ANALOG CIRCUIT DESIGN
For an ECE undergraduate there are a gazillion options after college, but people who aim at acquiring a core job, the job categories mainly narrows down to 3 prominent fields of core ECE jobs:
1. Digital design (ASIC, FPGA, Embedded Firmware etc)
2. Analog Design (Analog circuit design, Vaidation etc)
3. Communication (Wireless 4G, 5G, GSM etc)
I will be discussing here today the roadmap and resources to be followed to get the hang and mastery of subject which has been given many names by generations of students, some call it “a work of mystic arts”, for some it is a “Nightmare” while others say it’s “As easy as a pie”! i.e ‘Analog Electronics’, and some bare-minimum skills that you require to ace an Analog profile based interview.
Let me begin with stating -“Analog VLSI” is a misnomer. Because the term “Very Large Scale Integration (VLSI)” is applicable only to digital circuits where the transistor / gate count is in millions. So, Analog VLSI is Analog Design predominantly it is based on a Complimentary Metal Oxide Semiconductor ( CMOS ) platform and hence most often than not it is CMOS Analog Design.
The primary difference between Analog and Digital circuits is that the former deals with Analog Signals ( continuous in time and continuous in amplitude / space ) while the latter deals with Digital Signal ( discrete in time discrete in amplitude / space ). In order to work with analog signals the analog circuits needs to be biased in their linear operating region, while the digital circuits need no biasing and they can operate in non-linear / switching mode.
The world may seem like it has been shifted to digitized circuits yet the heart of most circuits has some intuitive Analog circuit design engineers who, along with their mystic tools, acquired through persistent practise and sheer resilience are designing ADC’s(Analog to Digital convertors), Sensors, Filters etc. so that the circuit is capable of interacting with the real world and is able to acquire information form it.
Getting straight to the point, some continual and serious practise sessions are required to get the feel of this subject because everything that you will learn here, is connected to what you will learn in future, that means, you cannot learn this subject overnight, the knowledge acquired is layered. The layer by layer knowledge will pave your way to some amazing opportunities in the semiconductor industry!
Although the pointers are generalized with both job point of view as well as future research, yet the pointers that I will mention here are mostly related to cracking the interviews for internships and jobs for some leading semiconductor companies. (For eg. Texas Instruments, Qualcomm, STMicrocelectronics, ARM, Intel etc)
This is going to be the most detailed roadmap that you will find anywhere over the internet for an ECE fresher, because I will tell you everything that I know, The info given here is verified by industry experts and is a generalization of the trend of interviews being conducted by semiconductor companies in India.
• NETWORK ANALYSIS AND SYNTHESIS: (Takes about 2 months for thorough practise)
To begin with, the subject which requires the most detailed understanding as a pre-requisite for Analog circuit design is ‘Network Analysis and Synthesis’. The circuits, even the most complex ones would become a piece of cake for you if you understand and practise lots and lots of questions from Network Analysis.
Important topics that will surely come handy:
1. A solid understanding of voltage, current, resistors, capacitors, inductors etc.
2. KVL, KCL, nodal, mesh etc.
3. All the theorems Thevenin, Norton, Max. Power transfer etc.
4. Sinusoidal Steady state analysis of RLC circuits.
5. Resonance in RLC circuits
6. Transient response.
7. Laplace in RLC circuits
8. Two-port network analysis
9. Graph theory
10. Passive filter/analysis using R, L and C.
I would like to emphasize on the fact that, while all topics in the book - Circuit theory by A. Chakrabarti are prescribed to be covered in one semester(3rd usually) by you (doesn’t matter what the curriculum your college is) still the topics/chapters that I mentioned above are serious things that you won’t be able to survive without in the Analog field.
Note: Following A chakrabarti is enough for practise but if you wish to dig deep you may purchase ‘Network Analysis by M.E Van Valkenburg’, it has less practise problems, but is a good read if you have enough time.
The theory and lectures are available on Youtube.
NPTEL Lectures on Circuit theory
>>Softwares for Simulation
1. Tina T.I
• CONTROL SYSTEMS: (Will be covered in college curriculum)
This is yet another crucial building block that an aspiring Analog engineer must possess in his tool-kit. The approach for tackling this subject is pretty much straightforward, the main topics that need to be done with very good understanding are:
1. Laplace and Transfer function
2. Time domain analysis of Control systems
4. Frequency domain Analysis of Control systems
5. BODE Plot(Most important)
This is important as this subject gives an introduction to feedback and frequency domain analysis, after getting the hang of it, the student understands the reasoning beyond this and the meaning on why are doing this.
The only Book to be followed: Control systems by Samarjit Ghosh
Lectures and Online help:
1. NPTEL lectures on Control systems
2. UDEMY - Control Systems: From Mathematical Modelling to PID Control (If after completion of your syllabus you find yourself interested in learning how to control machines accurately and effectively, this certified course can be done which also gives you a hold on ‘PID’).
• TRANSISTORS (Will require at-most 2 semesters with continual practise)
This is your starting point in the world of Analog electronics, and has to be taken most care of.
We will be following a fool-proof method to get the most out of the resource that I will be mentioning here as well as the practise that you will be doing alongside following the resources. The section of transistors consists broadly of 3 parts
1. Semiconductor Physics
There are newer technologies available in market these days, like FinFETs but they are not in your syllabus as of now and if they’ll be included in your curriculum, I will update it at some point later in time.
Moreover, this blog post is created for students aspiring to get jobs and internships in the field of Analog Electronics so the main focus of yours shall be on Transistors, They are the heart and soul of the semiconductor industry, whatever you learnt until now, Networks, Control etc, were just tools that will greatly enhance your understanding while tackling this subject!
I have to repeat this time and again, There is no short-cut to success, especially in Analog, you can’t remember all these information overnight.
This is a dedicated process and requires intuitive thinking. Once you have done enough practise all the concepts given in this blog post(by enough I mean more than 5000 questions), you will notice your brain’s superiority over others.
The circuit, whatever it shall be, will begin to solve itself, This intuition is required in this field and trust me, no one is born with this type of intellect, this is sheer practise, and people aspiring core companies have to stand out from the crowd!
I guess that’s enough motivation for beginning with the most crucial part of you journey TRANSISTORS!
1. Starting with Semiconductor physics:
Get the best at it, derive as much equations as you can and most importantly know the physics behind whatever is happening. The maths alone never helps, you need to find a way to visualise the equations until they make sense to you else the technique fails.
(Note – This is in itself a domain with good research scope)
The resources that I provide here will be invaluable to your preparation:
• Start with lectures by Dr. Behzad Razavi(Lecture 1 to Lecture 12).
PN junction and diode modelling lectures by Dr. Razavi
• Then read the corresponding theory and practise corresponding problem sets from his book
Microelectronics by Dr. Razavi
• Read and practise further from Microelectronics by Sedra/Smith
• Courses for Online certifications : Semiconductor Specialization
2. Starting with Bipolar junction Transistors:
Some important concepts that must be understood by heart
1. Small and large signal modelling
2. Early Effect
3. Bipolar amplifiers
4. Common emitter with degeneration etc.
5. Common Base/Collector
6. Biasing techniques(Most important)
Get the hold of all the theory from Dr. Razavi’s lectures(Lecture 12- Lecture 28).Trust me, the understanding and the depth provided in these lectures are invaluable.
Continue doing a rigorous practise of the above learned concepts from his book Microelectronics by Dr. Razavi
If you have enrolled yourself in this course Semiconductor Specialization while studying semiconductor physics you’d know that this covers BJT too. Also I’d like to mention this is an invaluable specialization and will come very handy during interviews.
Lastly, I’d say practise practise practise! There’s is no substitute to it. The course contents and topics that are covered in BJT may seem overwhelming at first, but once you understand the bigger picture, you’ll actually love every circuit that is given to you to solve and will soon be able to design your own amplifier and various other circuits! Voila! Your first step towards a career in Circuit design.
Some of the concepts like h-parameters re-model, that are not explained by Dr. Razavi in his lectures and book, can be done from here: NESO ACADEMY- Analog
>>Softwares for simulation
1. LTSpice (Free)
2. Multisim (Free for trial period)
Once you have simulated enough circuits go to the lab, grab a multimeter and measure and verify your results, measure the voltages across emitter/collector, measure the terminal currents, make note on how the small signal model although looks complex but is the most powerful tool while solving transistor based circuits!
3. Metal Oxide Semiconductor Field Effect Transistors
The reason I mentioned the full name for MOSFETs is that, the name, in itself defines the structure and making of these seemingly strange yet magical devices!
The MOSFET is a relatively new device as compared to BJT, and is considered faster, cheaper and more efficient with minimal static power dissipation(CMOS) (Which you’ll learn about later in the course, don’t be alarmed) . MOSFET is one of the favourite topic of interviewers in the semiconductor companies, you have to learn everything you can about them and beyond that too!
To begin with, Start from Lecture 29 (Intro to MOSFETS) of Dr. Behzad Razavi’s lectures and then read about it from his textbook. After completing you may proceed with the following lectures while following the same pattern as followed above for BJT.
Some of the Important concepts that must not be omitted
1. Construction of both depletion/enhancement type MOSFET
2. Significance of Transconductance/Channel length modulation
3. Common emitter/source/drain and all these stages.
4. Biasing techniques
5. CMOS Inverter
6. CMOS digital gates designed
7. Static/dynamic power dissipation
8. CMOS Amplifiers
9. Cascode stages/current mirrors
The course for online certification remains the same as it is a specialization of Diodes, BJT and MOS: Semiconductor Specialization.
>>Softwares for Simulation
1. Cadence Virtuoso Analog design Suite. (Licensed)
Once you understand all the theory and have practised enough questions, you may get started with one or two projects from here: HACKSTER MOSFET projects
Projects are an essential part of the learning curve and it primarily gives you a reality check!, as everything that you have been learning and solving is utilised in real life too, nothing is boring in Electronics, as every concept can be covered while doing projects.
I would greatly emphasize on taking this online certification and understanding the underlying physics of MOS being taught in this course MOS Transistors, This certification will hold great value during interviews as it is considered a fairly advanced course, but then again, a little more information never hurt anyone!
You have successfully completed 60% of your preparation!
• OPERATIONAL AMPLIFIERS (In the semester following transistors, cover this)
Op-amp is a versatile device that is used to amplify DC as well as AC input signals and was originally designed to perform addition, subtraction, multiplication and integration.
This comes after BJT and MOS and is the most important topic if you are preparing for interviews in core companies based on semiconductors (For eg. Texas instruments, Qualcomm etc). Therefore a full-on mastery of this subject is quintessential!
Some important topics to be covered at all costs:
1. Frequency response of an Op-amp.
2. Active filters.
5. Phase locked Loop
6. Automatic Gain Control
7. Universal active/Switched capacitor filter.
The main focus for this subject should remain on covering nook and corner of this book
Linear Integrated Circuits by Ramakant A. Gayakwad
After its completion you can move on to more advanced texts:
1. Sergio Franco
2. Microelectronics by Dr. Razavi (Op-Amp chapter)
The online lectures available on op-amps are kind of vast, you may follow two routes here:
1. If you are preparing in a hurry and just need to understand the concept and then will read and solve questions on it by yourself, learn from here - Youtube – Op-Amp
2. If you have enough time you may start from these NPTEL Lectures - Analog Ics
(This is the advised source to learn because this is very popular topic with interviewres and you don’t want to leave any stones unturned while preparing Op-Amps!)
The online certified course for Op-amp is quite useful as the instructor presents the practical use of op-amp at each step of explanation.
Please cover all the projects given from Page 476 in Linear Integrated Circuits by Ramakant A. Gayakwad, They are very useful for your practical understanding.
We are Almost done with the extensive preparation now all that is left are the things, that are quite complex and require a very good understanding of all the subjects mentioned above, but being able to understand the following topics from the specific resources will be an invaluable addition to your toolkit!,
It will benefit you during interview because the interviewer will surely be impressed by the vast knowledge pool that you are, and the most important thing is never memorize any formulae without understanding its significance!
Addition to your toolkit:
1. Differential Amplifiers (Pg 399) Microelectronics by Dr. Razavi
2. Frequency Response (Pg 460) Microelectronics by Dr. Razavi
3. Feedback and current mirros/cascode stages (Pg 513) Microelectronics by Dr. Razavi
Please watch ELECTRONICS 2 By Dr. Behzad Razavi.
4. Noise (Pg 219) Analog CMOS IC design By Dr. Behzad Razavi
5. An intro to FinFETs and their principle of operation.
6. Read about Silicon Photonics.
7. Know how the technology node shifted from microns to 22nm and even upcoming 7nm.
8. Be master to variety simulation software as well as a good hardware designer of circuits.
9. Cover more and More Projects related to the field, deepens the understanding.
10. Please have a good understanding of the subject “Signals and System” too, although not quite necessary yet is good to know in depth about fourier, laplace and Z transforms and the reasons why they are performed as well as their physical significance.
Be consistent, each day matters, each day you should be learning something or solving something, the syllabus is very vast and may seem overwhelming at first but trust me once you get past BJT, everything else will make sense and will be a rewarding journey.
If you will truly follow the blog post, you will be having in-depth knowledge in Analog that is required and expected from an undergraduate fresher as well as you will have enough Online certifications to prove your credibility in addition with the projects that you will undertake.
A synopsis of resources that you will collect during this journey!
>>Online certification courses:
1. Control Systems: From Mathematical Modelling to PID Control
2. Semiconductor Specialization
3. MOS Transistors
>>Books to be followed:
1. Circuit theory by A. Chakrabarti
2. Network Analysis by M.E Van Valkenburg
3. Control systems by Samarjit Ghosh
4. Microelectronics by Dr. Razavi
5. Microelectronics by Sedra/Smith
6. Analog CMOS IC design By Dr. Behzad Razavi
7. Linear Integrated Circuits by Ramakant A. Gayakwad
8. Sergio Franco
Here is bonus point to enhance your practical knowledge.
Udemy has a ‘Crash Course’, That is being taught by Dr. Andre Lamothe who is a renowned Computer scientist, Electrical Engineer, Mathematician as well as a Game developer. This course is to be joined from the beginning of first semester itself. This is 95 hour long course and is the most extensive course in the history of online courses!
The guy explains stuff theoretically and literally takes you to his lab and performs practical on each and every topic that he explains. Pretty insightful and knowledgeable I’d say!
Moreover there is a section on PCB DESIGN using ‘Circuit Maker’, which is must have tool in every electronics engineer’s pocket. This is a very essential skill that can easily land you a job, and this is an Advanced course at a very cheap price. It covers everything from Analog to Digital electronics, trust me you won’t be disappointed!
Embedded Hardware/Firmware Engineer