Uneasy Pease

From my bad interview at a no longer existing analog company along in 1993 along with a downturn in the economy I decided to focus my education in the California central valley and everything related to it.  (..."Please wait for the CEO he will see you next", that was after a long afternoon of technical interviews without even a snack break, with low blood sugar,  I responded "Don't bother", took off my badge and walked out the door and back into graduate school)  I had my electronics hobby kits, the recording studio work, automated laundry repair etc to deal with so I wasn't into Bob Pease and the analog scene being (heavily influenced) by National Semiconductor in the early 1990s.  I noticed in my visits to National that they had excellent analog designers and I will mention a few.  Its been flattering to hear feedback that my posts remind them of Bob's writings so I thought its time to "dig up" Bob. 

This posting is basically an old school book review of Bob's Kindle book on Troubleshooting analog circuits.   With practice my writing should get better and become more like Bob's.  But first more about Mr. Pease.

I recall a SSCRL (UCD Seminar) where we had a guest speaker Bob Pease (1994?).  A somewhat frail looking graying and bearded man with numerous cutout foils for the overhead projector.  His presentation was about a front-end of some kind I recall he was interactive and asked questions to the group as he went along.  In a mechanical fashion he would uncover paper to reveal new information in the overhead transparency.  (In the old days we had these projectors with this clear film...it was analog...)  His talk was pretty good, low-tech and down to earth entertaining.  Bob was an expert interacting with other engineers and there were more than a few laughs while he disarmed difficult to gather analog concepts.  His talk was second best unfortunately that year beat out by Rich Reay who gave out a six-pack for nailing the old common-emitter gain problem.

My next interaction with Bob was when I visited National Semiconductor as a scholarship award winner. Bob wanted to meet us it was important to everyone including Bob.  Funny I remember the museum they had in the building with old electronics that was really cool.  Glass cases with old shiny analog guys like me like that stuff.  The door gift for the awards was an analog clock.  I recall the clocks all lined up with their hands in different random times at the beginning of the event.  Then the clocks were passed around to me and the other award winners.  As we left on a tour a looked back in the room and all the clocks were correctly set.... engineers and OCD.  Then a couple years afterward there was my interview at NSC in 1998 where my visit to Bob required me to brave his "dual cubicle" and find him in the corner between stacks of papers.  He shook my hand, promptly reached into a corner and pulled out a poster of "Bob Pease Lord of the Bandgap" which he promptly signed and sent me on my way.  My friendly host Pat Tucci and the creative Sing Chin made for a good day of data converters and at least one display chip. My Bob Pease poster was donated to the Lab and I don't think it was unique.

Now some 16 years later I had a credit on Amazon so I purchased a rather expensive Kindle book "Troubleshooting Analog Circuits" by Robert A. Pease ISBN 0-7506-9949-8 c 1991 for $37.54 soft-copy.  You would think this would be an enjoyable read for many but this was my first exposure to Bob's writing and how his mind works.  His writing and reasoning are amazingly clear following a logical progression.  He comes to good conclusions with his solid understanding of the underlying physics of electronic devices.  When it comes down to it we electrical engineers just apply physics to make money for our employers. Bob's book can be summarized as observe, be aware and think. Seek out the physics as to "why".

The book is quite excellent including photos and clearly drawn schematics.  Some books don't look as clear in their Kindle form but this is an excellent conversion including the figures.  In the first chapter he covers cost oriented test equipment.  Good advice of course about getting the most accuracy out of meters.  Choose the right tool for the job its basic to Bob he was trying to do the best at bench analog. His test instruments are cheap and aimed more at low-frequency DC/DC converters and the like, its important to understand what Bob was working to get the most out of it.  It also helps if you have seen some of these old components before, you should know a 2N3055 in a TO-3 will leave a welt if it hit you on the head. A TO-220 has a screw tab on it, so on.

Bob covers passives in chapters 3 and 4 including noisy resistors, film, wire-wound with their smokey charred failure mechanisms.  (He didnt mention you can identify the bad component by the smell, so basically many analog gear-heads know what different parts smell like when they burn such as the fishy burnt aluminum electrolytic.) The inductor section actually hurt to read.  Yes the saturation current of an inductor decreases at temperature.  No, the inductor is not the same after you hammer it with current, that took me and a team of guys at least a week to figure that one out.  Bob could have saved me a weeks there and at least of lab pain.  (abused inductors can de-solder themselves)   Dried capacitors (seen that) bad electrolytics without bias, oil filled, anything with "ene" is high performance and tantalum caps suck for Q.  Type of capacitor dielectric hurt too (I know guys who have spent weeks debugging poor choice of dielectric in a DSL application) they could have benefit from these two chapters.  I think I could have saved a few gray hairs and months of debug over the years had I got this book earlier.  Bobs chapters here remind me of Henry Ott's book on Noise Reduction Techniques in Electronic Systems (1988 John Wiley ISBN 0-471-85068-3).

His section on board issues has a bit of the self inflicted in it.  Bob lived on the board, 3-d circuit design-fly wire.  Air is an excellent dielectric seems more of an excuse to stay with what works. This is the way he understood things. He wasn't into the SSA "the three views" (covered in a an earlier post) wherein the text-netlist can be hacked like his 3-D circuits.  Hacking the input simulator input netlist (ASCII) is akin to his 3D lab experiments but in a sterile environment.    This power would scare Bob for sure with his dislike of computers, however if he were to have leveraged his approach on the simulator who knows where we would be.  (No I am not saying bench work is obsolete.)  I my work I try to avoid situations where the physics is so sensitive that a single fingerprint or a misting of flux can wipe out the performance.  Physics will dictate exactly what your circuit does, always.  From a street-smart standpoint it sounds to me like it may be a good idea to integrate sensitive electronics since the package will protect the internal high-impedance nodes.  Put thermally sensitive stuff close together.  What matters to the customer most is the solution in the end.  Having circuit boards so sensitive makes me wonder about how robust board will be in the long run especially when you don't know what the customer is going to do with it.  I think of random environments such as a guy who travels frequently with the equipment to a smoggy desert, then a dry polar cap all along blowing cigar smoke at the installed board. Of course Bob would just put the board in the dishwasher that should clean off the smoke.  

He covers wearing out Zener diodes, how Zeners actually avalanch over 3V, ok following been there but key to understand.  (Michael Altmann taught me a few things about Zeners he may have learned from Bob before going back to Intel.) Bob next talks about finger debugging, the capacitance of a finger loading a circuit, yes fingers are useful in debugging and I have had my share of shocks and burns, still Bob keeps going down the practical debug path.  Even with a stocked lab Bob would use everything in his arsenal to debug.  The fuse section is excellent I think many of us don't know AC vs DC and fuse ratings this was good.  We have all seen transistors sacrifice themselves to protect a valuable fuse, not much on that in the book though but it seems like something Bob would write about.  Resistive diodes, blown bipolars and MOS we have all have seen our share of those.  The leaky 1N914 section was excellent while not a big surprise to hear about since I preferred the germanium diodes in crystal radios since the gave more volume than the 1N914.   Bob is an expert at DC DC converters (ironically my least-favorite circuits) having fixed numerous bad boards stuffed with non typical components required for typical designs.  He reminds me again and again of how I don't like those circuits (because often their failure can be catastrophic).  Its hard to debug a chip when you pour its innards out of the package into a heap of glass after a fail.  (no, it didn't melt-down when I was done with that circuit but the horror)  Some DC DC converter issues are audible but that part of my hearing was blown out long ago by stress testing audio power amplifiers with Led Zepplin, The Who and sonic holography experiments involving reproducing actual recordings of freight trains (the Mach 5 experiments~1990).  Bob doesn't mention audibles his hearing was worse than mine.

So in general if you have not read Bob's book I highly recommend it.  This is especially true for "non-hobby" types or people who have picked up their analog later in life.  The years have changed analog and those old exposed connections are now buried inside some little device or surface mount pc board.  We in the industry have been working hard to make sure new hobby guys find analog as intimidating as possible with microscopic difficult to deal with components.  If this is your first exposure to practical electronics is the university you should rush to by Bob's book, although it does show some age.  One thing to consider is that the knowledge in the book is decades of experience so the $37 for a Kindle but is a steal! (I sadly estimate Bob's book could have saved me 100s of hours.  Some hours, in a crunch time for example, you can never get back!)

Reading Bob's book made me wonder how relevant it will be another 10 years from now.  Its doing very well by the way as the entire industry is changing.  (Physics doesn't change fortunately).  We are trying to get the human out of the system as much as possible since we are imperfect, make cold solder joints occasionally and miss a color code multiplier.  Bob's techniques of circuit analysis and phase margin checking are useful but few people now build up something without simulating it first.  Do not let that the simulator think for you but help you think.  You can still ponder what is going on and why the result may or may not be accurate.  In fact its critical you do so.  Do I believe the result?  That is a key reason why we go to school and learn physics and engineering.  Those people who work along side me know I distrust new tools and flow without independent verification.   I hate tool and software changes.  Bob had it correct that simulators can impair circuit thinking if abused.  Simulations are garbage without thought.  If anyone from Cadence is reading this please allow us to purchase a release with only bugfixes and NO new features to break and or screw up other working features.  We are not allowed to re-compile our multi-million dollar masks its hardware.

Personally I am a big fan of the simulator since when driven by an expert it can enhance understanding.  We take it for granted that we can look at any signal in the simulator and get a waveform representing what is happening at that spot with respect to time.  After working on a circuit the designer gets an expectation of what to see at various points.  After a while, this gets committed to memory and we can be "surprised" when we don't see an expected result we understand.  After years of staring at simulator outputs and anticipating results I can now see waveforms in my mind.  (My internal transient simulator I call it I am not unique in this ability since many of us have it).  I can debug circuit problems anywhere even while driving or on a cross country flight.  Often I have a parameter sheet from the process so I can do hand calculations.  For me as a simulator all I need is rest, a good meal and time to focus.  The biggest challenge is the latter.

Using Bob's analog "3D cloud of circuits" approach on the bench is akin to an expert hacking on a netlist input to an analog simulator.  At this point in my career I can visualize a smaller circuit in my mind and write an HSPICE deck off the cuff to simulate it.   There is an added advantage here with a simulator since the elements are ideal, don't require soldering and infinite component values are available.  This sounds harder than what Bob due to the open ended flexibility but it all depends on your perspective.  I am not alone in this ability visualize circuit netlists as circuis and most good people I know debug or track down issues in an any of the three views.  In simulators tolerances can be checked in sim cases, voltage sources are perfect as are current sources, volt-meters have no load at all.  If desired, devices can be matched perfectly.  All connections are perfect in a simulator making soldering skill a moot point. You can quickly and perfectly connect any two or more nets with a few lines in a SPICE deck.

In an enlightening section in the second half of his book Bob demonstrates how difficult a reliable test-board can be to produce.  I take this as a challenge as an engineer to make the final product as insensitive as possible to external elements (within reason).  Bob has some good points but if you can pull sensitive components inside the chip there is much to be gained in terms of resistance to handling.  If the passive device is not present it can't mess up or go bad.

The scale of electronics is changing.  The discrete components are expensive for our customers and take up valuable board space.  Complicated circuits (such as a calibrated ADC) cannot be hacked together on the bench easily.  The simulator has its purpose.  Bob's book is still useful today because the physics of the analog situation has not changed.  As long as the physics remains so will Bob's book.  Buy it, Read it, Live it!


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SSA Announcements:

Saturday 1/25/2014 San Francisco Yacht Club
UC Davis Engineering Awards on January 25th in San Francisco where Stephen will accept his teaching award.

February 2/9/2014 through 2/12/2014 ISSCC 2014 San Francisco
I will be attending the ISSCC 2014 in San Francisco from 2/9 through 2/12.  I will be staying at the hotel.

-Ken