ANALOG ELECTRONICS

The objective of this course is the analysis, the simulation, and the design of feedback circuits with particular emphasis on single and multi-stage amplifiers.

Knowledge and understanding

The course will focus on the design of circuits in CMOS technology and will guide the student in understanding the main configurations of single-transistor circuits (common source, common drain and common gate) and those with multiple transistors (current mirrors, cascode amplifiers and differential amplifiers). The student will also know the static and dynamic properties of feedback circuits, as well as the techniques of circuit analysis and design. The course will be completed by some topologies of current/voltage references and by structures of feedback amplifiers commonly used in integrated technology.

Applying knowledge and understanding

At the end of the course the student will be able to analyze the behavior of a feedback circuit using a “pencil-and-paper” analysis and to simulate its main characteristics. The student, with the help of the computer, will also be able to design the compensation network of a feedback circuit with one or two gain stages and to design the most common topologies of integrated amplifiers. The student will also be trained in the use of the Cadence design environment.

Making judgements

Starting from the technical specifications, the student will be able to design common topologies of integrated amplifiers by autonomously making the appropriate design choices. Numerical exercises, computer simulations and the development of a design project will sharpen the making judgment skill.

Communication skills

The student will improve the technical language of analog electronics and will be able to interact with colleagues in a team to discuss appropriate solutions to a specific design problem. For this purpose, during the laboratory lessons, students will be grouped into small teams. The final report and oral exam will also help to refine the technical language and communication skills.

Learning skills

Students can broaden their knowledge of analog electronics by studying recommended textbooks or reading scientific articles published in specialized journals and through the insights offered by seminars organized within the course.

The course includes 87 hours of lectures (42 hours of theory, 30 hours of numerical exercises and 15 hours of laboratory lessons) accompanied by 30 hours of tutoring activities. The practical activities focus on the use of the Cadence design environment and on the development of a design exercise that will be described in a project report. The laboratory experience will be aimed at putting into practice, developing and consolidating the theoretical contents and design techniques learned. Finally, seminars held by researchers and designers from industries operating in the microelectronics sector will be organized.

Should teaching be carried out in mixed mode or remotely, it may be necessary to introduce changes with respect to previous statements, in line with the programme planned and outlined in the syllabus.

Attendance is not mandatory but strongly recommended. Students who have not attended laboratory lessons for at least 70% of the scheduled hours will not be able to complete the project report and will have to take a written exam.

Bipolar transistor models

The pn junction. BJT forward active region. Large-signal dc models. Operating modes. Small-signal models. Parasitic elements.

MOS transtor models

MOS structure and operating regions. MOSFET operating regions. MOSFET I-V characteristic. Large-signal dc models. Small-signal models.

Basic MOSFET circuits

MOSFETs’ external resistances. Single-transistor circuits(CS, CD and CG). Current mirrors. Differential amplifiers. High-gain stages. BiCMOS stages.

Frequency response

General amplifiers' structure. Seeking poles and zeros. Single transistor stages: CS, CD and CG. Current mirrors. Differential pair. High-gain stages. 

Amplifiers dc analysis

General amplifiers' structure. Feedback. Two-port theory. Return ratio. Rosenstark method. Blackman method

Amplifiers ac analysis 

Feedback amplifiers' general characteristics. Stability analysis. Stability criteria. Compensation techniques.

Voltage and current reference circuits 

Voltage/Current reference parameters. Current reference circuits. VBE vs T modeling. Bandgap voltage reference circuits: Widlar, Brokaw, Kuijk and Banba.

Operational Transconductance Amplifiers (OTAs) 

Two-stage class-A OTA. Stacked mirrors OTA. Folded cascode OTA

The Cadence Design Environment

Design of electronic circuits by means of Cadence

1. Gray, Hurst, Lewis, Meyer, Analysis and design of Analog Integrated Circuits, 5th Ed., John Wiley & Sons, Inc.
2. J. Millman & A. Grabel, Microelectronics, McGraw-Hill.
   
3. Alan B. Grebene, Bipolar and MOS Analog Integrated Circuit Design, John Wiley & Sons, Inc.
4. P. R. Gray, R. G. Meyer, Circuiti Integrati Analogici, II Edizione, McGraw-Hill
5. A. Vladimirescu, Guida a SPICE, McGraw-Hill Libri Italia.
6. Cadence Online Manuals.

Learning assessment is verified through the final exam. 

Exclusively for the first session of exams (winter session), the final exam consists of an oral exam preceded by the evaluation of a project report.

For all the other sessions, the final exam consists of an oral exam preceded by a written test lasting 2 hours. Regardless of the session, this procedure will also apply to students who have not attended laboratory lessons for at least 70% of the scheduled hours and to students who have obtained a negative evaluation in the project report or have not delivered it within the deadline.

The project report is a brief description of the analysis and design of a feedback circuit that students, in groups of two, will discuss during laboratory hours. The document must include:

1. Sizing of circuit components to achieve a specific bias point (“pencil and paper” evaluation of the bias point an comparison with simulation);
2. Evaluation of the loop-gain transfer function and design of the compensation network (“pencil and paper” evaluation, simulation with initial design values and subsequent fine tuning via simulator);
   
3. Evaluation of the asymptotic gain and input (or output) resistance using the Rosenstark and Blackman methods (“pencil and paper” evaluation and comparison with simulation results);
   
4. Simulation of the DC input-output transcharacteristic and evaluation of the signal swing;
   
5. Simulation of the closed-loop bandwidth of the circuit;
   
6. Simulation of the step response and evaluation of the settling time;
   
7. Simulation of the large-signal step response and evaluation of the slew-rate;
   
8. Simulation of the time response to a sinusoidal signal and evaluation of the total harmonic distortion.
   

The teacher will interact with the different groups during the laboratory lessons. Students, in turn, can interact with the teacher, keeping in mind that they are taking a part of the final exam. At the end of the course, the groups can interact only once with the teacher to verify the correctness of what they are doing (note that in this period the student is taking his/her own exam, therefore he/she cannot be admitted to the office hours for clarifications on doubts or questions). 

The report must be delivered in pdf format to the teacher's email address at least one week before the first exam of the winter session. The report will be evaluated as PASS/FAIL. In the case of negative evaluation, the student must take the written test to be admitted to the oral exam. The list of students admitted to the oral exam will be published on the Studium platform (http://studium.unict.it) or on the Teams channel of the course, in time to take the oral exam.

The written test lasts 2 hours and is preparatory to the oral exam. It is mandatory for all exams that take place outside the winter session. It is also mandatory for students who have not attended laboratory lessons for at least 70% of the scheduled hours and for students who have obtained a negative evaluation in the project report or have not delivered it within the deadline.

The written test consists of the analysis of a feedback circuit and the design of its compensation network. Typical requirements are: 

1. Evaluation of the bias point;
   
2. Evaluation of the loop-gain transfer function and design of the compensation network;
   
3. Evaluation of a closed-loop parameter (e.g., asymptotic gain, equivalent resistance at a node).
4. Evaluation of the input and/or output signal swing.

The written test must demonstrate the student's ability to correctly analyze a feedback circuit. Specifically, the evaluation will take into account the ability to correctly identify and analyze the elementary circuits studied in class, the ability to identify and design the appropriate compensation network and the ability to correctly apply the analysis techniques for feedback circuits. For each point, the evaluation of the test will also take into account the correctness and coherence of the procedure, the clarity of the presentation, the correctness of the numerical calculations (where required) and how much the student was able to complete. The result of the written test, published on the Studium platform (http://studium.unict.it) or on the course Teams channel, is expressed through a rating scale (FAIL, POOR, PASS, FAIR, GOOD). Students admitted with POOR will have a limitation on the final mark (max 25/30).

The oral exam is the last part of the exam and consists of two questions on two topics of the course. In the answers, the student must demonstrate adequate understanding, mastery of the topics discussed and clarity of exposition. Students who have completed the project report, may be asked an additional question on the project itself. The average duration of the oral exam is 40 minutes. The final mark will take into account the work done in the laboratory lessons, the quality of the design report (or the outcome of the written test) and, most of all, the result of the oral exam.

Learning assessment may also be carried out on-line, should the conditions require it.

To ensure equal opportunities and in compliance with current laws, interested students may request a personal interview in order to plan any compensatory and/or dispensatory measures based on educational objectives and specific needs. Students can also contact the CInAP (Centro per l’integrazione Attiva e Partecipata - Servizi per le Disabilità e/o i DSA) referring teacher within their department.

Examples of questions for the oral exam

• Small-signal model of the bipolar transistor
• CMOS current mirrors
• Frequency response of the differential pair
  
• Blackman method
• Stability criteria of feedback circuits
• Selfbiased current mirrors
• Stacked mirror operational amplifier

As far as the written test is concerned, Studium platform (http://studium.unict.it) contains several test examples assigned in the past academic years.