auto Leasing

Posted on 2-March-2011 by mathscinotes

Introduction One of my sons is a newly minted accountant. He dreams of someday managing a hedge fund. We spend hours talking about modeling data and making predictions. These discussions have convinced me that I need to know more about … Continue reading →

Posted in Financial | 12 Comments

Projectile Time of Flight/Distance Versus Velocity

Posted on 26-February-2011 by mathscinotes

Introduction As I mentioned before, I am reading the book "Modern Practical Ballistics" by Pejsa and am finding some interesting material there. I previously duplicated Peja's derivation for a function describing a G7 standard projectile's velocity versus range. This post … Continue reading →

Posted in Ballistics | 5 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 →

Posted in Electronics | 3 Comments

Calculating the Density of a Planet

Posted on 13-February-2011 by mathscinotes

Quote of the Day Democracy is the theory that the common people know what they want, and deserve to get it good and hard. — H. L. Mencken Introduction I have been reading some interviews with Michel Brown, an astronomer … Continue reading →

Posted in Astronomy | 1 Comment

Neat Use of Gravity Measurements

Posted on 12-February-2011 by mathscinotes

Quote of the Day Your time is limited, so don't waste it living someone else's life. — Steve Jobs One of my sons is into archeology. Whenever he talks about it, I always find the discussion interesting. We were talking … 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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