Category: Learning

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Analog Electronics Learning Life Politics Supply Chain Work

The Great North

This blog started when I moved back to Cleveland. Really, it was a little bit sooner, but it got going full time once I was settled in back in May. Since I’ve been back, I’ve actually really enjoyed it. There are some things I miss about Austin (where I used to live), but I am happy with my decision, most notably because of my job. I feel like I am part of the minority that is moving back North, that others in my generation are more likely to head south at the first opportunity.

Is there any reason to live in the north anymore?

Let’s go over the sour points first:

  1. It’s cold — No brainer on that one, it definitely snows more in Ohio than in Texas, but you do get the benefit of some winter sports (skiing, tubing, professional snowman making) and the picturesque nature of seeing snow on Christmas or at other times (this wears off after about two weeks). Unfortunately, the cold lasts longer than most people would like in Ohio. Back in Texas I was wearing shorts and tubing down the river by March.
  2. Gas/Heating —  This year might be the best example of expensive heating, but it has yet to play out. Oil prices are falling right now but could easily rise again in time for winter. There are some other (corny) ways to heat your house, so oil prices do not have the final say in how much we’ll be paying per month for oil north of the Mason-Dixon line. On the bright side, we’re paying WAY less for electricity than the south during the summer months.
  3. Young people — There’s kind of an avalanche effect to people migrating out of one city or into another. The more people that move somewhere, the “hotter” the scene becomes and more people want to move there. Cleveland still has a pretty vibrant night life, but it pales in comparison to Austin and some other larger cities.
  4. Urban Development — Suburbs happen. Sprawl happens. The longer a city has been around (such as those  in the north), the more people want to spread out and get their own space. This is slowly happening in the south (Dallas, anyone?), but Austin is still relatively compact. With newer, smaller, growing southern cities, urban planning can help to compact things and make them more accessible. If you are moving to a city in the north, it’s likely that a lot of the urban development is already done (though not completely).
  5. Jobs — We hear about the manufacturing jobs lost in Mid-West every time you turn on NPR. But there are also less large corporations in the north, due to some of the above listed reasons and less amiable tax laws than parts of the south.

But there is a lot of bright spots in Cleveland, even in the winter!

  1. Water — Necessary for life, right? Well some people didn’t really think about that when they were setting up new cities and towns in the southwest (I’d reference all of Arizona first). The Mid-West though? We’ve got tons of it! The great lakes are a great resource, whether for shipping, recreation, fishing or even lighting on fire (go Cleveland!). It definitely makes the summer months that much better and makes the winter months that much more bearable. Polar bear club, anyone?
  2. Infrastructure — Even though we may be a sprawling metropolis with many different cities, I will say that Cleveland has the benefit of a well developed system of roads. If you are so inclined, you can also take an AmTrak train to more destinations than you can from Austin (more track = more destinations…but to be fair you can get to most any city if you sit on a train long enough).
  3. Proximity — This was another nice deciding factor, both in where I went to school and why I wanted to move back. I can easily drive home to Buffalo in 3 hours, can drive to Columbus in 2.5, can drive to Detroit in 2.5 if I’m feeling feisty and can get to Chicago or DC in about 6. This compared with Austin having a 3 hour drive to the next biggest city (that I didn’t want to visit anyway) and a 12 hour drive to get out of the state.
  4. Airport — Similar to above, sometimes you just want to get out of town. If you can’t drive, you might as well fly. And if you’re going to fly, you might as well fly out of a hub. Even though continental decided to cut back their flights out of Cleveland, we have a great place to fly out of to get to some warmer destinations in those bleak winter months.
  5. Home Prices/Cost of Living — Thanks in part to our bozo friends in the finance industry and the overzealous DIYer house crowd, the housing market isn’t doing too hot right now. However, if you’re looking for a house, this is a great time! House prices and general food prices make for a much lower cost of living than many parts of the country, especially those with similar populations to Cleveland. Sometimes this is offset by lower taxes, but your consumption rate can be a little higher without incurring as much cost.
  6. Renewable energy — There is a lot of wind out on Lake Erie. This primes the region for becoming one of the premier renewable energy markets as we move forward with attempting our energy independence. The Great Lakes Institute for Energy Innovation is a start up at Case Western that could really help to move this forward.

I’m still really glad that I moved back to Cleveland. I only dealt with winter from Feb – April last year, so we’ll see how I handle an entire Cleveland winter. I’m not saying I’ll live in the Great North forever, but that for now, it fits me just right. Keep warm!

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Analog Electronics Learning Life Work

What is an engineer?

I’ve been having what some would call an identity crisis. How, you ask? I’ve been working on digital electronics.

*GASP*!

I found out that in the early 90s and even earlier, analog engineers routinely switched from working in the analog domain to the digital domain…because it was paying really great. Not only that, most analog engineers had the expertise to do what most early digital engineers were doing (basically stringing together a lot of digital gates in DIP packages). It wasn’t until later that digital engineers started acting more as programmers and VHDL/Verilog experts.

So why do I bring this up? Because I’ve been thinking about the versatility required from engineers in general, not just analog or digital engineers. Routinely engineers are asked to switch modes or tasks or careers in order to get a job done. It’s not that other professions are never asked this; it’s just that the chameleon-like requirement placed on engineers seems to define the profession. Allow me to explain.

What is an engineer?

An engineer puts theories into practice using available devices and elements. They create new products and pass on knowledge through design iterations and trial and error. Their work should be directly applicable to the real world (sometimes in the form of an end-product, sometimes not) and hopefully able to be reproduced successfully in the same form for multiple parties (mass manufacturing). Engineers are often rooted in math and science but require a wide range of skill-sets in order to properly construct an end product.

I think it is important to note that an engineer is different from a scientist, although the line can often be blurred (especially when looking back at the inventors of the early 20th century). In modern times a scientist is usually tasked with pushing the barrier and finding new theories and concepts. This means that the concept will not necessarily be available in product form right away (although this is not always the case), as the product form must be iterated upon and improved for production.

Another interesting point is how the above definition manifests itself in higher education. When I was in school, the focus was definitely on making engineering scientists, that is engineers who are taught to research new methodologies and concepts with the final product in mind. There was much less focus on using existing products (i.e. discrete transistors) to create something new or to solve a problem. I do not think that it is a huge problem, as some of my classmates went on to work on their Master’s degrees or to work in research labs. The rest of us trying to break into industry were a little more strapped on what is expected from an engineer. Let’s go over what some of these things might be.

  1. Flexibility — This could be a theme of this article. Engineers have to be flexible and think on their feet. Again, I’m not saying scientists and other professions do not have to do this, only that it is required for many engineers. I went into my first job (working in a fab) as an electrical engineer student and ended up looking at chemical reactions and doing process engineering. The company I worked for didn’t want an electrical engineer, they wanted and engineer, someone they could teach their methods to and who could pick up the nuances as quickly as possible. I think it’s also important to note that they didn’t just hire engineers, they also hired scientists (don’t worry, I like scientists).
  2. Science and math knowledge — No surprise here, you have to know the basics in order to really get going in the field. However, I think that the interesting thing is that the basics is usually the majority of what you need. I used Ohm’s Law more often in practice than I use the knowledge of how to do the third integral of a sphere.
  3. Design re-use and not trying to re-invent the wheel — This was actually the reason I wanted to write this post, to point out that engineers often enter the field thinking they will be designing every piece of a system from the ground up. First off, this is irresponsible. The industries would never have standards if every engineering firm was trying to redesign a buck-boost converter everyday. Instead, engineers use optimized solutions available from vendors. Not only does it help standardize, it saves time.
  4. KISS — This directly relates to the above point. You have to keep it simple, because there are only 24 hours in a day. I have claimed to be a system designer before (or at least will be). To design a full system, you have to look at the simplest and fastest solutions because they are often the best and most elegant solutions. Not only that, if you don’t do it as fast and simple as possible, someone else will, and then you’ll lose out on a customer, contract, etc.
  5. Learning is pain — Even though continual learning is one of the main reasons I got into engineering, it’s not always fun. It’s not a great feeling when someone asks you to do something and then you have to slink away because you have no clue how to do it. Hopefully you’re slinking to go learn about it and not running away, but that is dependent on the person. The point is, learning is a difficult process and we really learn the most when we’re in situations that stretch us to the limits. In my experience, I always learned more in classes where I worked to get a C than in the ones where I breezed by and got an A.

Engineering is a field I entered because of the myriad things I could work on throughout my career. I did not switch to the digital domain for the money. I switched to digital work because I was asked to and it has been really interesting so far. Programmable logic is something I’ve worked on in the past and something I’m sure will become more prevalent in the workplace as design requirements become more stringent and timetables get shorter. If you are an engineering student or an aspiring engineer reading this article, I would highly suggest the profession (just make sure you note the above points). If you’re an experience engineer, please feel free to leave your experience in the comments. Thanks for reading.

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Analog Electronics Blogging Learning Life Supply Chain

A quarter century retrospective

When I started writing on my blog, I promised myself that it would not be about personal issues (“my roommate won’t pickup his socks!”) or rants about everyday happenings (“The people at the grocery store are slow!”). But I feel that reviewing the past 25 years of my life is good from a historical perspective and in terms of this blog so readers know more about where I’m coming from.

I am constantly amazed at how lucky I have been. I was born a white middle class male to loving parents and into a great family that encouraged my academic and intellectual achievement. I was also born in the United States of America, in an English speaking community that was voted one of the safest in America throughout my childhood. I’d say this already puts me in the top .1% of the world in terms of being dealt some great cards. Add to that the opportunities I’ve had with the school I was able to attend and the jobs I successfully interviewed for and I can’t think of many better situations. On top of all that, I work at a great company with lots of educational opportunities and I do something I really enjoy.

So not to sound like an Oscars speech, but I would like to thank so many people that made the past 25 years of my life possible. I want to thank my parents and sisters for being there for me and putting up with me. I’d like to thank all of my teachers throughout school that encouraged me, especially my high school physics teacher that inspired me to go into engineering. To all of my friends that are kind enough to click on my blog on a regular basis and give me great feedback on all things in my life, not just this blog. To our pound puppy Lola, who licks my face at every available chance and sits next to me whenever I need a canine friend. And saving the best for last, to my beautiful and brilliant girlfriend, who encourages me every day and loves me even when I’m writing about electronics and trying to explain it to her at 11pm.

That’s all for now. I thought one mushy post interspersed with serious posts wouldn’t be too bad, so I hope you enjoyed. Getting older always seems to have a stigma of life going faster and getting more hectic, but I think of it as more opportunities for learning and meeting new people. I’m sure this year will be another great one. If not, at least I can now rent cars with out that silly under-25 surcharge. Woo!

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Health Learning

The Brain

My friend Trevor has an intriguing post about methods of mapping the brain. This is of interest to me because of how I have been reading “The Singularity is Near” by Ray Kurzweil. Trevor talks about research into “seeing” water flow in the brain, as opposed to glucose or electrical signals or bloodflow. It’s a really cool idea to help understand how the brain works and how it could help humans relate to the world around them.

So why am I interested in the brain? Well, as Ray says, mapping the brain will result in technology beyond anything we could ever imagine for future technology. Using the biologically evolved model of the brain will allow us to leap past prior research in digital and analog technologies to create more advanced computers sooner. This will eventually allow for humans to choose to either become hybrid (biological/machine) beings or even completely machine beings, with transferred knowledge from the biological counterparts. This is also the idea he refers to as “The Singularity”…when human intelligence is surpassed by machine intelligence and machines begin to evolve on their own. Not to worry, he also claims that the machines will consider us “their biological forebears” and they will respect us (and not dominate us and turn us into batteries).

For more reading on/by Kurzweil, be sure to check out The Law of Accelerating Returns, upon which he bases many of his arguments. Some of the ideas he has are pretty radical and optimistic, but they are definitely possible in this lifetime. If you’re not interested in that, make sure you read Trevor’s post (or an part of his blog), it’s quite intriguing.

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Learning Life Politics

Conformity vs. Individualism

The other morning I heard a great story on NPR about people in China and their interest in basketball. I was really interested to learn how they believed basketball allowed them to express their individuality. One of them dreamed out loud of being able to dunk and how this was their ultimate dream of freedom.

Aside from the question of how many different ways there are to dunk, it got me thinking about Chinese culture and how it has contributed to their success over the past 8 years or so. It is no secret that the Chinese culture, and specifically the government, stresses conformity. One might think that this would hinder the technological progress in China, but they are quickly becoming a technology leader in the world (it is important to note that a good deal of the continued success of China is companies outside the country driving progress…but not all of it). Add to that how more and more design work is being offshored, due to the low cost and higher supply of design engineers. A slew of questions have popped up in my mind when I think about these kinds of things.

Does conformity hurt a culture?

I would argue that when it comes to academics and business, conformity helps. In school, this is obvious. If you are in a classroom with 50 other students, every student is expected to know that 2 + 2 = 4. Sure, this is a simple example, but the academic system is usually based upon reaching a solution that someone else (the textbook, your teacher, the government, etc) wants you to reach. Further, the extremely competitive nature of academia in China has parents encouraging this behavior, even outside the structures of academia (no, I am not suggesting that 2 + 2 does not equal 4, nor that you should tell your teacher so to be unique, just that conformity can travel beyond the walls of a school). Academic stress happens in America too, I just feel like it is more ubiquitous in China.

What about in business? This too has some benefits. Think about a production line in China, cranking out iPod after iPod, all made to be the exact same, with the outliers and the bad production techniques tweaked to remove these expensively bad units. The faster each unit can be made the same, the cheaper that unit will be, and the happier the company selling it will be. The concept was created in the wake of World War 2, when the Japanese began to focus heavily on quality control; today, the Chinese benefit from these methods of conformity.

So business and school both seem to be havens for conformity. But what about situations that require some ingenuity? What happens when the product that is made so fast and becomes so cheap and ubiquitous that the public is clamoring for a newer and shinier device? (an iPhone instead of an iPod, for example) Who will create the technology that will drive the next revolution? What about when there are students that rise to the top of their class and go on to get a PhD? What happens when the smartest student goes to the best school and gets the highest degree possible after conforming to all the standards placed before them? Then they stare out into the abyss and try to figure out something new, only to realize that no one is there telling them what they need to figure out. I’m not saying this happens, only that it is an interesting scenario and it begs the question: is absolute conformity a good thing?

Is the academic system set up for failure eventually?

This is an extension of the above idea about PhD students. I know many PhD students (in the US) who tell me about their research being only that which their advisor wants. Further, while they are working on their research, they are hoping and praying that there are not any other students about to publish similar results as their own. Perhaps this is why we see more PhD students who are from outside the US (studying at US schools) or are getting PhDs at international institutions–because the fastest paper published is the most important, not the most creative. Perhaps the conformity aspect of academia extends beyond the simple math equations into the upper echelons of higher education. I think the scariest part is the students who eventually become the teachers. If you think about the rigor involved in obtaining a professorship these days, it can include 1 or more PhDs, multiple post doctorate positions and continual paper publishing throughout one’s career. This basically means that the most astute students of the system (those that best navigate the conformity requirements placed upon them) are the ones that become the teachers. These same people then expect the same (or more!) out of the rising students. One has to wonder when this sort of thing will stop.

Another point about the academic system that confuses me is whether or not the students who exhibit some amount of individuality are more or less successful. I would like to think that those with bright new ideas rise to the top, but I am not so sure that this happens. Perhaps instead the ones that conform the quickest and those with the best advisors do the best. Personally, I have never heard of an academic phenom that did not have a spectacular advisor guiding them through the world of academics.

What is individuality?

Well, the idea is that an individual is capable of defining themselves as different from all other people. Does this happen very often? No, of course not. Even this article I am writing now has been conceived and written about many times over. But I view individuality as the opposite of conformity; it is bucking the norm, even if others do too (some small amount of them, of course. If the majority buck the trend, it becomes the new trend).

How does individualism affect creativity?

Creativity is a nebulous and fickle thing. Further, I don’t think that individuality breeds creativity; instead, I believe creativity breeds individuality. This is important to engineering because without creativity, engineering would essentially stop in its tracks. There would be no new methods, no new products, no intellectual progress. Most importantly (and realistically), there would be no financial gain and therefore no more funding to teach and advance engineering. Of course this also extends outside of engineering; art programs, humanities, economics, language (?)…none of these would be funded if there was no creativity and new ideas. Instead, the money would focus on getting the best value from what is already being made. If this is the case, Seth Godin points out not to follow the money.

Does too much individualism breed a sense of entitlement?

I think it’s important to view the other side of this issue. What happens when students are given the freedom to express themselves and the means to do so? In the extreme cases, I think that students are more prone to laziness, replication (copying others) and a sense of entitlement. Let’s look at an American student as it is interesting to contrast the difference from a Chinese student. Many newly graduating students are demanding higher salaries, more responsibilities and have less experience. Some people justify it (and rightly so), but does that mean we’re worth the more than our last generation? I’m not so sure.

C’mon people, of course the extremes of conformity and individualism will have their faults. Of course there will be some mixing of the two that will produce the best engineers and the best students. However, I would really love to hear from you about your opinions on individuality and conformity.

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Analog Electronics Learning

How an op amp works — Part 2

As promised, this post is a follow up post to explain the real-world behavior of an op amp. Here we will continue to anthropomorphize op amps in order to better understand their behavior and what they “want” to do. Also, we will look at some more complicated (but common) op amp configurations so that they are easily recognizable. Let’s begin.

First, let’s look at the symbol for the op amp:

Whoa-ho! What the heck are those? Last time, there was only 3 lines coming out of the triangle and now there’s five! They’re multiplying!

Really the “D” and “E” inputs are the power inputs to the op amp. This means we are no longer simply dealing with the “ideal” case and are now going to look at the behavior with some realistic expectations. I know that when I was first learning about op amps, I was perplexed by this idea. I thought, “Well what is the point of putting power into an op amp? What do I get for it?” The idea is that as long as the signal at the input (or more accurately the difference between “A” and “B” is smaller than the power at the “D” and “E” terminals, then the op amp can amplify the signal. This gets very useful once you start encountering signals that change over time, or AC signals (as opposed to DC signals). Let’s look at this idea below:


Special thanks to CoolMath.com for the graphing program!

On the top left, we see a SINE wave, which is one of the simplest time varying signals there is. Amplifying this signal would not shift the signal, but instead would make the entire range of the signal larger. If we used a 4x amplification, then we would get the top right picture with the larger signal. Notice in the bottom picture the overlay of these two signals. They do not SHIFT up, but instead look like they are stretched. The easiest way to think of all this is at the extremes. If in the first picture the highest point was 1 and we had 4x amplification, then the output would be 4. However, the middle point is 0 and that multiplied by 4 is still zero. Hence the reason the overlay shows the extreme highs and lows being “stretched” the most. Also, it is important to note that these are analog signals, so EVERY point in between the extremes is being amplified.

The power coming into the op amp also restricts how much the op amp can amplify a signal. Not only that, but sometimes you don’t even get to go to the limits! Say you have +15 volts attached to “D” and -15 volts attached to “E” (most op amps have lower voltages these days but +/- 15 volts still happens sometimes). Now let’s say you have a 1V signal coming into a non-inverting amplifier (shown below). The gain on this amplifier is set to 15 by making the top resistor 14 times less than the resistor connected to the ground (non-inverting amplifiers have a gain of 1+R(top)/R(gnd)). So our 1 volt signal is placed at the non-inverting input (the plus) and the op amp says “15 volts, coming right up!”. Ah, but the op amp doesn’t quite have it. The op amp outputs 13.4 volts are so and then stops. “But WAIT!” you say, “why can’t this op amp output as much as I wanted? The ideal ones can output INFINITY. Can’t I just get one of those?” The short answer: no, you can’t. Op amps have internal protection circuitry that limits how high the input to the op amp can be in order to protect it from blowing up. Additionally, the op amp must consume some of that power in order to actually amplify the input signal; this will be expounded upon in further posts (the internals of an opamp).

The final point in this continuing discussion about op amps, is known as slew rate. Really it is a discussion of how fast an op amp can go and is limited by capacitance. Inside of any op amp, there is a capacitor, or rather a bunch of components that act together as one capacitor. This creates a required charge time for the internals of the circuit (for a more advanced look at this topic, check out the allaboutcircuits.com article on capacitors and calculus). The end result is that the op amp has some limit to how fast it can “decide” what the output should be. If we think back to the signals above that alter with time, we can imagine a situation where they would vary so quickly that an op amp would not be able to keep up. The end result is that a circuit such as the non-inverting amplifier shown above has some frequency above which it can no longer accurately amplify. This is known as the bandwidth of the circuit and has implications in many audio, measurement and communication industries.

This post discussed some of the real world aspects of op amps. The next post will discuss the internals of the op amp, such as the transistor setups. Imperfections in the silicon and the realities of material science will show us that more of the “ideal” op amp model is not possible in every day life; some potential topics are the input bias currents, the voltage offsets across the input terminals and how they can affect everyday circuits.

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Analog Electronics Learning Music

Replacing capacitors on my Wurlitzer 200A electric piano

Things get old. Things eventually do not work anymore. Even the best engineers cannot design a system for part failures (unless they have triple redundant systems, like NASA). It is for this reason, I have decided to document on my blog the tune up of my Wurlitzer 200A electric piano (seen below) as opposed to the usual analog issues in the workplace today.

I mentioned this piano in my post about keeping it simple, namely not replacing EVERY component, only the ones that require an upgrade/replacement. It is a famous piano that can be heard in many types of music, spanning rock, soul, jazz and more.  Similar to the Fender Rhodes, the Wurly can be characterized by a darker, more over-driven sound and a built in vibrato (constructed from a simple oscillating circuit).

There are two components on these boards that need to be replaced the most often. The first is transistors, due to thermal stresses when they are over worked. In the case of my Wurly, the power transistors (seen below bolted to the large metal heat sink on the left) have started corroding, but have also had reduced output due to thermal stresses over the years. The board has upwards of 250 V and these transistors are ready to be replaced.

The other element that commonly needs to be replaced are the capacitors (the purple barrels seen above), specifically the electrolytic capacitors. An electrolytic capacitor is constructed by soaking paper in an electrolyte and sandwiching it between two aluminum plates (then attached to the leads of the capacitor). After about 10 years or so, the electrolyte begins to dry out and the capacitor degrades. Sometimes this can lead to a catastrophic breakdown (think “POP” or “BOOM”) or it can just mean that no signals will get through. Whereas I think of capacitors being frequency-dependent resistors (where the lower the frequency, the higher the resistance), these capacitors instead have resistance at ALL frequencies, due to the fact that the dielectric constant has gone from that of electrolyte to that of air. The final effect of all of this is a poorer sound, especially at the higher frequencies that are supposed to “pass through” a capacitor.

I am also hoping this will take care of some of the “hum” sound (most likely from 60 Hz); I’m hoping this will be resolved once the power filtering capacitors are replaced. I think that the ripple current may be higher since the capacitors have slowly degraded. This will impose the 60 Hz from the wall power onto the signal coming from the vibrating reeds (through the capacitive pickup). I also am wondering if the transformer (below) requires replacement, but I think I will replace the capacitors and transistors first.

That’s all for now, I will update more as I actually replace these capacitors. For now, enjoy the pictures and the sound samples (above links to Last.fm).

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Analog Electronics Learning

How does an op amp work? How do I use an op amp? — Part 1

How does an op amp work? How do I use an op amp

These are questions that I have asked at two periods in my life. The first time was in my introductory circuits class and around that time I really didn’t care (beer was a priority). The second time was when I dove headfirst back into analog electronics for my new job and had to re-teach myself a lot of things. I really appreciate the opportunity I had to re-learn everything because the second time around, I think I got it right.

OK, so let’s start simple. What is an op amp? Whoa, loaded question. For our purposes here (and just for now), let’s say it’s just a symbol.

Figure 1: Just a symbol folks, nothing to see here

To keep things basic, the A & B points are the input, the C point is the output.This symbol is an IDEAL op-amp, meaning it is impossible to construct one and really the expectations for the op amp are unrealistic. But this is the internet and we can do what we want on the internet, so we’ll just use the IDEAL op-amp for now.

Figure 2: Inverting Ideal Op-amp
Figure 2: Inverting Ideal Op-amp

OK, so now you know what the symbol is, but what does it mean? Well, the idea is you put two electrical signals into the inputs then the output changes accordingly. It takes the difference between the inputs and amplifies it, hence operational amplifier, or op amp. You may have noticed that input A has a minus symbol and input B has a plus symbol. So let’s say that the input to the minus, or INVERTING, input is 1 (for simplicity’s sake…this site is about analog so that value could be ANYWHERE from 0 to 1 or higher! Just thought I’d mention that). The input to the plus, or NON-INVERTING, input is 0. Now the op-amp is in an unbalanced state. The device is designed so that when this happens, the output goes as negative as it can. For the ideal case, we say this is negative infinity, but that’s not really possible. More on that later.

Figure 3: Non-inverting Ideal Op-amp
Figure 3: Non-inverting Ideal Op-amp

Conversely, in figure 3, if we put a one on the non-inverting and a zero on the inverting input, the op amp output would go high, infinity for our purposes here. The important thing to know is this:

The op-amp always “wants” both inputs (inverting and non-inverting) to be the same value. If they are not, the same value, the op amp output will go positive or negative, depending on which input is higher than the other.
(Throughout this article I will continue to anthropomorphize op amps…best to get used to it now)

Alright, so how do we use this in circuits? If we wanted to find out if two signals were different, we could tie the signals to the inputs of the op amp, but then the output would go to infinity. This would not do us any good. The answer to this and many other questions in the universe is feedback. We are going to take the output and tie it back to the inverting input. Now the circuit looks like this:

Figure 4: A buffer
Figure 4: A buffer

First, we assume that the circuit has all points start at zero (point A being the most important). Next, we put a value of 1 (like the picture in figure 2) at the “B” non-inverting input. “WHOA,” says the op amp, “THIS AIN’T RIGHT!” So now the op amp puts its output to as high as it can, as fast as it can. This feeds back from the output (“C”) to the inverting input (“A”). So as the output moves closer to 1, the op amp is happier and backs off the output. When the input at A is the same as at B, the op amp is happy and stays there (but maintains the output of 1). The key here is that the op amp moves as fast as possible to get both inputs to be the same.

Why would someone use a buffer? Well that brings us to the next point about op amps, specifically ideal op amps:

Ideal op amps have infinite impedance (resistance) at their inputs. This means that no current will flow into the op amp.

A common use for a buffer is to supply current to another stage of a design, where the buffer acts as a gateway. So when the buffer “sees” a voltage at the input (“B”), it will output the voltage at “C”, but will also drive that voltage with current (as much as you want for an ideal op amp). This would be useful if you have a weak signal at the input, but want to let some other part of a circuit know about it. Perhaps you have a small sensor that is outputting a small voltage, but then you want to send the voltage over a long wire. The resistance in the wire will probably consume any current the sensor is outputting, so if you put that signal through a buffer, the buffer will supply the necessary current to get the signal to its destination (the other end of the wire).

What if the signal coming from the sensor is too small though? What if we want to make it bigger? This is when we turn the op amp into an amplifier, using resistors. One of the more common ways of doing so is using the inverting input, shown below:

Figure 5: Inverting op-amp
Figure 5: Inverting op-amp

Let’s go over what we know about this circuit. We know that the op amp wants both inputs to be the same. We also know that the non-inverting input is zero (because it’s connected to ground) and so the op amp will want the inverting input to be equal to zero (sometimes known as a “virtual ground”).  In fact, since the op amp has feedback through the top resistor (squiggly line if you didn’t know), then the (ideal) op amp will output just about any current and voltage in order to get the inverting input to be equal to zero.

So now our situation. A dashing young engineer hooks up a voltage source to the point “IN” set to 1 volt. This creates a voltage at the inverting input. “WHOA” says the op amp, and then it begins to output a voltage to make the inverting input point equal to zero. Since the input is 1 volt the op amp decides it better do the opposite in order to make the inverting input match the non-inverting input of zero. As fast as it can (infinitely fast for an ideal op amp), it outputs -1 volt. The inputs are both zero and everything is right in the op amp’s world. What about current though? We remember that current cannot flow into the op amp at the inverting input, so any current will be flowing through both resistors. If we have 1 volt at the input and a 1 ohm resistor at the input, then we will have 1 amp of current flowing (according to Ohm’s law V=IR). So when the op amp outputs -1 volt across the top resistor, there is a -1 amp going through it (assuming it is a 1 ohm resistor). The currents cancel each other out at the inverting input and the voltage then equals zero. The place where the currents meet is sometimes called the “summing node”. This is a useful representation when dealing with currents as opposed to voltages.

For the last part of this thought exercise, let’s look at a situation where the resistors at the input and at the top of the circuit are not the same. Similarly to above, the same dashing young engineer puts 1 volt at the “In” node. The resistor is still 1 ohm, so there is 1 A of current flowing through to the summing node. The op amp once again sees this 1 volt and once again says “WHOA, I’m unhappy about this” and starts outputting the highest voltage it can. However, in this situation, the top resistor is now 4 ohms. In order to create the -1 amp that is required to cancel the 1 amp going through the input resistor, the op amp must output -4 volts (remember V=IR).  We see that for an inverting op amp configuration, the ratio of the resistance of the top resistor to the bottom resistor determines the gain, or a multiplication factor from the input to the output. Also notice that the output is negative for a positive input, confirming that this is an inverting amplifier.

That’s the basics of it. Check back here for more about op amps, because there is a lot more to be said. Future posts might include other op amp configurations, design considerations and even the dreaded “REAL WORLD”, where the ideal op amp no longer exist.

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Categories
Analog Electronics Learning Work

My name is Chris…and I’m an analog engineer

Or am I?

I read technical publications on a pretty regular basis. And more and more lately, especially with the lull in the economy, I read about how jobs are going offshore or overseas. Sure, this concerns me, I’m human! Plus, I’ve inherited a worrisome nature from my mother. But I’ve had the fortune of reading a lot of articles about how analog engineers are in short supply. Even how they’re moving into green technologies!

“Yahoo!” I think.

But wait a second, what’s all this.

I have read how analog engineers are hard to find. I know that the experience is both rare and valuable. But what kind of analog engineer I ask? Most of the articles I see are regarding silicon design and regardless of what I have done in the past with Samsung, I have never had the opportunity to look at analog design on silicon. And I have to wonder, am I allowed to call myself an analog engineer? I’m going to go with yes.

Here’s why:

  1. I know how to use an op amp
    • That’s one of those triangle things, right? I use these all the time and they are the basis of any analog engineer’s work. I feel like the main difference between myself and an engineer designing in silicon is I go out and buy a part for a dollar, they just go into a CAD library and plop one down in their design (and maybe mess around with it to get the specs they need). Anyone out there know if this is true or not?
  2. Yes, I even know how a transistor works
    • Granted, my silicon level knowledge is a little weak (I never liked calculating the number of electrons flowing through a PN junction…it just seemed so anti-Heisenburg). But plop an NPN transistor down in front of me (or a symbol of one), and I think I can fare pretty well. A great test of basic knowledge is in the chapter “A New Graduate’s Guide to the Analog Interview”. See how many of this limited passage you can get right.
  3. I know how to put it all together
    • There is a lot more to analog electrical engineering than knowing equations. A good example in my specific branch would be talking to vendors and getting pricing on parts. There are some big swings that can occur on prices of parts! Another example of putting it all together includes other aspects of design you might not think about. How about supporting a product 10 years down the line? I haven’t done this one personally (given my relatively short career thus far), but I’ve had to help out with some designs where the original designers were no longer around. And I’ll tell ya, some of those components were not meant to last! Needless to say, there is a lot of other tasks out there than just thinking up a circuit.

So even though I don’t intend on changing what I call myself anytime soon, I will clarify my skills. I am an analog system designer. Is that too far off? No, I don’t think so. Even the limited amount of design I’ve done really fits into that category. I have strung together a lot of components in order to create systems capable of processing analog signals. Further, sometimes the available system components (op-amps, buck/boost converters, etc) need to be made with passive components because of individual system constraints (meaning the stuff that vendors offer just don’t do what we need them to). I think more and more though, the industry will go towards system designers, simply because of rising costs. As systems get more and more complex, economies of scale mandate that people specialize in order to win business. We have also seen trends where chip makers are beginning to reach practical limits of how much better they can make certain devices (op amps, for instance). As such, we’ll see that the chip makers put more and more functions inside of chips.

So maybe one day I will work for a chip maker, trying to shove more components into a package? I enjoy the thought of creating a component that thousands if not millions would use. Perhaps this will be all that will be left to do? I’d obviously like to start learning it all before it’s the last frontier of design. Perhaps one day our tiny cell phones and other gadgetry will be nothing more than a screen and a single chip with every required function in it. But if I’m not making the screen or the chip, hopefully they’ll still need someone like me to hook that chip up to that screen. Who knows what the future will hold?

One final (and mostly unrelated) note I’ve been meaning to put in a post; writing about analog issues seems to be as good a time as any.  I’m sure at least one or two people noticed (probably not), I changed the tag line on my blog from “Chris Gammell’s Renewable Life” to “Chris Gammell’s Analog Life“. A few reasons: I think it makes more sense (I’m not Hindu, so I don’t really think life is “renewable” per se); the world around us is truly analog (as much as marketers would have us believe that music is “digital”); and to be blunt, I like the sound of it better.  Plus, I doubt too many people will be like “Wait, where is my favorite site??? Ohhhh, it just changed names…”.  This doesn’t mean I will stop looking at issues facing renewable energy, just that I want the focus of my site to be on analog.

That’s all for now. Chris Gammell, analog electrical engineer, out.

Categories
Blogging Learning Life Supply Chain

Alltop

Welcome Alltop visitors!

I am unfortunately becoming an information junky. I have friends in DC and they have mentioned on multiple occasions that this is the norm at least in our nation’s capital; that people consider being news-knowledgeable to be a social status. Well, I guess I’m part of it; I love being connected and being in the know, especially about engineering and analog electronics. Don’t worry though, I’m still pretty low on the social ladder and I like it that way :).

Alltop.com is a news aggregator community and I am now a part of that community. I found out about it from a badge on Penelope Trunk’s blog (my favorite for career related issues) and I requested to be a part of the community (yes, I’m that guy). It was started by Will Mayall, Kathryn Henkens, and Guy Kawasaki. (EDIT: I had confused Guy Kawasaki and Robert Kiyosaki. Sorry!) As far as I have read, all are serial entrepreneurs and Alltop is a great start.

Anyway, if you are interested in finding a lot of information in one space, this is it. I kind of think of it as a Google Reader, but someone else is filing all the stories into neat little compartments. You’ll find my site under “E” for engineering, but I’m thinking about lobbying them to file me under “N” for nerd. We’ll see. Enjoy Alltop!

PS. Fun fact about Alltop.com…the “Moms” feed has the most of any, so they have to limit the story listing. Who knew there were so many Moms out there blogging and writing? (well, Moms apparently…and Alltop.com)