Ing Ind - Inf (Mag.)(ord. 270) - MI (476) ELECTRONICS ENGINEERING - INGEGNERIA ELETTRONICA
095380 - MIXED-SIGNAL CIRCUIT DESIGN
This course covers circuit and system level design issues of both analog and mixed-signal integrated circuits (IC).
Focusing mainly on CMOS and Bipolar technologies, the key building blocks, such as differential amplifier, voltage and current references, comparators, and the most important issues for the design analog and mixed-signal ICs , such as noise, power and offset, will be discussed in depth. Some topologies of DAC and ADC that are representative of an entire family of converters will be then discussed: current steering DACs, are studied an example of Nyquist rate converters, pipeline ADC, are an example of low-rate high-accuracy converters, delta-sigma DAC, are an example of oversampled systems.
The main goal, more important than the mere knowledge of a number of circuit topologies, is to encourage the typical intuitive attitude required in the IC design (and in many areas of engineering) i.e. to focus the main design issues and constrains, to individuate the trade-offs and, finally, to provide the optimum solution. This process must always precede the mathematical modeling of the circuit.
Each part of the program is discussed in “lesson” classes, more focused on the theoretical aspects, while “exercise” classes will provide some examples, often taken from the past written test.
This course presumes a solid understanding of the basics of analog circuits.
Risultati di apprendimento attesi
Being the classes intended as the final course on analog and mixed-signal IC design, the most important learning outcome upon passing the exam is not the knowledge of a list of circuits topologies but:
Knowledge and Understanding (Dublin descriptor 1)
To understand what are the trade-offs in the analog and mixed signal design
To critically discuss what are the possible solutions for the specific problem discussed.
The student should be able to understand that it does not exist an optimum solution for all the problems but the best circuit to adopt depends on the specifications (for instance gain, or linearity, or noise) and constrains (voltage supply, power, silicon area).
To be able to critically read the technical literature (journal paper and, of course, books), which is clearly a necessary skill for a designer given the huge amount of technical literature today available. To this purposes an example of design will be discussed with the help of a literature paper.
Applying knowledge and understanding (Dublin descriptor 2)
Select from the body of knowledge the useful skills to solve a given design problem.
Analysis both at system level and at transistor level of mixed signal circuits
Capability to design all the critical building blocks of a mixed signal circuit, given the specifications and the design constrains.
Critically analyze other proposed solutions.
Bipolar junction transistors (BJT)
Fundamentals of BJT physics and integrated BJT technologies, main difference with respect to CMOS.
Basic BJT stages. Bipolar OPAMPs.
Modern Bipolar technologies.
Components matching and offset
Deviation from the nominal value, and relative matching of integrated components.
Main sources of mismatch in CMOS and Bipolar technologies.
Matching in a differential stage.
Impact on speed and power dissipation.
Impact on DAC INL and DNL, example of design of a current-steering DAC.
Noise sources in CMOS and Bipolar.
Equivalent input noise generators.
Input noise for basic stages, and opamp.
Noise-power trade off.
Impact on design of sampled system and ADC.
CMOS and BiCMOS stages
A short review of the basics: Input stage. Level shift. Slew rate. Frequency compensation. CMRR and its link with offset. PSRR.
Fully differential stages. Common mode feedback network.
Output power stages, distortion.
Feedback and distortion.
Bipolar output stages. CMOS output stages.
Voltage and current references.
Voltage and current references derived by Vbe and Vt.
Bandgap reference: theory and circuits.
CMOS and BiCMOS comparators. Basic structure.
Nyquist rate current steering DAC: INL and DNL. Thermometric vs. binary architecture.
Delta Sigma DAC
High resolution ADC: Comparison between pipeline, SAR and Delta sigma.
Advanced techniques and figure-of-merit.
There are no official prerequisites for this course.
A standard background in analog electronic is however assumed. In particular:
The main characteristics of CMOS technology and the working principle of CMOS: static characteristic, transconductance, frequency response.
The basics of feedback circuits operations (virtual ground, loop gain).
The fundamental transistors stages configurations (common source, source follower, cascode, differential pair)
Basic circuits adopting an ideal Op-Amp (inverting and non-inverting stage, integrator).
The topics discussed in Analog Circuits Design (5247) and Electronic Systems (88724) cover all the prerequisites
Modalità di valutazione
The course ends with a 2-hours written exam consisting in the analysis of a circuit, in term of its main performance, followed by a mandatory oral (viva) test. The circuits in the written test are always the building blocks discussed in the first part of the course, typically amplifying stages. Examples of past written test will be discussed and solved during the exercise classes.
The written test will be followed, for students that passed the written test, by a mandatory oral (viva) test, consisting in a discussion about all the topics discussed in the classes.
The description of each type of assessment is as follows:
Written test: Two hours. Evaluation of the main performance of a given circuits, usually an amplifying stag. Typical questions deal with: gain, noise, offset, slew rate and bandwidth). (Dublin descriptor 1 and 2). A final question is added to stimulate the open discussion about different circuits' solutions (Dublin descriptor 1,2) during the following oral test.
Oral (viva) test: Usually 20-30 minutes. Theoretical and practical questions, focused on design choices, picked from all the topics in the program discussed during classes (Dublin descriptor 1 and 2).
The final grade is given to the student after the oral (viva) test.
The date of the written test is published on-line on the POLIMI webpage. The oral (viva) test will be held usually within 1-2 days after the written test, once the teacher will have evaluated the written tests and informed the students.
Any student can withdraw at any time during both the written and oral test and may also decide to repeat the entire exam if he/she wants to improve its mark. It is not allowed to repeat only one part of the exam (that is either only the written test or only the oral test).
P. Gray, P. Hurst, S. Lewis, R. Meyer, Analysis and design of analog integrated circuits, Editore: Wiley an& sons, Anno edizione: 2009 Note:
The book contains much more material that the one covered by the course, however it is the classical book and the reference for analog designer, and it will be useful for everyone the will work in this field.
Franco Maloberti, Data converter, Editore: Springer
Tipo Forma Didattica
Ore di attività svolte in aula
Ore di studio autonome
Laboratorio Di Progetto
Informazioni in lingua inglese a supporto dell'internazionalizzazione
Insegnamento erogato in lingua
Disponibilità di libri di testo/bibliografia in lingua inglese
Possibilità di sostenere l'esame in lingua inglese
Disponibilità di supporto didattico in lingua inglese