Introduction to first order filters

This course introduces the foundational concepts of RC and RL filters, empowering you to understand, design, and analyze these essential circuits. You will explore how these filters control and shape electrical signals through low-pass and high-pass configurations, and learn how to determine critical parameters such as cutoff frequency and phase shift. The course also covers real-world applications of these filters, from audio tone shaping and noise removal to sensor signal conditioning and switch debouncing.

The course structure combines short, focused video lectures, clear explanations, and practical activities that build your knowledge progressively. Throughout, you will engage in simulation-based exercises and breadboard experiments, applying your understanding to real-life situations. Key activities include calculating filter responses at various frequencies, visualizing behavior with Bode plots and phasors, and examining how cascading filters can improve performance.

To support your learning, you will use Python, CircuitLab, and the Analog Discovery 3 for simulations and practical measurements. If you do not have this hardware, you can still follow along with the demonstrations and Python exercises, using online simulators or your own measurement tools. Downloadable resources and exercises ensure you can apply what you learn immediately, gaining practical skills in designing and analysing RC and RL filters.

Who is this course for?

This course is designed for electronics enthusiasts, hobbyists, and students who already have a solid foundation in basic electronics concepts, such as Ohm’s Law, voltage division, and working with simple circuits. If you have completed my Introduction to Electronics course or have equivalent experience, you are well-prepared to dive into RC and RL filters and expand your understanding of how these essential building blocks shape and control electrical signals.

Whether you’re looking to reinforce your skills with practical, hands-on experiments or you want to explore real-world applications like audio shaping, sensor conditioning, and noise filtering, this course will guide you step by step. It is an ideal next step for learners who want to bridge the gap between theory and practice, and build confidence in analysing and designing first-order RC and RL filter circuits.

Hardware & Software

This course uses a combination of simulation, data analysis, and circuit design tools to support your learning and experiments.

Python

Python is used throughout the course for data analysis, visualisation, and calculation of filter responses. If you do not have Python installed, you can download it from the official Python website. The course includes a primer on essential Python skills, and uses the following libraries:

• NumPy for numerical calculations and managing arrays.

• Matplotlib for creating plots and visualising data

Simulators

The course demonstrates filter behaviour using online circuit simulators that make it easy to build and analyse circuits:

• CircuitLab is an intuitive online simulator that allows you to create and analyse circuits, measure filter responses, and experiment with circuit designs.

• Tinkercad Circuits is another accessible, web-based tool that lets you build and simulate circuits interactively. It’s ideal for beginners and can be used for exploring basic RC and RL filter behaviour.

WaveForms (for Analog Discovery 3 users)

If you have the Analog Discovery 3 device, you can use the WaveForms software to generate signals, measure filter responses, and capture data. This powerful tool integrates an oscilloscope, waveform generator, spectrum analyser, and other instruments, making it ideal for hands-on experimentation.

The course includes detailed instructions and resources to help you set up and use these software tools, even if you are new to them. If you prefer to work with other simulation tools, you can still follow the principles and adapt the examples to your preferred environment.

Hardware

The practical activities in this course are designed to be accessible and flexible, using commonly available electronic components. Aside from a mini-breadboard, you will need the following:

Resistors

A range of resistor values will be useful for constructing RC and RL filters, typically:

• 1 kΩ to 100 kΩ for standard filter configurations

• Adjustable resistors (potentiometers) can be used for experiments requiring variable resistance.

Capacitor

Common capacitor values include:

• 100 nF to 10 µF for typical RC filter applications

• Ceramic or electrolytic capacitors are both acceptable, depending on the experiment.

Inductors

For RL filter activities, suitable inductors typically range from:

• 1 mH to 100 mH

• Values depend on the desired cutoff frequency and practical considerations in your circuits.

Breadboard and jumper wires

A breadboard and jumper wires will allow you to build and test your circuits without soldering.

Oscilloscope (optional)

An oscilloscope helps to visualise filter responses in the time domain, but if you do not have one, you can follow along with the demonstrations and simulations in the course.

Signal generator (optional)

A standalone signal generator can be a useful tool for testing filter performance with different input waveforms. If you do not have a signal generator, the Analog Discovery 3 or your computer’s audio output (for audio-range signals) can serve as alternatives.

Analog Discovery 3 (optional)

The Analog Discovery 3 is a powerful, all-in-one instrument that can function as a signal generator, oscilloscope, and spectrum analyser. It’s highly recommended for deeper experiments in filter response and real-world circuit behaviour.

If you do not have access to the optional hardware, you can still complete all simulation-based activities and follow along with demonstrations for the hands-on experiments. The course is designed to be accessible and practical, regardless of the hardware you have on hand.