Category Archives: General

Amp Hours of Aural Entertainment

Just this week I was in a conversation with someone and I found myself saying “Hey The Amp Hour interviewed someone in that field!” only kill the flow of the conversation with Google searching for the episode. Turns out it was Episode 71 with John Edmond of Cree.

I started listening to The Amp Hour way back when the number of episodes could be counted your fingers in decimal, not binary. Since then I remember the gist of a lot of shows but I haven’t gone back and replayed too many which is a shame since Chris and Dave have done a lot of really cool interviews as the show has grown. After that conversation I figured if I can go back and reread books at any point why not do the same with podcasts? So that’s my aim for the short-term, re-listen to some of the interviews that have stuck with me over the years. It will shock no one that a lot, but not all, of them are analog focused.

#54 – An Interview with Jack Ganssle – Embedded Elchee Epexegesis

#60 – An Interview with Joe Grand – Pancyclopaedic Prototyping Polymath

#71 – An Interview with John Edmond – Luciferous LED Lucubrator

#77 – An Interview with Dr. Howard Johnson – Winsome Waveform Wizardry

#84 – An Interview with Bunnie Huang – Bunnie’s Bibelot Bonification

#95 – An Interview with Øyvind Janbu – Feracious Fabless Facilitator

#115 – An Interview with Dr Greg Charvat – Watcher of Wraithlike Walls

#117 – Interview with Alan Wolke – Undulating Utensil Utility

#119 – An Interview with Dr. Kent Lundberg – Luculent Linear Legacy

#129 – An Interview with Brett Fox and Dr Jeroen Fonderie – Device Doubling Decretum

#133 – An Interview with Ron Quan – Tenacious Transistor Teacher

#135 – An Interview with Mike Harrison – X-ray Examining Xenogogue

#144 – An Interview with Bob Davidson – Hoodied HP Hijinks

#157 – An Interview with the SparkFun Team – Efficacious Engineering Ensemble

#165 – An Interview with Henry Ott – Forced FCC Filtering

#171 – An Interview with Forrest Mims – Snell Solisequious Scientist

#180 – An Interview with Dave Taylor – Multi-talented Meter Maker

#181 – An Interview with Dave Vandenbout – Xceptional XESS Xenagogue

#187 – An Interview with Elecia White – Wirewove Worshipping Wookieist?

#196 – An Interview with Mike Engelhardt – SPICE Simulator Synteresis

Assuming I’m doing routine tasks at work that don’t require me to be in full on troubleshooting mode I should be able to keep occupied for a few weeks at least. If anyone can think of a good interview I forgot or just wants to share their favorite interview with me I’ll be happy to add it to the list! Also, I’d like to somehow bundle all these files into one convenient download for whoever wants them but I don’t know how to go about doing that easily unfortunately. Please clue me in if you could be so kind.

Update: Dave pointed out to me that I could always just use The Amp Hour App to easily find the shows I’m looking for. Doh! I’d forgotten all about that. Check it out and support the show!


Office Tomfoolery

So Monday at work I successfully pulled a prank on the designer for the part that is currently occupying the majority of my time. Concept, planning, and execution took about two weeks or so as I had to fit this little side project in around my real work obviously. Ever since the part’s inception this designer had been claiming it was perfectly designed and any errors were clearly the fault of me, the Applications Engineer. He wasn’t being mean or anything, this sort of good-natured rivalry is pretty common between the Apps and Design departments at work, but being that this is my first part as lead apps since starting a year ago meant I got some extra abuse. I figured it would be a good idea to go on the offensive and show everyone I wasn’t such an easy target. My boss, who’s been good friends with the designer for a long time now, thought it would be pretty funny and approved the gag, eager to see how it would play out.

The part is a single phase buck regulator meant for Vcore applications in laptops and ultrabooks. Vcore means that the regulator provides the main voltage rail to the processor, specifically an Intel one in this case as AMD and other processors have different power requirements. My goal was to somehow screw with the regulator, cause the output voltage to glitch and go out of spec, and convince the designer this was a silicon bug and not a board issue. After a little brain storming I came up with the following circuit which could be cobbled together out of various parts in the lab:

Prank Circuit

My Prank Circuit

Without diving down the rabbit hole that is regulator compensation, the comp pin of any buck converter is the output of an error amplifier which connects to a networks of passives going back to its negative terminal (the Feedback pin) and is part of the control loop used to keep the output voltage stable and well-regulated. My circuit would periodically drive this pin away from its steady state operating point. This disturbance would propagate through the chip and result in a noticeable glitch on the output voltage until the compensation loop could regain control and bring the output voltage back into spec.

As phase switches merrily along at the frequency and duty cycle set by the controller it gets divided down by R1 and R2. When phase is high the output of this voltage divider is enough to forward bias the diode and cause current to flow into C1 for a brief period before going low again. C1, which also connects to the positive input comparator U1, charges over time and when the voltage across the cap gets to be higher than the reference voltage present on the comparator’s negative input the comparator’s output swings to 5V. When U1′s output goes high two things happen. One, comp is driven away from steady state through R5 and two, the gate of M1 goes high which discharges C1 below the reference voltage starting the cycle over again.

Prank Sims

Prank Circuit Sim Results (Click to view properly)

There really wasn’t much thought process behind the component values in my circuit; they were determined through trial and error in simulation. I didn’t care how often the circuit would trigger, only that it did and the disturbances it caused would appear on Vout. One of my only goals was to ensure that the resistor dividers wouldn’t draw enough current to interfere with the normal operation of the regulator and cause it not to start up. My second goal was to “break” the regulator just enough to cause concern but not enough to trigger any of various over voltage, current, or temperature protections built into the chip. This is why R5 had to be added; without it comp was driven too hard and the part simply shutdown (there’s no fun in that).

With the circuit idea solidified I headed into the lab to jury rig it into place underneath one of the eval boards. It was a messy hour after work one day, but I successfully placed each component and wired in the various signals and voltages from all across the board. Once things got going, there would be so many cables and probes attached to the board I knew it wouldn’t get turned over until I was ready to reveal what I’d done.

 

Holding my breath I powered up the board after making all the necessary modifications. Surprisingly enough it worked! I hadn’t made any disastrous mistakes when wiring it all up and the resulting waveforms basically match with my sims. All that was needed was some tweaking of R5 to find the right value and I was ready for action.

Cutting to Monday morning, I spent a little time taking scope captures of a good board and my doctored eval board. These were placed in a quick report which I shot off to my boss and the designer right after lunch. To add to the joke I took my clean scope caps using a part from an old rev of silicon and explained how the “bug” was only seen in the latest version of the chip. This caused the initial spark of concern in the designer as we’re currently waiting on a new rev of the chip to arrive from the fab and it was too late to make any changes. After getting some tests to run and tweaks to try, I actually went into the lab and did them! For one I was curious to see if any of them could actually fix the error (they didn’t) and secondly, this designer is pretty hands on and likes to come out to Apps Lab quite often. I knew that if he came out to see the glitch on the bench and none of his changes were made he would get suspicious. Fortunately, or unfortunately, other obligations kept him away for the day and he never came out to see the problem until the end of the day.

After running the initial list of tests the designer gave me I had a flash of brilliance that really threw him for a loop. I took a series of scope shots at each of the four switching frequencies our part could run at and varied the value of R5 at each one. Now I had created a problem that went away as switching frequency increased and could explain why we hadn’t seen this issue before as the majority of our testing had taken place at high frequency up until this point! Bingo.

By the end of the day, the designer was pretty much stumped. He’d done an initial check of his schematics, couldn’t spot an obviously fault he made, but thought it was a mistake somewhere in the core of the modulator. He told me that at this point he essentially resigned himself to hoping the new version of the chip came out okay and whatever changes he made would happen to fix this (remember it’s too late to make changes now as the part’s being fabricated).

Right afterwards I called him into the lab saying I’d found something interesting and he should come take a look. When I showed him the circuit on back of the board he didn’t get it at first. He asked why all this crap was added and what did it fix? I couldn’t hold back anymore and broke out in a smile and said that I just wanted to mess with him. Slowly realization dawned on him and he started laughing as did my boss and a few other guys in the lab who were in on the joke.

In the end the designer took it really well and thought it was pretty funny. He told my boss to give me more work as clearly I didn’t have enough to do since I could pull these elaborate pranks but mostly he just laughed. I now owe him a round or two the next time a bunch of us go out after work but that’s a price I’m more than willing to pay all things considered. In the end I caused him just enough trouble so he started to sweat but not enough to take him away from any real tasks he had to get done. A well executed prank overall in my opinion. Surely, there’s no way this will every come back to haunt me right?


How to Stand Out & Other Career Fair Tips

A few weeks ago I traveled back to my alma mater to recruit some students for co-op and full-time positions available at various locations throughout my company. For the first time I was going to experience what it was like to stand on the employer side of the booth at a Career Fair. Chris Gammell, the good guy that he is, gave me some tips on getting through the day in one piece which came in quite handy. Fast forward to today and I can tell you that working a Career Fair is exhausting. I had fun and definitely plan on doing it again but I would almost say it’s easier to be the one looking for a job.

Regardless of how I feel personally about working Career Fairs, standing in that Field House all day I did see a few pitfalls that students fell into. Bearing in mine I’m not even close to a recruitment expert, read on for my take on what you the student can do to improve your game, standout, and sell yourself better to employers while attending a Career Fair. In no particular order they are:

  • Check out these tips from Chris Gammell. Go ahead, I’ll wait…
    • His post gives a lot of good advice and I pretty much agree with what he has to say (except for #4 when it comes to candy, that’s fair game) . Following his tips will definitely take you a long way when it comes it impressing potential employers.
  • Format your resume so it’s easy to read.
    • I looked at a lot of resumes during the 5 hours I was the Career Fair, a lot. There were long ones, short ones, pretty ones, and ugly ones. Some with one font, two fonts, red fonts, blue fonts. Okay, maybe that last part was a little bit of an exaggeration but I liked the Dr. Suess rhythm I had going. You’re only talking to an employer for a few minutes at most and those couple of minutes should be a discussion between you two rather than awkward fumbling and pointing as you try to locate and point out some portion of your resume after it’s come up in conversation.
    • Try and keep it to one page with only the most relevant information about yourself on it. Instead of listing every single course you’ve taken in school focus on work experience, skills, and projects you’ve done.
  • Highlight your big accomplishments that make you unique.
    • This goes along with my above point about relevant info on your resume. If you’re an upper level EE an employer should be able to assume you’re familiar with basic circuit theory. Showcasing the EE101 Resistor Divider Lab that everyone in 3 departments has to take is not making you stand out.
    • Have you taken a difficult elective not many others do? Were you also passionate about the work you did in that class? Talk about that instead.
      • VLSI and IC design course tend to really make you jump out to semiconductor companies. I know from both working the Career Fair and from my own job hunting experience. A hard copy of your layout will make even the toughest recruiter take you more seriously.
    • Did you solve a particularly interesting problem on an old internship or co-op? Be sure to mention that if it doesn’t come up on its own.
    •  Work on projects or study topics on your own or as part of a club? Those are both worth their weight in gold when it comes to standing out as it shows you’re passionate about the work you do and are self motivated. There’s also the possibility that a strong interest in your field outside of your required course work can make up for a less than stellar GPA or lack of on the job experience.
  • Be honest about what you like.
    • Our table was cluttered with all sorts of circuit boards and demo projects. Some were eval boards showcasing parts in our catalog and others were customer boards that had parts from our company designed in. Telling me one minute you like to design and work with electronics is one thing. However, if the next minute you’re not so much as batting an eye when I dig out an old intern project that has you doing just that doesn’t bode well for you. If you’re not thrilled about working with hardware (or software, or embedded systems, or MEMs, or whatever) don’t lead the recruiter on. It just wastes everyone’s time and it’s easy to see through.
  • Introductions are important.
    • You may not be the most outgoing person in existence and that’s okay. What’s not however is looking at the ground and mumbling your name during an introduction. The venue is going to be noisy to begin with and if the recruiter can’t catch your name after the first or second try it’s going to be tough not to put your resume in the pass pile. It’s sad but it’s true. 
    • Speak up, speak clearly, make eye contact, and have a firm handshake. It’s  simple things like that which can make you stand out after a recruiter has been on their feet all day dealing with Low-Talkers.
  • Come across as someone who is fun to work with. 
    • There was a second year student looking for their first co-op who whipped out a plate of homemade cookies and offered  them to all of us at the booth after we were done talking to him. That’s good stuff. We laughed, thanked him for offering, and once he was gone bumped his resume up a few spots on our list. Do you have to do something that extreme? No, but giving the impression working with you isn’t going to be hell counts for a lot.
  • Do at least some research as to who is looking to hire someone with your skills.
    • I work for an analog IC company. If you didn’t know that going into the Fair it was printed on our gigantic sign and the table was cluttered with all manner of circuit boards. The Co-op Office website had the list of majors we were interested in and so did the packets of info each student got upon entering the Fair. Odds are good we aren’t going to have openings for astronomers if all our material screams EE’s Wanted (yes, I was actually asked that).
    • If a company catches your eye you didn’t know existed until right that moment it’s okay to approach them and ask for more information, that’s why they’re at the Career Fair. There is however, a right and a wrong way to go about doing it.
      • Student A: “Hey, I’m an EE. What positions are available?” Isn’t going to cut it when there are people out there who are actually interested whatever the company does.
      • Student B: “Hi, my name is … I don’t know much about your company but I see your booth is covered in circuit boards. I really like working with electronics and would like to learn more about possibly getting a job with you guys.” This is almost word for word how a student introduced themselves to me at the Fair  and it’s a great example of how to approach a previously unheard of company.
      • Needless to say Student B got much more of my time than Student A did.
  • Don’t let employers push you around.
    • This tip is just something I encountered back when I was a student and want to pass along. On two occasions I had recruiters telling me how I was going to change my whole co-op schedule around and what courses to take to work  for them, after we had already established they stretched the truth about having hardware positions available. In these cases I politely interrupted the recruiter, said I wasn’t interested, and asked for my resume back if they hadn’t written on it (yes, it’s okay to do that once in a while).
    • Just as you shouldn’t waste an employers time they should be wasting yours. It’s better to spend your time  with companies that might actually have something for you (see also point #1 from Chris’ post).

Well there you have it, my take on Career Fairs and how you can avoid some of the mistakes that I witnessed during my first recruiting assignment. As I go out to other colleges and spend more time evaluating potential full-time and co-op candidates I’ll come back and revise and add to the list.

 Got any other tips for student job hunters? Did I miss the mark on any of my points? Just have a humorous Career Fair story from either side of the booth? Sound off in the comments.


Surgeon – My Fallback Career

So I was knuckle deep in a crazy board rework today at work trying to fit a 1206 cap where it didn’t belong because it was left off the schematic and consequently the layout. About halfway through I realized that the rework I was performing required a pretty steady hand, like I imagined a surgeon would need. I chuckled to myself and tweeted that if being an EE didn’t work out I was going to become a surgeon as all the reworks I’ve done over the years count as practice.

Satisfied with my wittiness I pocketed my phone and continued on modifying the board. That would be the end of the story if my brain would ever let anything go. Instead I kept thinking about surgery the rest of the day and realized that actually, EEs are quite a bit like surgeons when you think about it.

  • Operating Room & Table = Lab & Bench
  • Scalpel = X-acto Knife
  •  Heart Rate Monitor, O2 Monitor, etc. = Oscilloscopes, Multi-meters, etc.
  • Cauterization Tool = Soldering Iron
  • Nurses = Techs
  • Tweezers, Hemostats, Cotton Swabs = Tweezers, Hemostats, Cotton Swaps
  • Isopropyl Alcohol, Antiseptics = Isopropyl Alcohol, Board Cleaners
  • Anesthesia = Flux (Just makes the whole process a lot smoother)
  • Microscopic Surgery = Soldering & Scrapping under a microscope
  • Defibrillator = ESD Gun
  • Too much caffeine makes operating harder = ditto
  • Sinus Rhythm = Steady State Response

So I guess all that’s separating me from becoming a surgeon is jargon am I right?


More Vintage Tek Gear

Back in October I posted about some old Tektronix equipment I found at work consisting of a function generator and current probe amps sitting in a power supply chassis. Well after a few more months of rummaging around the various labs and store rooms at work I stumbled across another old piece of Tektronix memorabilia, a Type 576 Curve Tracer. As far as I can tell from perusing the web it dates back to the late 1950′s or early 1960′s. One site, Barry Tech, claims the curve tracer is from 1969 while Vintage Tek simply states the 576 was developed sometime between 1960 and the early 70′s when the series was discontinued. The 576 is also the second curve tracer offered by Tekronix designed with transistors instead of tubes, the first being the 575.

[Update: The guys over at Vintage Tek got in touch with me and as it turns out the 576 first appeared in the March 1969 Tektronix catalog.]

Spec Overview from the datasheet found on Valuetronics:

  • Can deliver up to 220W of peak power to the DUT.
  • Voltage steps can be as large as 1500 V and current steps can hit 20A peak. If you purchase the 176 high current plug-in the 576 can hit up to 200A!
  • Absolute accuracy of 2% of total output including settling, or 1% of amplitude setting.
  • Pulse generator capable of 1 to 10 repeated steps.
  • Built in beta and gm calculator to save the designer from pesky arithmetic

The 576 Curve Tracer in all its magnificent glory. Couldn't find a picture of the insides online sadly.

I think I definitely prefer knobs over touchscreens on my test equipment. Fiddling with this guy just felt great. Not that I want to give up my modern gear completely mind you, I'm just sayin'.

Note the force and sense lines for the collector and emitter terminals. Also this thing could dish out some serious power to the DUT, up to 220W!

Looking on Barry Tech I saw they also provided a link to the 576′s manual you can check out here. Tek was kind enough to provide a complete section dedicated to the circuit description that I definitely plan to check out in my free time. The circuit description section includes pieces on the control loop compensation, logic diagrams, timing charts, and at first glance, what appears to be pretty detailed explanations of it all. Check out Figure 3-6 to see a diagram of the discrete A/D used in the tracer designed with only a handful of diodes and resistors. Supporting the DIY movement before it was fashionable, the manual also contains a complete section on basic maintenance and troubleshooting including where to locate various circuits, key performance specs, and a soldering guide.

Unfortunately I don’t think this 576 sees much action anymore at work. To my knowledge nothing in our product catalog needs to be tested using at the individual device level and if it did it would probably be done using a wafer probe station instead. I’ll ask some of the designers and test engineers if it’s ever used anymore and report back.


Jim Williams, AN13, & Op Amp Wizardry

Not too long ago I was reading through one of Jim Williams’ famous App Notes, AN13, High Speed Comparator Techniques. It’s an older App Note that was published back in 1985 and I didn’t really have a specific reason for reading it other than thinking it looked interesting and I wanted to learn more about comparators. For a comprehensive overview of AN13 I recommend reading Dr. Lundberg’s (aka Dr. Analog) three part summary over on his blog Reading Jim Williams.

The first section of AN13 is extremely informative and makes the app note well worth the read in my opinion. Entitled “The Rouges Gallery of High Speed Comparator Problems” this portion of the app note highlights common pitfalls of comparator circuits including bypassing, ground planes, probe compensation, and much more. As useful as The Rouges Gallery is what intrigues me the most in AN13 doesn’t actually have anything to do with comparators and is found in the first circuit of the Applications Section. The overall circuit is a Voltage to Frequency Converter shown in Figure 16 of AN13 and reproduced below with the part that fascinates me most boxed in red.

What Jim Williams has done is replace the input stage of A1, the LT318A, with a pair of 2N4393 JFETs. These JFETs drive the output stage of A1 via the two Comp pins of the amplifier. A1′s true inputs are shutdown by shorting them directly to the -15V supply leaving the rest of the amplifier free to serve Williams’ needs for this particular application. According to page 8 of the app note this trick was done “for low bias, high-speed operation.”  Now I don’t have a whole lot of experience using op amps with Comp pins to begin with let alone understand their internal architecture enough to hack them like Jim did. As far as I knew something like this wasn’t even possible and it definitely wasn’t brought up in any of the classes I took in school! Needless to say, upon seeing it done here in AN13 I was a little stunned.

After my initial shock I decided to look at the LT318A a little more closely to try to see how Jim Williams had pulled off this neat little trick. Linear Tech is usually pretty good about providing schematics  of their op amps with a description in their datasheets and I was hoping this was the case with the 318. As it turns out, the LT318A datasheet is a bit sparse compared to other datasheets from Linear but fortunately for me it does contain a schematic of the part. Unfortunately for me, it doesn’t appear to be a simplified version and there isn’t a functional description. Looking at the schematic in detail I could tell this wasn’t the basic op-amp architecture I was used to dealing with but I decided to dive in anyways. I’ve copied the LT318A schematic here and marked it up into functional blocks as best as I’m able to but if anyone out there has more info on this op amp or sees somewhere that I went wrong please let me know.

From studying the datasheet schematic of the LT318A I was able to understand more of how Jim’s op amp hack works. Connecting the amps inputs on pins 2 and 3 to the negative rail turns off the differential amplifier, the heart of which are the input transistors Q1-Q4 with Q13 and Q14 being the active loads. As a side note there may be some common-mode feedback on the diff pair but I’m not 100% sure. Thinking about what was said in the app note I would have to assume using two JFETs in place of the input circuit on the op amp would lower bias requirements and cutting out all those transistors speeds up operation of the overall application circuit.

The output from the input differential stage is then fed into what I assume to be a second gain stage  (not sure what Q21 does, this may be a weird folded cascode configuration too). From Figure 16 in AN13, you can see that Jim Williams has the JFET input transistors driving pins 1 and 5 on the LT318A. Sure enough these two pins correspond to the output of the diff pair on the amplifier and feed directly into the second gain stage. Following the gain stage comes what appears to be a Class AB output stage.

I enjoyed this little exercise of trying to understand some of Jim Williams’ techniques. While I may not have exactly figured out how the LT318A works I feel I did understand the high-level thought process behind this neat little trick. I also saw that my BJT design skills are a little rusty and that perhaps I should dust off Gray & Meyer or Sedra-Smith and brush up on the topic. Who knows, there could be a revisit to this post in the future…

Any neat op amp hacks of your own? See a mistake in my analysis of the LT318A? Let me know in the comments. Oh, and Happy New Year!


State of the Fake EE Union

Well hello there. It certainly has been a while since I’ve posted. Sorry about that, between the holidays and submitting a draft of my thesis to my adviser before Christmas I was running around with my head cut off and couldn’t seem to find the time to write anything. Just to keep everyone updated and what not here’s a couple of noteworthy news items:

1) Back on December, 20 I had an article published over on Engineer Blogs about the differences between school and work. Chris and the other EB writers were kind enough to offer me a spot guest writing for their site after I submitted the piece for their consideration. For the time being I will be submitting stories to EB for your enjoyment on a part-time basis and will work up to one day joining the team as a full-time author.

2) Though I’m writing for Engineer Blogs on occasion I will still be posting content here to this blog when I get a chance too. Fake EE Quips will stay more technical in nature (circuits, app notes, etc.) while any stories that I feel relate to engineering as a whole I will publish on EB. I’m currently trying to get a post out here before the new year so be on the lookout that in the next day or so (it’s about Jim Williams and a crazy op-amp trick). I’ve also got some more ideas bouncing around in my head but my lack of a home lab makes it difficult to prototype and test circuits. Hoping to acquire a scope and power supply in the new year but we’ll see…

3) The Amp Hour Bingo will be getting some updates in order to make it easier to win and more fun to play. For those of you who play along like I do I’m sure you’ve noticed it’s basically impossible to BINGO while listening to the podcast. As far as I know I’m the only one who has gotten a BINGO and it’s only happened once. Roel and I brainstormed a bit and came up with a way to place the tiles more efficiently so the most common aspects of The Amp Hour are always used when a board is generated and the rest serve as filler. Other features to add were also discussed including saving a board and posting results Twitter. I don’t know when exactly these changes will be put into place since I’m dead weight when it comes to coding but when Roel finishes them I’ll be sure to make it known.

So yeah, that’s what I’ve got for you at the moment. Thanks for checking out the site and reading my posts over these last 8 months or so. It’s been a lot of fun so far and I plan to keep writing in 2012 and longer assuming the world doesn’t end next December. Once my thesis is finally wrapped up I can even post on a more frequent basis too!

Happy New Year,

Carmen


Expanding the Analog Geek’s Toolkit

So I spent the other weekend in Washington, D.C. visiting a friend for his birthday. While I was waiting for my plane to take off in RDU Alan over at Tektronix was kind enough to provide me with some pre-flight entertainment. Back in 1987, Alan assembled The Ultimate Analog Engineer’s Toolkit designed to provide solace to engineers dealing with such problems as noise, the Miller Effect, and management, among other things. My personal favorites were the box of dBs (positive and negative flavors of course) and the Parasitic Pesticide. I tried to order some samples directly from Alan himself but he said his stock has run dry. I hope he can get another shipment delivered in time for the holiday season.

Anyways, as I was sitting in the terminal after reading it and I started to come up with a few additions to the toolkit and I present them to you here.

The Low Flow Current Adapter – We’re all familiar with the low flow shower heads installed in bathrooms nationwide to reduce water consumption. The Low Flow Current Adapter works in much the same way only on current instead of H2O. Plug this bad boy in between the power source and your circuit and watch as your product’s power consumption plummets before your very eyes.

Frequency Shaper Tool - Sometimes designs run over budget and when this happens you can’t always afford the box of high quality dBs needed to make a circuit meet the required specs placing a lot of “hertz” on you the designer. This is where the patented Frequency Shaper Tool comes in handy. While not as precise as a Box of dBs its low cost and reliable performance makes it ideal for the engineer on a budget. The Shaper allows a designer to grab a hold of an amplifier or filter’s frequency response and bend it to the desired shape. Need to nudge a zero in the stop band? Squeeze just a little more rolloff out of a filter? Reach for the Frequency Shaper and bend a transfer function into submission.

DocuGel – Come across an old PCB, product, or IC and have no idea what it does or how to use it? Did someone who’s clearly not as bright as you are forget to document their work and now the burden to upgrade the device is on you? Spread some DocuGel on the offending product and leave it sit overnight on your bench. Return the next morning and find datasheets, BOMs, gerber files, and schematics laying on your bench!

Grounding Stakes- Nasty PCB layout causing you problems? Is your circuit’s performance suffering at the hands of ground refusing to sit at 0V? Pound a ground stake into an open portion of your board and watch your problems disappear. Let your circuit know you only accept 0V, no more, no less.

I accept checks and all major credit cards :-)


Vintage Tek Gear

I was poking around in the Design Lab at work and happened to come across a few pieces of old Tek Gear. There’s one FG504 Function Generator and two AM503 Current Probe Amplifier modules together in a TM504 Power Supply chassis. The FG504 can generate a sine, square, or triangle waveform up to 30Vpp over an impressive 1mHz to 40MHz frequency range. It also has a host of other features too including burst and sweep modes. The AM503 can be attached to any oscilloscope and allows for current measurements of up to 100 A depending on the current probe used with it. I’m not sure if this stuff gets used much anymore, if at all, but it’s still cool none the less so I snapped a few pictures to share my findings. I also did a Google search for each module and found a few interesting sites which I linked to at the end. Enjoy!

Results of my Google searching:

  • What looks like a product page from a catalog for the function generator
  • Catalog page for the current probe amp. The AM501 Op Amp Module also on this page looks pretty cool too. I’d definitely like to play around with one of those.
  • An ebay page selling the power supply (includes pics of just the supply itself).
  • A manual for newer versions of the AM503 (AM503B and AM5030)
  • Website which shows a picture of the inside of the FG504, all through-hole and some crazy looking traces.

Want to see some more Vintage Tek Gear? Check out my new post on the 576 Curve Tracer.


Useful App Notes: Part 2

AN104 - Load Transient Response Testing for Voltage Regulators, Linear Tech

An app note written by the late great Jim Williams back in 2006 discussing how to test linear regulators by applying a load transient to the output. These techniques discussed are also directly applicable to switching regulators as well making the app note doubly useful. My favorite parts of this app note are Figures 6 and 8 which show two interesting transient generator circuits, one BJT based and the other FET based. At the moment I’m trying to gather up the necessary parts to prototype one of the circuits and possibly throw it in a project box to use at work. A great resource for anyone doing work in power electronics.

ANA – The Monolithic Operational Amplifier: A Tutorial Study, National Semi

Want a fantastic reference about the intricacies of op amp design? Look no further than this app note written by Bob Widlar. Covering everything from input/output stages, to techniques for increasing slew rate and proper layout, any and all relevant topics related to op amp design are discussed.  There’s even a section on thermal feedback which is interesting as it’s not a topic typically covered all to often. While I don’t think I would recommend this app note as a stand alone reference for a beginner, it’s perfect for someone looking to expand their knowledge on op amp design. If you are a beginner I would suggest pairing ANA with either Johns & Martin or Gray & Meyer. Fun Fact: Gray and Meyer are cited several times in the bibliography.

The Data Conversion Handbook – Analog Devices

Not exactly an app note but still another good reference to keep at hand. If you’re looking for a general overview of ADCs and DACs  along with a bunch of other useful information I highly recommend this book. Chapter 1 is an interesting history of converter technologies throughout the ages. Chapter 2 discusses sampling theory and defines converter specs. Chapter 3 covers the various topologies of DACs and ADCs from a primarily applications standpoint rather than a design one but is still incredibly detailed.  Chapters 6 and 7 cover interfacing and all the various support circuitry that goes into properly using converters in your design. Chapter 9 has a some good information regarding board layout, passive components, prototyping, and more. I read through most of this handbook two summers ago during an internship while waiting for automated tests to run and I can say I learned quite a bit.


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