Electronics Lab - 2: Analog Electronics
Prerequisites for this lab
- Electronics Lab - 1 (EP215, Physics department course)
- Basics of passive components: R, L, C.
- Basics of transistors. Either BJT or FET is fine: the experiments can be performed with either of them.
- Some theoretical familiarity with opamps - developed in detail through hands-on experiments in this lab.
Syllabus
This laboratory syllabus is primarily built around opamps and their applications. It is expected that discrete circuits will be completed in the earlier Electronics Lab - 1. Highlights of the syllabus are:
- Build an opamp with discrete components = differential amplifier at input + output stage. The main point is that opamps have close to infinite input impedance.
- Introduction to opamp as a monolithic IC (LM741 typically used):
- Offset nulling and bias current.
- Unity gain inverting and non-inverting amplifier.
- Gain Bandwidth Product of opamp as a design limitation.
- Opamp applications with feedback. Typical applications include:
- Active filter, differentiator, integrator
- Schmitt trigger (positive feedback and hysteresis)
- General Barkhausen criterion for oscillation in any feedback circuit
- Oscillators: Astable multivibrator , Wein bridge oscillator
- Instrumentation amplifier: 3 opamp implementation with minimal requirement of matching passive component values.
- Lockin amplifier: measure small analog signal at specific frequencies in the presence of noise
- IC555 and its many uses (transition to digital electronics in Electronics Lab 3): Typical uses: pulse width modulation, counter etc
In parallel (starting around Lab 4 : introduce SPICE and/or gEDA simulation tools for modeling circuit behaviour. Note that the instrumentation amplifier and lockin amplifier experiments typically require multiple sessions.
Representative experiments
Note: The assignments are set up in modular form. Students fill out answers in the provided space.
Marks are alloted by the teaching assistants as they complete each module. At the end of the session the students submit
the completed assignment and the marks are entered into a spreadsheet by the lab staff. There is no journal writing/correction required.
Close to the end-semester exam, the solved assignments are put up on Moodle for students to revise.
There is an element of surprise as the students don't know the exact problem they will work on when they arrive for a lab session.
They are given a review of the concepts involved in the preceding lecture. Hence it is important to co-ordinate the timetable such
that the lecture session occurs a few days before the lab session.
Discussion among the members of each group is encouraged during the lab session. The teaching assistants are required
to invigilate such discussions and mark the completed work based on the perceived contribution of the student to the group's work.
You are free to add new components to the experiments or suggest new experiments. When editing these assignment sheets, it
is suggested that you use MS Word 2010 on MS Windows. Unfortunately using other word processors or other OS
(Linux LibreOffice, MacOS Word etc) causes unwanted changes in the alignment of figures in the page layout.
Hence system agnostic PDF files are also provided.
| No. | Experiment | DOCX | |
|---|---|---|---|
| 1 | Introduction to Opamps | P | P |
| 2 | Positive feedback in opamp circuits | P | P |
| 3 | Negative feedback in opamp circuits | P, S | P, S |
| 4 | Active filters and phase shifts | P, S | P, S |
| 5 |
Opamp imperfections - input bias current and voltage offsets
Note that this lab also implicitly employs current to voltage conversion (transconductance) to measure I_bias. This should be highlighted in the accompanying lecture |
P, S | P, S |
| 6 | Instrumentation amplifier (*notes from Nitin Pawar) | P, S | P, S |
| 6a | Instrumentation amplifier application - measure milliOhm resistance changes in a strain gauge. | docx | S |
| 7 | Power transfer. Impedance and reflections in coaxial cables. | P, S | P, S |
| 8 | Relaxation oscillator | P, S_1, S_2 | P, S_1, S_2 |
| 9 | Lock-in amplifier (requires two sessions) | P_A, S_A, P_B, S_B | P_A, S_A, P_B, S_B |
| 10 | IC555. Its application as a monostable pulse generator, astable multivibrator. | docx | S |
Lecture notes
The lectures must be focused on the content of the experiments you plan to proceed with during the semester. This a collection of lecture notes used to highlight some of the core concepts.
| No. | Title | pptx | |
|---|---|---|---|
| 1 | Lab review, plan | pptx | |
| 2 | Positive Feedback | pptx | |
| 3 | Negative Feedback | pptx | |
| 4 | Analysis of feedback | pptx | |
| 5 | Opamp imperfections - Vos and Ibias | pptx | |
| 6 | Instrumentation amplifier review | pptx | |
| 7 | Impedance and power transfer | pptx | |
| 8 | Cable impedances - review | pptx | |
| 9 | Theory of lockin amplifiers | docx |
Exam assignments
This is a collection of exam assignments given in the course over the last few years. Due to space constraints, the exam must be
conducted in two or more sessions so that each student is able to complete the assignment individually. Early on in the course, it must be
stressed that while the students work in groups and learn from each other during the semester, they must appear for the endsem exam
individually. This motivates them to learn all aspects in each lab assignment - problem solving, circuit design and
breadboard circuit building.
The exam assignments listed here are in pairs [A,B] - each pair of assignments are of approximately equal difficulty level, so that they can
be administered to two halves of the same class.
| No. | Title | docx | |
|---|---|---|---|
| 1 | (Spring 2014) EndSem A: Class D switching amplifier | docx | |
| 2 | (Spring 2014) EndSem B: Zero crossing detector | docx |
Contact:
Room 130,
Department of Physics,
IIT Bombay
Powai, Mumbai 400 076
Tel: +91-22-25764590
Lab staff:
Nitin Pawar
nitinpawar[at]iitb.ac.in
Swapnali Gharat
swapnalig[at]iitb.ac.in
Snehal Narvekar
narvesnehal[at]gmail.com
Lab-Incharge:
Pradeep Sarin