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.
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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.
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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.
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 simulatorActive 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 simulatorThe 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.
- Open265 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.
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- ProjectLocked530 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.
- Locked265 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.
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- Locked227 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
- ProjectLocked454 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.
- Locked227 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
- ProjectLocked454 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.
AC signals
- Sine, peak and RMSMains 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 scopeThe 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.
Filters
- RC low-passA 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-passAn 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 responseTwo 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.
Tuned and active
- RLC resonanceA 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 filtersAn 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.
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 courseElectrical 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 trackKits
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.
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 kitQuestions
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.