Analog electronics

The goal of this course is to create a deep understanding of analog CMOS building blocks, ranging from elementary one-transistor circuits to circuits with a complexity level of operational amplifiers. Rather than focusing on calculations with network analysis techniques to derive circuit properties like gain, input or output impedance, the goal is to make interpretations, e.g. by means of feedback theory, that are the seeds to build intuitive insight in analog circuits. Having such insights enables to become creative at the circuit level and opens the door to a correct understanding of any other analog circuit. The students will be learned to design in a structured manner. The use of Matlab, in the lab sessions, will be helpful here. The lab sessions comprise the design of a CMOS circuit of the complexity of an operational amplifier. The emphasis is on structured design that should lead to a solid design plan, that will be coded in Matlab. Calculations of circuit properties using Matlab will be compared to simulation results of the circuit.  

The different parts of the course are:

1. Operation of downscaled MOS transistors

Interpretation and modelling of weak, moderate and strong inversion, second-order effects due to downscaling of transistors (e.g. velocity saturation, short-channel effects). Hence, we go much further than the elementary
quadratic model of a MOS transistor. Further, all elements of the small-signal equivalent circuit are considered.

2. Small-signal analysis of linear and weakly nonlinear circuits
   Calculation of transfer functions, interpretation of their poles and zeros
   Nonlinear distortion: harmonic and intermodulation distortion, intercept and compression points, distortion in a cascade of nonlinear circuits
3. Noise behavior of analog circuits
   Thermal noise, shot noise and 1/f noise, calculations of noise in circuits
4. Feedback in analog circuits
   Impact of feedback on gain, distortion, sensitivity to variations.
   Different feedback configurations
   Calculation of the loop gain including the effect of loading

Stability of feedback circuits

5. Elementary circuits
   Analysis of elementary circuits (common source, common drain, common gate, source degeneration) in terms of feedback, interpretation of their operation, noise and frequency behavior.
   Diode-connected transistor, current mirrors, CMOS inverter, cascode stage
6. Differential circuits
   Differential and common-mode gain, impact of mismatches, extension to mixer, comparator, frequency multiplier, oscillator with cross-coupled pair.
7. Operational amplifiers and operational transconductance amplifiers
   Design of the signal path and the biasing circuitry for several widely used topologies, such as the Miller-compensated one and a folded cascode one. Gain, frequency response, stability, common-mode gain, noise analysis will be considered.

After this course, students should be able to effectively design such circuits with properly sized transistors and well-chosen bias levels, taking into account realistic (= industrially relevant) specifications. This course enables students to become creative at the circuit level and opens the door to a correct understanding of any other analog circuit. In the lab sessions, leading to the sizing of a circuit such as an operational amplifier, students will learn to think about the sizing and bias level of each transistor. Going through such process in a structured way is helped here by coding the design reasonings and trade-offs in a Matlab script.

Required and Corequired knowledge and skills

Students need to have
- basic understanding of solid-state physics including an understanding of the basic operation of a MOS transistors and p-n junctions.
- network analysis: ability to set up network equations in the frequency domain for linear(ized) circuits
- transfer functions, Bode diagrams, Laplace and Fourier transforms
- elementary control theory: stability of linear feedback systems, phase margin 
- understanding of impedances, Norton and Thevenin representation
These items are usually taught in courses on Electromagnetics, Physics, Quantum physics of electronics, introductory control theory, network analysis, introduction to Electronics

Courses requiring this course

The course is common to the first Master year of Electrical Engineering of VUB and ULB. There is a syllabus in the form of a fluent text. It is made available to the students via the Canvas platform of VUB. There are 42 hours of regular courses, including an introduction to the practical sessions. The latter ones comprise 20 hours, during which an operational amplifier is designed. These practical sessions make use of Matlab and LT Spice. Teaching assistants are guiding these sessions.

References, bibliography, and recommended reading

The course material is self contained: no extra external sources need to be consulted. However, the field of analog circuits is very broad. Below you can find some sources of complementary study material if you want to deepen your knowledge beyond the course material.

• A. Sedra, K. Smith, T. C. Carusone and V. Maudet, "Microelectronic Circuits", Oxford Press 2015.
• B. Razavi, "Design of CMOS analog integrated circuits", Irwine Electronics and Computer Engineering, 2016.
• Paul Gray et al., "Analysis and design of analog integrated circuits," 5th edition. New York: John Wiley, 2010.

(very well readable introductory work to the design of analog integrated circuits. Emphasis is mainly on circuits with bipolar transistors, but in the last version the amount of CMOS circuits has increased.)

• Kenneth Laker and Willy Sansen, "Design of analog integrated circuits and systems", Mc Graw Hill, 1994.

(this book presents an in-depth analysis of elementary transistor circuits (both in MOS and in bipolar);

opamps are treated in more detail than in the book of Gray & Meyer. Also, the design of active filters (both continuous time and switched capacitors) is discussed.)

• Yannis P. Tsividis, "Operation and Modeling of the MOS Transistor," Mc Graw-Hill International Editions, 1988.

(excellent up-to-date book on the operation of MOS transistors, useful both for designers as for device specialists)

• Behzad Razavi, "RF microelectronics", Prentice Hall Communications Engineering, 2011.

(very well readable and structured book on high-frequency (RF) integrated circuits. The book covers both architectures of transmitters and receivers and the subblocks of the architectures (low-noise amplifiers, oscillators, mixers, power amps, ...))

• Thomas Lee, "The design of CMOS radio-frequency integrated circuits," Cambridge University Press, 2004.

(very well readable work about high-frequency (RF) integrated circuits. Covers a broader range than Razavi, but little computations)

• Piet Wambacq en Willy Sansen, "Distortion analysis of analog integrated circuits," Kluwer Academic Publishers, 1998.

(introduction to the nonlinear behavior of analog ICs)

• Design of Analog Filters, Passive, Active RC and Switched Capacitor, Rolf Schaumann, Mohammed S. Ghausi, Kenneth R. Laker, Prentice Hall, 1990

(reference work for the design of active and passive filters)

Course notes

• Syllabus

Contacts

Please contact prof. Piet Wambacq for more information via Piet.Wambacq@vub.be

Campus

Other campus

Method(s) of evaluation

• Oral examination
• Other

Oral examination

• Open book examination

• Open question with short answer

Other

There is an oral examination that takes one hour: you get one question, typically a circuit that you need to understand and give a simplified expression of a property like gain, input or output impedance, dominant pole. Network analysis is not needed or reduced to a strict minimum. Instead, insight in the circuit together with approximate formulas of small circuits that have been treated in the course should enable you to solve this question properly. For this question, you can consult the course notes. To prepare your answer to this question, you get 30 minutes. After these 30 minutes, the oral part begins. In that part you explain your answer and you will be interviewed on the CMOS circuit that has been designed in the lab sessions.

Mark calculation method (including weighting of intermediary marks)

The main criterion whether or not a student passes the course is that the student has to show at the exam the ability to build up reasonings about analog circuits of the complexity of operational amplifiers. Both the single question with the unknown circuit and the interview on the opamp design are the means that prof. Piet Wambacq uses to evaluate this ability. 

Language(s) of evaluation

• english