Tag Archives: Tektronix

The home lab of Bo Lojek

I was touring Atmel’s fab in Colorado Springs, so I made a point of contacting Bo Lojek, the author of the great book, the History of Semiconductor Engineering. Although Bo is now a professor at University of Colorado, he worked at Atmel for 15 years. I was honored that he asked me to his home in Colorado Springs. Well, I have a pretty good home lab, but Bo’s lab just blew me away. Bo said he wanted to be an engineer from the time he was 7 years old. It runs in the family, his dad was an engineer too.

So Bo told me that he built his house in Colorado Springs. If one of my Silicon Valley buddies says this he means that he had a custom floor plan home built by a homebuilder. For Bo, it means he had an engineer design the house to his specs, using metal studs, and Bo himself constructed the house, driving all 37,000 self-tapping drywall screws. I think he said it was 3600 square feet. Yes, it’s an engineer’s paradise.

KONICA MINOLTA DIGITAL CAMERA This is what meets you at the foyer just inside the front door of Bo’s house. Bo said if I came back at daytime I could check out his collection of Dumont scopes in the garage.

KONICA MINOLTA DIGITAL CAMERA Every engineer worth his salt needs a Data General Eclipse computer in the hallway, just for data processing emergencies. Bo has arranged for all his stuff to go to the University of Colorado when he dies. It will be great to keep this museum together. It will also be a great excuse to visit Colorado Springs, other than to meet the space aliens that the Stargate people have inside the NORAD mountain.

KONICA MINOLTA DIGITAL CAMERA Bo has some early computer boards nicely framed on the wall.

KONICA MINOLTA DIGITAL CAMERA Lojek has a huge collection of voltmeters, including this Cubic model V-46A. It uses telephone stepper relays and a handful of transistors to measure voltage. Pretty cool for 1960.

KONICA MINOLTA DIGITAL CAMERA On Bo Lojek’s bookshelf are propped up some vacuum tube modules from a very early computer.

KONICA MINOLTA DIGITAL CAMERA And let’s enjoy Bo checking out the whole bookshelf. His house is not only engineer paradise, its college professor paradise.

KONICA MINOLTA DIGITAL CAMERA While Bo does not have the disorganization of dear departed Bob Pease, he does have a few things littering the floor. I used to use the same Data IO programmers to program the microcontrollers I designed into my consulting work.

KONICA MINOLTA DIGITAL CAMERA It does not disturb me that Lojek has a stack of early Tektronix mainframe scopes. What bothers me is I have several friends that have the same sort of stack.

KONICA MINOLTA DIGITAL CAMERA How about these early 2N1302 transistors from honored competitor Texas Instruments?

KONICA MINOLTA DIGITAL CAMERA Lojek has drawer after drawer full of electronic components, including these vacuum tube computer boards.

KONICA MINOLTA DIGITAL CAMERA Bo told me that when Bob Pease visited his house, he could not tear him away from these two analog computers. I should mention that I knew of Bo because Pease told me what a cool guy he was. Bob knew Bo because Bob edited Bo’s book. Since English is Bo’s second language that was a lot of work, but Pease was happy to do it since it was such an important contribution from such a cool guy.

KONICA MINOLTA DIGITAL CAMERA Here is a close-up of the analog computer that so entranced Bob Pease.

KONICA MINOLTA DIGITAL CAMERA All this cool stuff above is just stacked like cordwood all over the house. This is where we finally got to Bo Lojek’s lab bench.  Bo told me he likes to write or read for a while, but then he has to go to the bench to do some experimentation. It reminds me so much of my mentor Bob Pease, who had an equal love for working with his hands a soldering iron.

KONICA MINOLTA DIGITAL CAMERA Every surface in Bo Lojek’s house is a treasure trove of memorabilia and electronic equipment.

KONICA MINOLTA DIGITAL CAMERA Here is a very early computer board that used “air gap” integrated circuits. Analog Devices’ Barrie Gilbert told me that he got into electronics because surplus WWII magnetrons were so beautiful to look at he had to learn how they worked.

KONICA MINOLTA DIGITAL CAMERA And how about this, a Bob Widlar business card? I love the title “ROAD AGENT”. Widlar had style.

KONICA MINOLTA DIGITAL CAMERA And when your engineer friend tells you he has a walk-in closet— this is what he means.

KONICA MINOLTA DIGITAL CAMERA Lojek has an artistic streak. Amongst the pretty glass are a handful over very early galvanometers, some from the 1800s.

KONICA MINOLTA DIGITAL CAMERA More cool galvos and such. I wonder if the founder of Digi-Key has that same telegraph key? Ronald Stordahl started out Digi-Key by selling electronic telegraph key kits to Ham radio operators.

KONICA MINOLTA DIGITAL CAMERA Here Bo Lojek admires a framed set of Minuteman missile circuit boards. Jim Williams had an interconnected set on his living room. Check the Minuteman missile PCBs and Jim Williams out in this video.

KONICA MINOLTA DIGITAL CAMERA OK, so I lied. That picture earlier, the one I called Bo Lojek’s lab bench. That was just the emergency downstairs lab bench useful of quick jobs. Here is the real lab bench. Next time I get to his house, I will fire up that big soldering iron and put it down right before the picture, so there will be a wisp of smoke coming off of it, like a Cowboy’s 6-shooter.

KONICA MINOLTA DIGITAL CAMERA That main bench above has a side bench on another wall.

KONICA MINOLTA DIGITAL CAMERA And books, boy do college professors love books.

It was a real treat to see Bo. He said he is going to try and make it to the next Analog Aficionados party, so I will remind him so he can be among like-minded souls out here in Silicon Valley. The party will be Feb 8 2014, the Saturday before the IEEE ISSCC conference.

Precision resistors and tolerance stackup in general

This must be the season for great graphics. After seeing the solar cell output over temperature graph a couple days ago, today I see this great article about the reality of using precision resistors. It is from the great folks at Vishay, by way of my former co-workers at ECN Magazine.


Vishay shows what can happen to their beautiful resistors once you and your customers get your grubby hands on them. TCR means temperature coefficient of resistance.

The same chart got used in an article in EDN, where I worked. The graph also saw use in an Electronic Design article about foil and thin-film resistors. The mother lode was from a Vishay app note by Yuval Hernik.

If you are using a resistor to measure current you should not trivialize the accuracy problems that come with the real world. You can see in the chart that the ±0.05% resistor you buy from Vishay can end up being a ±1% resistor after a few years in the field. It’s not Vishay’s fault. They did not stress the resistor soldering into the board. They didn’t expose it to humidity and temperature gradients that damage the device. They didn’t drop it and shock it and over-voltage it.

The point of this is that you can’t build a product that specs ±0.05% accuracy if you start with ±0.05% resistors. You customers don’t care what you buy from Vishay and they don’t care what you built. They care about they use, perhaps years later, at some horrible temperate in some inhospitable humidity over some astronomical altitude. When I was at Analog Devices they had a test for voltage references that was running for years. Years! This was to evaluate the long-term drift that the parts would exhibit. I am happy to say that the ADI parts seemed better than most.

And here is the thing— when it comes to these drift problems, no one can tell you what is going on. We simply don’t understand the physics of it. I contend we really don’t understand noise either, but that is an argument for another day. But drift, which you can think of as “dc noise” if you want mess with your head, is a universal problem. We older folks that used to wait for tube radios to “warm up” seem more comfortable with the concept. But op-amps and maybe even discrete components have to settle in as well. This is not the few microseconds it takes for the internal circuits to start working. It is the minutes or days it takes for the amplifier to come to its final dc offset error.

I have several pals that are trying to make their own test equipment to save money or just build things like a Maker movement. That is fine if you don’t really have to trust it. Believe me, Fluke and Agilent and Tektronix earns every penny they ask you for. This is why I am wary of cheap knock-off test equipment. I would rather buy used name-brand equipment that I can trust to keep accurate over their lifetime.

As to these resistor tolerance issues, one answer is that you calibrate the product every time it’s turned on, or even more often. When I did automotive test equipment at HP (before Agilent split off) my solution was to use the best voltage reference that money can buy. Back then it was Thaler. Since then (1998) I found out that the Thaler part I used was a National Semiconductor part that was hand-selected by Thaler. No matter where you get it, you have to have a low-drift and low TC (temperature coefficient) part. I also used very good initial accuracy parts, since I did not want to have to calibrate the board the first time in the factory.

This way, I had the acquisition system measure its own reference. That way I could calibrate any errors or drift in the attenuator resistors. The other aspect was using a very good crystal. This way you know voltage and time. Most everything else you can derive in firmware. I called it “a rock and a ref,” since rock was slang for the quartz crystals. I still remember Bob Shaw asking me what pots had to be adjusted on the board for manufacturing. I told him there were no trim pots or trim capacitors. He was astonished. I told him about a rock and a ref. I joked that if he really wanted pots I could add them back in. He told me no, and thanked me for designing something that did not need factory calibration, since it just calibrated itself. The other horrible thing about pots is that they are terribly unreliable components. Only electrolytic and tantalum capacitors are worse. If you have vibration, pots are a really bad idea.

OK, product pitch time, these accuracy problems are why you should think about using Atmel AFE (analog front ends). We make them for the smart power meters. And I don’t mean to imply that Atmel is the only outfit. All the semiconductor makers make AFEs for various tasks. If it can offload your accuracy problems with calibration or the precise accuracy that comes with semiconductor processes, it is always a good deal to pay for an integrated solution rather than build it yourself. For years I told National Semi that people would pay for precise ratiometric resistors. It took Linear Technology to actually make the parts.

The May 2013 Silicon Valley eFlea electronic flea market

The Silicon Valley electronic flea market, dubbed the eFlea by my pal and long-time attendee Dave Ruigh is this Saturday, May 11, 2013. My buddies and I try to get the eFlea by 6:00AM. Then around 9:30 we go over to Bobbies breakfast bistro and compare purchases and catch up on the scuttlebutt. We are often still gabbing by 1:00PM. There is a 3-dollar parking fee at the eFlea—you have to get a ticket out of one of the machines or you get a real ticket for 35 bucks. If you want to sell it’s still only 20 dollars for two parking spaces inside the market.


Be sure to get to the eFlea at the crack of dawn if you want to scoop up the really good stuff. Many attendees carry powerful LED flashlights to help pierce the darkness.


Because I go to the eFlea with my totally cool pals, they tip me off about toally cool gear like these Blonder-Tongue units.


My EE buddies are always looking for test equipment. Here is a nice HP signal generator. That is why you used to see Jim Williams and Bob Pease at the eFlea. Bob Dobkin, the founder of Linear Tech is there most months, as is Dennis Monticelli from TI.


Here is a nice Tek scope. There are scads of test equipment every month. Hey, something has to compensate us for living in this over-priced hell-hole called California.


There is a fellow who deals Metcals and every other type of soldering equipment you can think of. The eFlea is where you get that 0.010 lead solder.


Ya can’t design it if ya can’t see it. All my pals have an assortment of visual acuity enhancers, everything from eye loupes to these zoom inspection microscopes.


And here is a modest selection of power tools.

Well, you get the idea and see why it’s a good thing to show up early. Next post I will talk about our breakfasts at Bobbies and the cool gizmos we find.