What approach should be used when solving a circuit?

[yungman]

Well I might be one you'd show the door too. And knowing what I know, I wouldn't be sorry about it. I'd likely ask the beta to determine if it's necessary to improve the voltage divider bias as you describe. Your management style would attract fly by the seat of their pants type folks in my opinion. Lowering the voltage divider resistance also draws more power. Would you show me the door if I asked if this circuit went into a product that is powered by battery? Concerned about battery life and all. You want an engineer who is actually able to make the best set of compromises or one that simply gives you answers that make you feel good?

There's FETs.

That was a test question. The idea is you use common sense approach, not just analyze. I had very good luck in hiring people.

 

[Averagesupernova]

Of course there are FETs. Or any other of hundreds of ways to accomplish something. I find your approach is silly. Ask an open ended question, expect an open ended answer.

 

[berkeman]

It has been suggested that the EE interview posts be broken out of this thread into a separate thread. What do folks think?

 

[jedishrfu]

I would put a lot of money on it, that interviews for entry-level candidates are very different from people who have more than 10 years of experience. Almost all of my interviews did involve setting up equations and using fundamentals.

No kidding unless you get a stupid interviewer. I once nterviewed for a senior level position at a startup and got asked how to swap two variables. To be fair he was a junior programmer who didnt know how to interview.

Also interview questions don't tepresent the job either but are given to see how you react under pressure, how confident you are and sometimes how creative out of the box you are. It always good to collect names of interviewers for thank yous and more importantly interview them about the job working environment and anything else you can think of. Try to build a connection.

On another interview, i got asked a trick C++ question and before answering I asked the interviewer if he read Dr Dobbs. I answered it and then countered with one frim the Dr Dobbs article on the top ten C++ interview questions and he couldn't answer it so I gave him the answer.

I turned the job down because they wanted me to fill a project mgmt position, promising to transition me to development. Bottomline, don’t fall for the promised switcheroo and negotiate your salary as leaving one job to go to the next often means a loss of vacation time and other intangibles.

 

[Joshy]

I think a thread related to interviews may be of high interest (it is to me) and there are a few interesting perspectives buried in this thread, which really should have been more about approaches to solving problems or analysis. I think it got mixed up because of course we're asked technical questions during the interview.

 

[yungman]

I used to give the test like in post #25 to technicians. These are something I learned in Heald college for AA degree. The book is by Malvino. I thought people should be able to answer easily even if they only gone through AA degree...WRONG. Then I put these type of question for engineer and thought this is only to eliminate the fake ones....WRONG! You'd be surprised how few can answer those.

I NEVER had a formal EE education. My major was Biochem for under grad. Electronics was and IS my passion and hobby. I completely self studied. I went through Heald in 1979 and got my AA in electronics in 9 months. I never even had the class on analog, I just read the Malvino book. Then change to different jobs to learn different facet of electronics like with LeCroy to design data acquision, Exar to design IC, Seimens to design Utrasound medical scanners etc. I expect people that went through the analog class would find it a breeze to answer those questions! I studied back ALL the undergrad EE and beyond....Like Electromagnetics, calculus like Differential Eq and Partial Diff Eq in order to study EM and RF. I thought people that went through college will have no problem with these...AGAIN...NOT...What are they teaching in college? All I was looking for was someone with common sense problem solving ability.

I had a job interview in 2002 with the same type of question...as Sr. EE. I got hired, we talked later, we were laughing how these kind of simple question can trip up those experienced EE.

 

[Averagesupernova]

All I was looking for was someone with common sense problem solving ability.

That ability in my opinion is more part of a person's core personality. It has little to do with what is taught in schools. School may unlock what a student didn't know they had when it comes to that ability but I think that's an exception.

 

[yungman]

That ability in my opinion is more part of a person's core personality. It has little to do with what is taught in schools. School may unlock what a student didn't know they had when it comes to that ability but I think that's an exception.

You've read my questions in post #25? It's very simple. How can it trip up so many people? These are real life circuit one encounters in analog designs. These questions are straight out of this book which I had to 1979 version. This was used in Heald College ( a technical 2 years AA degree for technicians). :
https://www.amazon.com/s?k=malvino+electronic+principles&crid=OHW65HC5U21O&sprefix=malvino,aps,351&ref=nb_sb_ss_i_3_7&tag=pfamazon01-20

I don't know how we end up talking about interviews. The original question is about "how to analyze...KVL...". In my view and from my experience specialized in analog, RF, mixed signal designs, I never ever use all the network theorems like Thevenin's Theorem, KVL and all those. Just look at the circuit, make it simple like in my two questions so the voltages in every point is very obvious with V=IR.

If I really want to go deep, I rather looking at the real circuit, how the ground return current run around on the ground plane, how to avoid ground loops that generate EMI. You really want to talk deep circuit theory, this is deep. And this is really really important in real world. That's what I was contracted to KLA Tenco in 2002 to help them on the layout of their few Giga pixels CCD circuits( when the commercial camera was only about 6M pixels). In school, the ground return is just a triangle and magically return the current. In real life, this is the major issue in circuit design. You get that right, the circuit is as simple as in the drawings in the textbook.

And in RF circuits, Smith Chart impedance matching. Yes, I was actually tested when I applied to Maxim in 2003. Too bad it took them like 3 months before they decided to make me an offer, that I long found another job already. The guy told me to hold on, the offer would come soon and he was angry when I said I got a job already! That was to design the reference circuits for their cell phone chip set, that involves designing matching circuits for their power circuits.

 

[yungman]

Want to get important knowledge in EE world, take a look at this book. It is quite easy, it has a way to explain grounding, ground current, EMI etc. in a very simple way with minimal electromagnetic theory. THIS is what is really important on the job.
https://www.amazon.com/dp/0133957241/?tag=pfamazon01-20

In today's high speed mixed signal environment, ADC, DAC, USB, 802.xx type of designs, knowledge of this is a MUST. You don't have to go into RF world to need this. Even if you are not planning to work as signal integrity engineer, you need this to design circuits and layout pcb. DON'T even think of depending on pcb layout designer to help you on this. It's on you to make the circuit work.

I don't even know whether people even hire pcb designers now a days, my last contract work I did a few years ago, we all design our own pcb. Good thing is I did my contract at home, barely went to the office once a week for an hour or so. To pass CE or UL, you better know signal integrity to pass those tests.

 

[jasonRF]

I've seen people from UC Berkley and Standford, they just so hung up with useless things, I would fired them if they were under me. RESULTS.

That's the problem, so many people studied and get good in all the formulas, but they don't have what it takes to design, getting the job done. That's the one I want to eliminate. Believe me, there are plenty of those people. Some people just don't have it, I just want to find people that have it.

Hi yungman,

Our paths haven't crossed for a number of years now - it is good to hear from you!

Clearly you worked at companies that expected new-hires right out of college to hit the ground running on circuit design. If there was a sufficient supply of candidates that met your requirements then it is easy to understand why you hired that way.

While I understand why you didn't hire those people, I think you are being pretty harsh by assuming that "they don't have what it takes", when in reality they may never have been taught to think about circuits this way and never read the kind of book that you mentioned reading to learn this stuff. This is really a failing of the EE curriculum. I know in my EE program there were only two courses in analog circuits and electronics that were required, and I don't recall either teaching this kind of thinking (or if they did, I just don't have what it takes ) . Instead, they taught basic semiconductor physics and attempted to give an intuitive understanding about how things worked at the device-level, and then moved on to hybrid-pi models and kvl/kcl... I think learning the intuitive understanding of circuits would have been a better choice, and I recall my advisor complaining about the way those courses were taught. Perhaps the upper-division courses on analog circuit design imparted this way of thinking, but I never took those courses. I was too busy taking extra courses on electromagnetics, microwave engineering, antennas, radar, physics and math. Today I can answer your transistor question only because a decade ago I got into hobby electronics for a short period of time; the op-amp question is something I could have answered by the end of my sophomore year.

By the way, I looked at Stanford's program and according to their web-site their EE program requires only one class each in analog and digital circuits
https://exploredegrees.stanford.edu/schoolofengineering/#majorstext
Of course they can take more if they want, but it is not required unless they pick particular specializations. The school I went to now has similar requirements as Stanford. These kinds of programs can be great at preparing students for graduate school and give students a lot of flexibility to prepare for a wide variety of careers. But some students (like me, and the ones you interviewed) don't leave with strong electronics skills - some because they didn't take the extra classes and some because they are better suited to other fields. On the other hand, there are a number of EE programs that require students to take several years of electronics classes; I suspect you had better luck hiring from those schools. I randomly picked Cal Poly to google and see that their well-regarded program is an example that fits in that category
https://ee.calpoly.edu/academics/undergraduate-program

cheers,

Jason

 

[berkeman]

Want to get important knowledge in EE world, take a look at this book. It is quite easy, it has a way to explain grounding, ground current, EMI etc. in a very simple way with minimal electromagnetic theory. THIS is what is really important on the job.
https://www.amazon.com/High-Speed-D...x=signal+int,aps,256&sr=8-3&tag=pfamazon01-20

I know that book quite well. Howie Johnson was one of the first engineers to work at the startup that I joined many years ago (now public and acquired several times by larger companies). After helping the startup to get going, he moved on and published that book (I believe he also wrote a regular column for EDN or some other big EE periodical). When he published his book, our VP of Engineering bought copies of the book for all of the engineers at the company, so we all ended up with it on our bookshelves. I did a lot of work in EMI and RF, so I referred to his book fairly often. It's one of the few books that I've kept over the years.

Small world!

 

[yungman]

I know that book quite well. Howie Johnson was one of the first engineers to work at the startup that I joined many years ago (now public and acquired several times by larger companies). After helping the startup to get going, he moved on and published that book (I believe he also wrote a regular column for EDN or some other big EE periodical). When he published his book, our VP of Engineering bought copies of the book for all of the engineers at the company, so we all ended up with it on our bookshelves. I did a lot of work in EMI and RF, so I referred to his book fairly often. It's one of the few books that I've kept over the years.

Small world!

This is actually about the most important knowledge an EE need to have in this mixed signal world. I don't think it's realistic to say "I just want to design digital or analog" in the industry. Everything is mixed, high frequency analog mixed with high speed digital circuit coexist in a tiny area of the pcb.

In 2000, when I was working for a small startup company, they actually had a specialist come in for 2 days to teach signal integrity. That's the first time I even heard of it. I was so into that, out of 6 EE, I was the only one that interact with the teacher while the other were kind of quiet...like dosing off. It was funny when I told my co-workers I really enjoy this, they said " you can have it all!". It's amazing I can predict how the current on the ground plane flows, that I can control them the way I want it.

Howard Johnson book is very good and easy. It's very common sense, minimal EM knowledge required even though it is related. Even though it's tittle is about digital, it's every bit applicable to analog design as antanna works both ways, the better it can transmit also mean the better it is to receive.

I still think EMI and RF is the most challenging and most fun area to work on. It's a totally different world. Not only you need a lot of knowledge, you need good pcb layout skill. I really enjoy pcb layout, that's where the magic happens. Now this is getting deep into electronics, very deep. To me, the most fun part is design with all distributed element using only microstrip to create capacitors, inductors but dancing around the Smith Chart. That the final pcb looks like a maze with pattern of copper.

 

[yungman]

Hi yungman,

Our paths haven't crossed for a number of years now - it is good to hear from you!

Clearly you worked at companies that expected new-hires right out of college to hit the ground running on circuit design. If there was a sufficient supply of candidates that met your requirements then it is easy to understand why you hired that way.

While I understand why you didn't hire those people, I think you are being pretty harsh by assuming that "they don't have what it takes", when in reality they may never have been taught to think about circuits this way and never read the kind of book that you mentioned reading to learn this stuff. This is really a failing of the EE curriculum. I know in my EE program there were only two courses in analog circuits and electronics that were required, and I don't recall either teaching this kind of thinking (or if they did, I just don't have what it takes ) . Instead, they taught basic semiconductor physics and attempted to give an intuitive understanding about how things worked at the device-level, and then moved on to hybrid-pi models and kvl/kcl... I think learning the intuitive understanding of circuits would have been a better choice, and I recall my advisor complaining about the way those courses were taught. Perhaps the upper-division courses on analog circuit design imparted this way of thinking, but I never took those courses. I was too busy taking extra courses on electromagnetics, microwave engineering, antennas, radar, physics and math. Today I can answer your transistor question only because a decade ago I got into hobby electronics for a short period of time; the op-amp question is something I could have answered by the end of my sophomore year.

By the way, I looked at Stanford's program and according to their web-site their EE program requires only one class each in analog and digital circuits
https://exploredegrees.stanford.edu/schoolofengineering/#majorstext
Of course they can take more if they want, but it is not required unless they pick particular specializations. The school I went to now has similar requirements as Stanford. These kinds of programs can be great at preparing students for graduate school and give students a lot of flexibility to prepare for a wide variety of careers. But some students (like me, and the ones you interviewed) don't leave with strong electronics skills - some because they didn't take the extra classes and some because they are better suited to other fields. On the other hand, there are a number of EE programs that require students to take several years of electronics classes; I suspect you had better luck hiring from those schools. I randomly picked Cal Poly to google and see that their well-regarded program is an example that fits in that category
https://ee.calpoly.edu/academics/undergraduate-program

cheers,

Jason

I have been away doing my own things for a few years. I was here when I was studying PDE and EM for the fun of it. I have been designing high end hifi power amps for a few years, I think I have hit the ceiling on that, so I start to pick up programming C++ and I am back here asking questions on that. It's just my crossword puzzle for old age to keep my mind from turning into jello! just keep learning from one thing to another.

I am absolutely surprised what you said about college EE major requirements. Only two classes of analog! I used to wonder what I missed not having an EE degree as my degree was biochem. Now I am grateful I did NOT take EE as my major! All these years, it's like learn when I need it. I kept changing jobs to different facet and study along the way to gain knowledge. From working for LeCroy designing ADC modules ( like digital scope), the Exar designing analog IC, to Seimens designing ultrasound imaging machine then to mass spectrometers then RF communication. Just kept changing fields and study along the way. So I just look at what is needed in the jobs.

What are they studying in the 4 years? All digital, embedded, firmware, FPGA etc.? In today's high speed mixed signal world, these are just part of the knowledge. Without high speed analog design, you won't go too far with just digital knowledge.

Semiconductor physics is good, but in my IC design job, I learned it from the older edition of this in 1984:
https://www.amazon.com/dp/8126521481/?tag=pfamazon01-20
It had a lot of circuit design, current mirror, differential pairs and all that. Anyone that took a course in semiconductor design should have plenty of circuit experience. I have to say, even in designing analog IC, I did not use those semiconductor physics, it's just "good to know". Actually design was just like normal circuit, you just use the available transistors, their limits. Using their resistors and get matching by layout etc. To me, it's just design with different available parts from discrete circuits. But of cause, I am talking about 30+ years ago, things might have been changed.

Yeh, I might be a little harsh, but the world is not like in college. I am sure now is good time as jobs are plenty. But believe me, I've seen market flipped around a few times. In good times, you have a pulse, you'll be hired. But in bad times, believe me, it is harsh. If you ever look for jobs between 2001 to 2005, you know what I mean. I had one interview on RF engineer position. I went two interviews, I got 100% on their test, that was on Smith Charts matching and all. I did NOT get the job because they said they need someone with more experience. That was harsh. My point is to make students marketable by learning the right thing even though it might sound harsh.

I worked for more than one startup companies, you get hired...and FIRED just as fast. I've seen people come and go in a month. That's harsh.

 

[Averagesupernova]

@yungman I really respect your high expectations. I feel as if in the past I have nearly forgotten that some of the formal laws in electronics exist such as KCL and KVL. It hit me one day when a coworker who troubleshot test equipment as I did asked me how I 'did it'. Apparently they thought I had some special magical view into what I was working on that they did not. Since this was a good friend I took a long time to give an answer that I thought accurately describes my approach at troubleshooting. What I learned by analyzing myself was that I was doing a lot of things that I was taking for granted. As a comparison, it was like describing every last little muscle movement involved in walking to someone who is learning to walk. I had no idea I was doing all of these things without thinking about it. You know why that happens? Practice practice practice practice. The only reason I may have been more special was because I probably enjoyed it more than anyone else I knew at the time.
-
So just because you think you aren't doing what someone less experienced than yourself does, doesn't mean it's true. You just aren't thinking about it.
-
And yes I looked at the circuits you posted. Simple stuff to anyone with experience.

 

[Joshy]

I can't do that op-amp one in my head :( I thought it was obvious, but then I noticed the resistors weren't balanced and I can't remember the formula by heart anymore.

 

[Averagesupernova]

I can't do that op-amp one in my head :( I thought it was obvious, but then I noticed the resistors weren't balanced and I can't remember the formula by heart anymore.

Don't feel bad. I had to go through it a couple times because my memory isn't what it used to be. Had to double check what the voltage was at the non inverting input. I'm not so slow as to look at the three volt source and not realize that the voltage on + should be -1 volt. But when I work through the other side I forget that I started with -1 volt. Probably just a sign of getting old.

 

[yungman]

@yungman I really respect your high expectations. I feel as if in the past I have nearly forgotten that some of the formal laws in electronics exist such as KCL and KVL. It hit me one day when a coworker who troubleshot test equipment as I did asked me how I 'did it'. Apparently they thought I had some special magical view into what I was working on that they did not. Since this was a good friend I took a long time to give an answer that I thought accurately describes my approach at troubleshooting. What I learned by analyzing myself was that I was doing a lot of things that I was taking for granted. As a comparison, it was like describing every last little muscle movement involved in walking to someone who is learning to walk. I had no idea I was doing all of these things without thinking about it. You know why that happens? Practice practice practice practice. The only reason I may have been more special was because I probably enjoyed it more than anyone else I knew at the time.
-
So just because you think you aren't doing what someone less experienced than yourself does, doesn't mean it's true. You just aren't thinking about it.
-
And yes I looked at the circuits you posted. Simple stuff to anyone with experience.

Actually I learn this in my very first 6 months I decided to learn electronics from the book by Malvino that is for technicians. It's just a practical approach in electronic circuits. That was even before I got my first real electronics job as a technician. I was a field service tech right before that and I discovered electronics was/is my ultimate passion. I studied this in between service calls in the car. I studied so hard I screwed up my job and got fired! I stayed home and studied 18 hours a day and got my real electronics job in 3 months. I thought this is as basic as it gets.

https://www.amazon.com/s?k=malvino+...,aps,223&ref=nb_sb_ss_i_3_7&tag=pfamazon01-20

 

[yungman]

I can't do that op-amp one in my head :( I thought it was obvious, but then I noticed the resistors weren't balanced and I can't remember the formula by heart anymore.

Think about the characteristics of an opamp:
1) input is very high impedance and will follow any voltage within the +/- supply voltage...say +/- 15V.
2) The output is open loop gain Av X (differential input voltage). That the Av is very high. Meaning the output will do everything within about +/- 13V ( need a little headroom from +/-15V) to make the differential voltage = 0.
3) closed loop gain of opamp is feedback resistor divide by input resistor which is 2K/1K=2
4) The DC voltage of the signal generator before the signal starts is 0V as drawn.

Arming with these, look at the circuit, the +ve input is driven by 1K and 2K resistor from ground to -3V. The voltage at +ve input is -1V as per (1) above.

Then let's assume from very start, output voltage is 0V. The generator output is 0V, so the voltage at -ve input is 0V. This means the differential voltage (+ve input minus -ve input) = -3-0 = -3V.

From (2) where Av is very high, the output will swing low. When it swing to -3V, the -ve input will be at -1V. At this time, the differential input = -3V -(-3V) =0V. So the output will stop going further down and stay at -3V. This is the resting point of the circuit or the DC analysis of the circuit.

When the generator start giving a triangular wave form, you can calculate that...BUT it is too tedious. That's the reason I ask only to draw the output waveform. You know triangular wave forms has straight slanted line, so you just have to find the two points at the tip and draw straight line. From (3), you know the gain of the circuit is 2. input waveform is 0.5V PEAK. you know the peak output is +/-1V around -3V(base line). So the output is swinging from (-3V+(-1V) to (-3V+1V) = -4V to -2V.

Last thing, remember, the signal generator is driving the -ve input, so the output waveform is OPPOSITE to the input waveform.

Most important thing is to remember the first two characteristics of opamp, forget about all the offset, frequency response and others first. Just the basic characteristics.

That Malvino book is very good. Believe it or not, I designed IC with not much more than this book. The Grey & meyer book just add to it, but I pretty much relied on Malvino for all the work.

 

[yungman]

Same thing for the transistor circuit.
1) assume Vbe=0.7V.
2) Since I did not specify transistor, just assume Beta is high. Meaning Ib=0 and Ie = Ic.Based on these two. We first find the voltage at the base which is voltage divider of 20K and 10K across +/-15V. Which gives -5V.

The voltage on the emitter of the first transistor is therefore V3 = -5.7V ( just 1Vbe drop from -5V)

The current through the 100+900 ohm is therefore I1 = 9.3V/1K = 9.3mA.

From (2), we know Ic = Ie, this means I2 = 9.3mA.

V2= 15V- (500ohm X 0.0093A) = 10.35V.

V4 is 0.7V lower than V2 = 10.35-0.7 = 9.65V.

With 9.3mA, r'e of transistor is about 26ohm/9.3 which is about 3ohm. We can assume to be 0ohm.

Gain of the stage is 500ohm/100ohm = 5. But remember the gain is inverted, so the gain is -5. This should be good to about 5% or so which in this case, is good enough.

 

[jasonRF]

I am absolutely surprised what you said about college EE major requirements. Only two classes of analog! I used to wonder what I missed not having an EE degree as my degree was biochem. Now I am grateful I did NOT take EE as my major! All these years, it's like learn when I need it. I kept changing jobs to different facet and study along the way to gain knowledge. From working for LeCroy designing ADC modules ( like digital scope), the Exar designing analog IC, to Seimens designing ultrasound imaging machine then to mass spectrometers then RF communication. Just kept changing fields and study along the way. So I just look at what is needed in the jobs.

What are they studying in the 4 years? All digital, embedded, firmware, FPGA etc.? In today's high speed mixed signal world, these are just part of the knowledge. Without high speed analog design, you won't go too far with just digital knowledge.
Semiconductor physics is good, but in my IC design job, I learned it from the older edition of this in 1984:
https://www.amazon.com/dp/8126521481/?tag=pfamazon01-20
It had a lot of circuit design, current mirror, differential pairs and all that. Anyone that took a course in semiconductor design should have plenty of circuit experience. I have to say, even in designing analog IC, I did not use those semiconductor physics, it's just "good to know". Actually design was just like normal circuit, you just use the available transistors, their limits. Using their resistors and get matching by layout etc. To me, it's just design with different available parts from discrete circuits. But of cause, I am talking about 30+ years ago, things might have been changed.

Note that many EE departments do require many analog courses to graduate (look at Cal Poly's curriculum, for example)- I was just pointing out that Stanford (which you had specifically complained about) did not require many. They do offer a number of electives in electronics, though, and their program provides students with many electives to decide for themselves what kind of degree they want. The program I went through was similar - and the next analog course I didn't take used Grey and Meyer for the text. Perhaps I would have understood electronics if I had taken that class. You might shake your head to learn that the Gray and Meyer course had a corequisite that mostly covered device physics, and the pre-requisites for both courses included an upper-division course in quantum and solid-state physics.

What did we study in 4 years? Well, some students did indeed take a bunch of analog courses. But some specialized in signal processing and communications, others in lasers/optics/quantum electronics, others in computer engineering/software/firmware, etc. As I mentioned earlier, I took a number of electives in electromagnetics, microwaves, antennas, radar, math and physics. The department explicitly told us that their goal was to prepare us for graduate school, and at least in my case they succeeded. I knew quite a few students who went on to top grad schools, but it probably wasn't the best program for some folks that were more interested in practice than theory.

To be honest, I chose to major in EE because I had fallen in love with electromagnetic theory by the time we had to declare and the end of our sophomore year. I had already taken the intro digital and intro circuits classes, and figured I could tolerate one more course on analog electronics if it meant I could take all of the fun applied E&M courses. If the department had required a ton of electronics courses I would have chosen the engineering physics major instead. Today I find circuits more interesting than I did as a young man.

jasonRF

 

[yungman]

Note that many EE departments do require many analog courses to graduate (look at Cal Poly's curriculum, for example)- I was just pointing out that Stanford (which you had specifically complained about) did not require many. They do offer a number of electives in electronics, though, and their program provides students with many electives to decide for themselves what kind of degree they want. The program I went through was similar - and the next analog course I didn't take used Grey and Meyer for the text. Perhaps I would have understood electronics if I had taken that class. You might shake your head to learn that the Gray and Meyer course had a corequisite that mostly covered device physics, and the pre-requisites for both courses included an upper-division course in quantum and solid-state physics.

What did we study in 4 years? Well, some students did indeed take a bunch of analog courses. But some specialized in signal processing and communications, others in lasers/optics/quantum electronics, others in computer engineering/software/firmware, etc. As I mentioned earlier, I took a number of electives in electromagnetics, microwaves, antennas, radar, math and physics. The department explicitly told us that their goal was to prepare us for graduate school, and at least in my case they succeeded. I knew quite a few students who went on to top grad schools, but it probably wasn't the best program for some folks that were more interested in practice than theory.

To be honest, I chose to major in EE because I had fallen in love with electromagnetic theory by the time we had to declare and the end of our sophomore year. I had already taken the intro digital and intro circuits classes, and figured I could tolerate one more course on analog electronics if it meant I could take all of the fun applied E&M courses. If the department had required a ton of electronics courses I would have chosen the engineering physics major instead. Today I find circuits more interesting than I did as a young man.

jasonRF

RF/EM was my ultimate passion, sadly I was too old when I studied them. I studied RF and microwave first starting in 2000. I used this book as my main book:
https://www.amazon.com/RF-Circuit-Design-Theory-Applications/dp/0130953237/ref=sr_1_2?crid=15X01H109J25B&dchild=1&keywords=rf+circuit+design+ludwig&qid=1596165099&sprefix=rf+circuit+design+l,aps,218&sr=8-2&tag=pfamazon01-20
with this as second book:
https://www.amazon.com/dp/0471448788/?tag=pfamazon01-20
I have others RF books also as supplements. I've been to Standford bookstore. I have more RF, couple lines type of books than their bookstore! I managed to do all the Smith Chart, distribute elements designs without studying EM( remember, I did not go to school).

Actually after I retired in 2005, I decided to study back my long wish of Electromagnetics. But I still have to studied through all the multi-variables, ODE. I actually spent almost 2 years away from electronics studying these. Then I went wild and actually studied PDE using the older version of this
https://www.amazon.com/Partial-Differential-Equations-Boundary-Problems/dp/0486807371/ref=sr_1_2?crid=320DZW9WLCL2E&dchild=1&keywords=partial+differential+equations+asmar&qid=1596165555&sprefix=partial+differential+equations+as,aps,210&sr=8-2&tag=pfamazon01-20

Then I felt I was ready for EM. I used this as my main book that I spent a year or two on as main book:
https://www.amazon.com/Field-Wave-Electromagnetics-David-Cheng/dp/0201128195/ref=sr_1_fkmr3_1?crid=39YVMT9KRBFZJ&dchild=1&keywords=field+and+wave+electromagnetics,+second+edition,+by+david+k.+cheng&qid=1596165683&sprefix=fields+and+waves+electromagnetics+cheng,aps,229&sr=8-1-fkmr3&tag=pfamazon01-20
I first actually communicated with the professor in San Jose State and he was kind enough to give me the problems and answer for his class using this book, but it's too simple, so I followed Cheng's book. But I worked out more of the assignments of SJ State.
https://www.amazon.com/Fundamentals-Applied-Electromagnetics-Fawwaz-Ulaby/dp/0132413264/ref=sr_1_3?crid=18WVWA2HNBJPD&dchild=1&keywords=ulaby+electromagnetics&qid=1596165844&sprefix=electromagnetic+ulaby,aps,223&sr=8-3&tag=pfamazon01-20

After that, I jump into Antanna design using this as my first book:
https://www.amazon.com/Antenna-Theory-Analysis-Design-3rd/dp/047166782X/ref=sr_1_2?crid=16RGSLRET3K1V&dchild=1&keywords=antenna+theory+balanis&qid=1596166013&sprefix=antenna+theory+balanis,aps,219&sr=8-2&tag=pfamazon01-20

Sadly, age catching up with me. I found myself forgetting what I learned just few weeks ago. I kept very good notes, so many times I read back my notes, I said "did I write all these?!". I read through the notes, it's all there, I did understand the material, it was good notes! At that point of time, I was quite burnt out and more important thing is...For what?! I have no intention to go back to work, why spent hours a day studying these! It's the hardest thing I study in my life particular self study.....Then forgot about it! Finally I quit in 2013 and move onto designing first guitar amps and then hifi power amps. They of cause a lot easier, I treat it as crossword puzzle like other seniors. Today, I am learning C++ in the other part of the Physics forums. No offense, it's a WHOLE LOT EASIER, those firmware, FPGA, microcontrollers are so much easier. I had no choice in my career to design a lot of those as we were mixed signal and I was the only one in the company to do that. I hope I can keep learn and learn to the day I drop!

 

[Joshy]

I do want to share what my interviews look like (as a candidate) normally for RF engineering positions. I'm still considered entry-level approaching mid-level with a little over 2 years of experience. Most of the interviews I've had are 6-8 hours long and I'll be interviewed by 4-8 people usually each one will have 1 to 1 although I've had groups of 2-3 people. Maybe it'll help someone else.

I am almost always asked to graph the step response of a RC circuit. I've been asked a few times to do it for a LC circuit.

I am almost always asked op-amp questions. Sometimes I'll be asked for all the different configurations including active filters, integrators, and differentiators. They might also give me periodic square waves or a step as the input and ask for what the output looks like for these. At one of the big tech companies they did ask for time domain response at each node, and the interviewer tried "breaking" the op-amp with diodes in very unusual places; it was not a practical circuit, but they were checking for understanding. All the interviews I've been on using KCL and KVL was very well-received. Sometimes they will ask a question related to having the output voltage being bigger than the supplies (say for instance your maths tell you it's going to be 5V, but the op-amp has a 3V supply), and also strategies to resolve this problem. Usually "reducing the gain" or "increasing the supply" is an acceptable answer, but they might follow up with an additional approach to solving that problem.

They'll ask about S-parameters. I'll typically have to draw a 2-port system and describe what each S-parameter by drawing out the arrows and labeling. They might ask for a 3-port system. I might be asked to draw any S-parameter plots for a broad or narrow band system. Sometimes they will ask me to cascade S-parameters. I think they run into a lot of people who thinking multiplying is okay (it's not). This might lead to talking about Y and Z-parameters, and ABCD matrix, but that doesn't happen always.

At the very least I am almost always asked about noise figure and linearity, and sometimes what it looks like on instruments such as a spectrum analyzer (or how to measure it). This is a good spot to trick candidates into asking about measuring the third order intercept; also to compare third order intercept to P1dB. Big tech companies will usually ask about units of noise and how noise is measured for a PSD. They might ask where in the chain would you prefer the best or worst noise figure and linearity in a chain; this may or may not lead into architecture questions. If it does, then you might have design a transciever on the fly and perform a link-budget. They usually do not provide the values I have to make it up roughly from the systems I've seen. This part of the interview is tricky because you might be "right", but for the "wrong" field (aerospace/defense versus consumer electronics). They might also ask which device in the chain is usually the least linear; what each filter does and how to roughly define its bandwidth. Only one place has asked a lot of questions about modulation schemes.

I'm always asked about layout and its flow. Particularly the cross-section of microstrip, stripline, and sometimes (grounded) CPW. They'll usually ask something like "If the characteristic impedance is too low we'll say $30 \Omega$ then how to correct it. You can do anything." Then you'll respond by how you can change the geometry of those transmission lines ie. if the impedance is too low you correct it by thinning the lines or thickening the dielectric, or (for CPW) widening the slot; you can choose a material with a lower dielectric constant. Sometimes they'll ask for "typical" dielectric constants and loss tangents. I'll also be asked how to choose which transmission line I'll use in a design (what are the advantages and disadvantages of each one). I've been asked once to draw the fields. I've also been asked to show what a stack-up looks like usually a 4-6 layer one and how to choose that as well, which layers will be dedicated to signal, power, and ground. A few places have asked about the process of making that stack-up and DFM questions.

I'll be asked about which tools I use. Any layout or simulation tools. This part usually also gets scrutiny even though you've disclosed which tools you use on your resume. Say for instance if you do layout usually with "layout tool 1" and you're interviewing for a position that uses "layout tool 2", then even though one person on the team thought the layout concepts were good enough there are still always people who do not care; it'll be difficult to convince them that you can learn and translate your knowledge between tools. I recommend if you are interested in working for a company find out which tools they use and try to get your hands on it; at the very least the (legal) free versions say for instance if they find Altium desirable then the free counterpart is CircuitMaker. I don't see this problem when talking about simulations, but I'm considered very proficient with many of them including the ones I've heard others call "the gold standard." For both layout and simulations you might be able to find workshops on the company's website.

Modern RF engineers still use Smith charts. I've never had an RF interview that does not use a Smith chart. This is usually a brief 5-10 minutes of the interview. I have no idea why many of my older coworkers will try dazzling me with it as if it were some mysterious object they got from an archaeology dig site in a seventh world country. The most typical questions are asking to create a matching network given a load; I also be asked questions about short and open stubs and compare them for when they are less than, equal to, and greater than $\lambda/4$. I'm rarely asked about Q factor and resonance although I've been asked; I've also been asked what the typical impedance (orders of magnitude) at different terminals of transistor looks like.

I have layout experience and so they'll continue with layout asking about a few approaches, component placement, and they might draw out a few areas of a trace or plane and ask you a few questions about it ie. they'll draw a trace going over a gap. I've had components placed for differential pairs. Roughly where I'll want to put "noisy" parts, and components such as LDOs or PAs known to get hot.

When LDOs get brought up sometimes we steer into switched DC-DC converters. I've had derive a buck, boost, and buck-boost during the interview. One of the big tech companies also asked me to show switch implementation (instead of using an ideal switch in drawing to use diodes and transistors). When the transistors get brought up here they might ask for the drawing of the cross-section of a MOSFET; they'll also ask about parasitics and how it affects the converter, and whether I would choose a pmos or nmos in certain areas and why. Because we're talking about converters we might talk more about PI and how to choose passives such as bypass capacitors.

For these rest I've probably been asked once or twice... do bode plots and Nyquist contours. Also using data converters I might even be asked to draw something conceptual or a block diagram of something connected to a data converter. A bit on sampling theory and folding. Some problems on measuring very tiny resistors or components on a layout (what might be wrong if I'm measuring $500\Omega$ when I was expecting $50m\Omega$. I'll be asked about protocols like SPI or I2C. Someone had me use the propagation constant of a distributed elements to give them $C_{eff}$ and $L_{eff}$. I've been asked about NEXT and FEXT also how to minimize or eliminate that. I've been asked how to convert differential into single ended. I've been asked coding questions; usually C or python is good enough. I've noticed that a common programming question will be play with the ++ or -- in front of the variable inside of a loop to see how the answer changes (if at all), and also logical operators including bit-wise ones. One interview asked me to prepare a presentation on a past project and I had to present it. Another interview (it was for an application engineer role) asked me to teach the interviewer something I was very comfortable with, which was surprising, but fun :). I think these last two I would prepare something even if you don't bring the powerpoint for the past project they might ask about it and it's great to refresh on what the project was, what challenges there were, and how you overcame it or why you couldn't. Trying to come up with something to teach during the interview can be scary so I would have a go to topic.

I had a bad gpa. I am always asked about my gpa. Big tech companies usually ask for you transcript; if not during the interview, then prior to getting an offer letter or at the very least when you are onboarding (if you are).

Salary expectations are almost always asked. I've seen general advice online is usually to try and dodge that question. I've never been successful in dodging it. Definitely come in with a number in mind and if you want to try dodging it then go for it, but if you can't then at least you came prepared.