Source: https://mokxi.com/learn/path/signals-and-filters Updated: 2026-11-11 All paths # AC, signals and filters Advanced, after Transistors and op-amps for real: sine, peak and RMS, reading a scope, RC and RL filters, frequency response, RLC resonance and active filters. Free 7 lessons 4 h 3 chapters 2,422 XP Electrical · Advanced +250 XP 0 of 7 done Start the course free Sine, peak and RMS Lesson plan for teachers What you will build ## 3 projects, built step by step 7 lessons in 3 chapters, about 4 hours on a simulated breadboard. Free, in your browser, every step checked by the simulator. Chapter 1 project ### Reading a scope The waveform lab: an Uno makes sine, triangle, sawtooth and square waves with PWM and an RC filter. Volts per division, time per division, period and frequency, checked with a frequency counter. Open it in the simulator Chapter 2 project ### Frequency response Two RC filters in a row with a meter after each: gain as a ratio and in decibels, the corner, and a slope that doubles to -40 dB per decade. How to read a Bode plot without needing one. Open it in the simulator Chapter 3 project ### Active filters An op-amp low pass on one 5 V rail: a gain of ten in the passband, a corner set by Rf and Cf, moved down a decade with one capacitor, and the trade between gain and corner. Open it in the simulator The map ## Chapter by chapter Each lesson opens when the one before it is done, and each chapter ends in a project. Chapter 1 ## AC signals What a sine really measures, and how to read one on a scope. Open 265 XP ### Sine, peak and RMS Mains through a 12-0-12 V transformer into a rectifier: what 230 V means when the peak is 325 V, why a 13 V winding charges a capacitor to 17 V, and what happens on the wrong mains. 0 of 6 steps Start What is in it Project Locked 530 XP ### Reading a scope The waveform lab: an Uno makes sine, triangle, sawtooth and square waves with PWM and an RC filter. Volts per division, time per division, period and frequency, checked with a frequency counter. 0 of 6 steps Chapter 2 ## Filters Low pass, high pass and band pass, and how to read a frequency response. Locked 265 XP ### RC low-pass A resistor and a capacitor with a meter on each side: full signal at 100 Hz, 0.707 at the 995 Hz corner, a tenth a decade above it, and the corner moved with one capacitor. 0 of 6 steps Locked 227 XP ### High-pass and band-pass An inductor and a resistor with a meter across each: the inductor’s side passes highs, the resistor’s side passes lows, both read 1.0 V at the corner, and two filters in a row make a band. 0 of 5 steps Project Locked 454 XP ### Frequency response Two RC filters in a row with a meter after each: gain as a ratio and in decibels, the corner, and a slope that doubles to -40 dB per decade. How to read a Bode plot without needing one. 0 of 5 steps Chapter 3 ## Tuned and active Resonance with an inductor and a capacitor, and filters with gain. Locked 227 XP ### RLC resonance A resistor, an inductor and a capacitor tuned to about 1 kHz: the capacitor rings to four times the input at resonance, falls away either side, retunes with one part and sharpens as the resistance drops. 0 of 5 steps Project Locked 454 XP ### Active filters An op-amp low pass on one 5 V rail: a gain of ten in the passband, a corner set by Rf and Cf, moved down a decade with one capacitor, and the trade between gain and corner. 0 of 5 steps Syllabus ## Every lesson in the course All 7 lessons, in order, each with what it covers. Any of them opens in the editor right away. Chapter 1 ### AC signals - Sine, peak and RMS Mains through a 12-0-12 V transformer into a rectifier: what 230 V means when the peak is 325 V, why a 13 V winding charges a capacitor to 17 V, and what happens on the wrong mains. - Reading a scope The waveform lab: an Uno makes sine, triangle, sawtooth and square waves with PWM and an RC filter. Volts per division, time per division, period and frequency, checked with a frequency counter. Chapter 2 ### Filters - RC low-pass A resistor and a capacitor with a meter on each side: full signal at 100 Hz, 0.707 at the 995 Hz corner, a tenth a decade above it, and the corner moved with one capacitor. - High-pass and band-pass An inductor and a resistor with a meter across each: the inductor’s side passes highs, the resistor’s side passes lows, both read 1.0 V at the corner, and two filters in a row make a band. - Frequency response Two RC filters in a row with a meter after each: gain as a ratio and in decibels, the corner, and a slope that doubles to -40 dB per decade. How to read a Bode plot without needing one. Chapter 3 ### Tuned and active - RLC resonance A resistor, an inductor and a capacitor tuned to about 1 kHz: the capacitor rings to four times the input at resonance, falls away either side, retunes with one part and sharpens as the resistance drops. - Active filters An op-amp low pass on one 5 V rail: a gain of ten in the passband, a corner set by Rf and Cf, moved down a decade with one capacitor, and the trade between gain and corner. Keep going ## The next course on your track AC, signals and filters is part of the electrical track, a ladder of courses from zero to expert. Next course ### From gates to a computer Start with one NAND gate, package every circuit you build into a chip, and use your chips to build the next one: an adder, memory, a CPU of your own, and a computer that runs your program. Open the next course Track ### Electrical track Current and voltage you can see, then transistors, op-amps, filters, power and PCBs. Every circuit runs in a real circuit simulator in your browser. See every course on the track Kits ## Build it on your bench too Every lesson runs in the simulator with nothing to buy. When you want the real thing, these kits have the parts. Have a kit already? ### Find your kit Pick the starter kit you own and run every lesson in its manual with the same parts on the same pins. See every kit Questions ## About AC, signals and filters Is AC, signals and filters free? Yes. All 7 lessons of AC, signals and filters are free and run in your browser, with nothing to install and no parts to buy before you start. Do I need any parts? No. Every circuit is built on a simulated breadboard, and the simulator checks each step as you go. When you want to build it for real, the same parts and wiring work on a real bench. How long does AC, signals and filters take? About 4 hours: 7 lessons in 3 chapters, each one a few short steps. Your progress is kept, so you can stop after any lesson and pick up where you left off. What will I build? Each chapter ends in a project that puts it together: Reading a scope, Frequency response and Active filters. Where do I start? With "Sine, peak and RMS", and each lesson builds on the one before it. New to circuits? Electronics basics is the course that starts from zero.