I delivered a series of lectures on electronic instrumentation to third-year Biomedical Engineering undergraduates at the University of Moratuwa, centred on a question every biomedical measurement system faces: how do you recover a microvolt-level signal from a noisy, interference-filled world? The series builds from the fundamentals of noise, through transistor and op-amp noise models and the physics of interference, to PCB layout and a complete ECG front-end design. Each lecture below has a written summary — key equations, worked examples and diagrams — and the full slides as a PDF.
7 lectures · 264 slides in total
The toolkit for everything that follows: representing noise sources in a circuit, quantifying them, knowing when they can be added, propagating them through a filter, and comparing a system against a reference with the noise figure.
A working, quantitative picture of where random noise in an instrumentation circuit comes from, classified by the physical mechanism that produces it, and how to combine the sources correctly.
Turns the noise toolkit into transistor-level models: small-signal models for the diode and BJT, their noise sources, and how to refer them to the input. The key lesson is that a two-port needs both a voltage and a current noise source, and that these can be correlated.
Replaces transistor-level detail with the standard three-source op-amp noise model, then works a full inverting-amplifier example and shows how source resistance decides which noise term dominates — and therefore which amplifier to choose.
The longest lecture of the series: everything about interference that enters from outside the circuit. Each coupling mechanism is modelled quantitatively, paired with its mitigation, and the lecture closes with power-line filters, data-acquisition noise and ADC quantisation noise.
Turns the interference theory of Part 5 into layout rules, then applies it to a graded group assignment: a battery-powered wearable ECG board, with a worked rationale for its power tree, ADC choice and reference voltage.
A start-to-finish case study: how 50 Hz mains reaches an ECG through capacitive coupling, why each effect appears as common-mode or differential interference, and how the instrumentation amplifier and driven-right-leg circuit tackle them.
Slides are PDF exports of the original PowerPoint decks.