In my new course, “Introduction to Electronics: Filters,” I guide you through the essential concepts and hands-on experiments that make filters such a fundamental topic in electronics. In this post, I give you a preview of one of the lectures in the course: “Impulse Response in First Order Filters.” This lecture helps you see how first-order filters react to a sudden, sharp input—an impulse—and how this response reveals the filter’s core characteristics.
What is impulse response?
In the lecture, I focus on the impulse response of first-order filters, both low-pass and high-pass. The impulse response is the output of a system when presented with a very short, high-amplitude input signal—mathematically, an ideal impulse. In practical terms, it’s like striking a bell and listening to how it rings. The way a filter responds to this “strike” tells you a lot about its internal workings and its effect on signals.
Understanding the impulse response helps form the foundation for analysing and predicting how filters behave with any input. In signal processing, the impulse response and the filter’s transfer function are two sides of the same coin. If you know one, you can derive the other. This is why, in the course, I dedicate time to exploring the impulse response in detail, using both theoretical analysis and practical demonstrations.
Key concepts explained in the lecture
In this lecture, I start by explaining what an impulse is in the context of electronics. An ideal impulse is a mathematical abstraction: it has infinite amplitude and zero duration, but its area (the integral) is one. In real circuits, we approximate an impulse with a very short, high-amplitude pulse. I show you how to generate such a pulse using a function generator and how to apply it to a first-order filter circuit.
You learn how the impulse response of a first-order low-pass filter is an exponentially decaying function. This means that, after the impulse, the output voltage drops rapidly at first and then more slowly, following a curve described by the filter’s time constant. I demonstrate this with a practical experiment, using an oscilloscope to capture and analyze the output waveform. You see the theory come to life as the oscilloscope trace matches the expected exponential decay.
For the high-pass filter, the impulse response is different: it’s a sharp spike followed by a rapid return to zero. This behavior reflects the high-pass filter’s tendency to block low-frequency signals (including DC) and pass rapid changes. Again, I use real measurements to show you exactly what happens, reinforcing the connection between mathematical models and physical circuits.
In the lecture, I also discuss the time constant, which is determined by the resistor and capacitor values in the filter. The time constant controls how quickly the output decays in a low-pass filter or how quickly it returns to zero in a high-pass filter. By adjusting these values, you can shape the filter’s response to suit your needs.
How this lecture fits into the course
This lecture is part of a carefully structured journey through the world of filters. Earlier in the course, you learn about the basic concepts of resistance, capacitance, inductance, and the behavior of RC and RL circuits. You build and test simple low-pass and high-pass filters, exploring their frequency response and step response. By the time you reach the impulse response lecture, you have the background needed to appreciate why the impulse response is so important and how it connects to everything you’ve learned so far.
The course doesn’t stop at theory. I guide you through hands-on experiments using affordable tools like the Analog Discovery 3 and open-source software such as Python and CircuitLab. You get to simulate circuits, analyze data, and see how the math translates into real-world signals. This practical approach helps you develop intuition and confidence, whether you’re a student, hobbyist, or professional looking to refresh your knowledge.
Related posts and course Insights
If you’re interested in diving deeper into the world of filters, I invite you to read two related posts that provide additional context and hands-on insights:
- Exploring RC High-Pass Filters: A Practical Experiment with Analog Discovery 3: This post walks you through a real experiment with a high-pass filter, showing you how to set up the circuit, take measurements, and interpret the results. It’s a great companion to the course, especially if you enjoy learning by doing.
- Upcoming course: Learn first-order filters with Python, simulation, and live experimentation: Here, I discuss the philosophy behind the course and how you can use modern tools to bridge the gap between simulation and real-world experimentation. This post gives you a sense of what to expect and how the course can help you master filters from multiple angles.
Both posts are designed to complement the course and help you get the most out of your learning experience. I encourage you to check them out and see how they fit into your journey as an electronics explorer.
What else will you discover in the course?
“Introduction to Electronics: Filters” is packed with lectures that build your understanding step by step. After mastering the impulse response, you’ll move on to topics like frequency response, Bode plots, and the design of more complex filters. Each lecture combines clear explanations, practical demonstrations, and opportunities for you to experiment and ask questions.
I’m planning to publish this course in the next week or so. I hope that this preview has opened your appetite to learn about first order filters!