# APPLIED ELECTRONICS

- Scheda dell'insegnamento
- Obiettivi formativi
- Prerequisiti
- Contenuti
- Metodi didattici
- Verifica dell'apprendimento
- Testi
- Altre informazioni

The goal of the course is to provide the students with concepts and methods both to understand the behaviour of complex electronic circuits and to design an electronic circuit on the basis of specific requirements. Such a course could be of interest for students that intend to work in the field of experimental particle physics, of applied physics (such as medical and environmental physics) and all the physics fields in which analog and digital electronics are involved (optics, instrumental astrophysics, space physics).

To reach the course goal, the theoretical description of components and circuits is verified with simulation tools comparing the results with the acquisition of data in the laboratory with “real” components.

At the end of the course, students will be able to:

- describe the different components of analog and digital electronics, using both simple and more complex models, and their use in complex circuits

- explain critically the “real” behaviour of components and circuits (for instance, considering the temperature variation)

- describe the different components of a circuit, identifying the role of each element and the way they are connected together, making assumptions on the performance of the circuit before its assembly

- design the readout chain of a detector, defining each element and its role and simulating its performance.

To better understand the topics treated in the course and perform the practical activities, it is advisable that students possess bases of programming and maths, as acquired during the bachelor course.

INTRODUCTION TO SIGNAL PROCESSING

- Signal formation and conversion: definition of the involved parameters and of the common features of detectors

- A complicated example: the Time Projection Chamber, to understand the meaning of speed, signal to noise ratio, pileup and the elements of a readout chain

- Review of basic concepts: components (resistors, capacitors and inductors), the Ohm and Kirchoff laws, voltage and current generators, the voltage divider, Thevenin’s theorem

FROM TIME DOMAIN TO FREQUENCY DOMAIN

- Ideal vs real systems: how to define the response function of a system

- Time domain analysis: the computation of the response function of a linear system with time invariant concentrated constants, using the convolution integral

- From time to frequency domain: definition of the Laplace Transform; examples of the transform of standard functions

- Network theory in the frequency domain: definition of current and voltage generators and of the components in the frequency domain to obtain the generalized Ohm equation

- Network theory applied to standard circuits to understand the transitory behaviour: RC, RL and RLC circuits with a step, a sinusoidal and a pulse input

- The transfer function to describe the behaviour of a circuit given the input signal: zeros and poles of the transfer function, generalized synusoids, Bode diagrams

DIODES

- Review of the physics of pn junctions

- IV curve for different types of diodes

- Applications: half wave and full wave rectifying circuits, signal rectifiers, clamping

- Diode features: the diffusion junction diode and the Schottky diode; the importance of the reverse recovery time

TRANSISTORS

- Review of the basics: the physics of the npn (pnp) junction and the 4 working rules of transistors

- Emitter follower configuration: the impedance adaption; the minimum current needed for the operation; polarization of the circuit; the current source; the push-pull circuit

- Common emitter configuration: the amplifier and its impedances

- From the ideal transistor to the real one: the Ebers-Moll model and the transconductance concept

- The emitter follower and the common emitter revisited using Ebers-Moll

- The grounded emitter transistor and the possible biasing schemes

- Current mirrors and differential amplifiers

- The Miller effect

OP-AMPS

- A look inside opamps considering all the elements defined in the previous steps and the golden rules to describe their operation

- Negative feedback: the reasons to reduce gain and the definition of the de-sensitivity factor to improve the opamp performance, considering gain, input and output impedance

- Standard circuits: inverting and non inverting amplifier, follower, current source, current-voltage converter, differential amplifier, adder, active rectifier

- Real vs ideal opamps: how real features change opamps behaviour and how we can understand it from Bode plots

- Example of complex circuits: the logarithmic amplifier, the active peak detector, the sample and hold circuit, integrators and differentiators

- Comparators: the standard circuit and the use of positive feedback to obtain a circuit able to work even in presence of noise (hysteresis)

- Techniques of frequency compensation in opamps to avoid instability

- Active filters: filters features; Negative Impedance Circuits and gyrators to simulate inductors; Sallen & Key filters.

BASICS OF DIGITAL ELECTRONICS

- Analog vs digital: from frontend to readout electronics

- Combinatorial logic: gates, three-state and open-collector devices, De Morgan’s theorem, examples of circuits (mux, demux, adder)

- Sequential logic: latch, master-slave flip-flop, JK flip-flop, examples of circuits (asynchronous and synchronous counters, shift registers, parallel to serial converters and viceversa)

- DACs and ADCs: from digital to analog and viceversa

- Basis of VHDL language to implement the circuits in FPGA-based development systems

The course is organized in lectures, each one divided into two parts:

- in the first part the teacher presents the topic, making calculations and describing the behaviour of the different electronic components and the way they have to be put together to obtain the desired results

- in the second part, students are asked to:

** for the analog electronics part of the course - simulate the behaviour of the circuits analyzed in the first part with the SPICE simulation tool, in order to understand the limits of real circuits and how to improve their performance. The simulation tool is free and will be installed on the students’ portable PC in order to work directly in the classroom. For the most representative circuits (for instance: shapers, differential amplifiers, circuits to evaluate the Miller effect, current mirrors, discriminators), students will be asked to assemble the circuit itself and take data to compare them with the simulation results. The assembly will be performed in the classroom in small groups (if possible) and results will be discussed all together at the end of the data taking.

** for the digital electronics part of the course - simulate the behaviour of the circuit with Modelsim and implement the circuits using FPGA-based development systems. The software tools are free and will be installed on the student’s portable PC. Each student will be equipped with a development system in order to implement the simulated circuits and test their behaviour. All the steps will be discussed with all the class during the implementation.

The final examination is an oral one; the student will be presented with a randomly selected list of 4 topics treated during the course. He/she will choose one of the four topics and give a lesson on the topic itself. This part of the exam intends to verify :

- the knowledge of a specific topic in electronics

- the capability of analyzing the component features and behaviour in the time and frequency domains and the limitations one can expect using a real and not ideal component

- the correct use of the technical language needed to explain electronic circuits.

In the second part of the exam, the teacher will start from the topic of the first part to ask questions concerning all the items treated during the course. This second part will allow the teacher to check:

- the level of the knowledge acquired by the student in the different topics of the course

- his/her skills in applying what learnt in a real data taking chain (for instance, in the design of the frontend and readout chain of a real detector)

- his/her capability in choosing the correct component given the boundary conditions (such as: data taking speed, signal to noise ratio, cost).

To pass the exam, the student has to present the topic chosen in the first part in a satisfactory way, with an adequate language, demonstrating a satisfactory comprehension of the features of a component and of the limits of its applications.

To successfully pass the exam, the student should know all the topics treated in the course.

Full marks with laude are assigned to students that accomplish completely what described above, demonstrating to be able to re-elaborate concepts, define applications, describe pros and cons of a choice for a given application, design solutions once being given the boundary requirements of the application itself.

The following texts are used during the course:

- P. Horowitz, W. Hill, ISBN-10: 9780521809269

- J. Millman, ISBN 0-07-042327-X

- slides of the lessons and articles provided by the teacher

For questions/discussion/comments, students are invited to contact the teacher via email at the following address: michela.prest@uninsubria.it

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