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This is a simple circuit using only one IC, a TL084 quad opamp. The integrator integrates the output. When the output is positive the integrator integrates in a negative direction. When its output goes below a selected negative value the output switches to negative. That makes the integrator integrate in a positive direction until its output goes above a selected positive value. That makes the output switch to positive again and the integrator integrates negative again. It does this continuously. Hence the integrator produces a triangle wave. The symmetry is fine-tuned by trimpot R4 which adjusts the midpoint bias of the circuit.

I operate the circuit from +12V. Since this may come from a noisy +12V switching power supply I provide some filtering with R2 and C2.

When I first set it up to measure THD+Noise with ARTA software (http://www.artalabs.hr/ I was getting only 8%. Wrong. Then I saw that I was clipping the triangle wave.

Clipping a triangle wave makes it more sine-like. This is the principal used by the XR2212 and ICL8038 (Intersil) and MAX8038 (Maxim) function generator ICs, only they clip their triangle waves in segments. They were all discontinued years ago. Although you can still buy them from companies in China (through eBay) I suspect that they are counterfeits. (But the ones I bought worked fine.)

As measured by ARTA Audio Measurement and Analysis Software the THD+Noise is 11.93% which is about right for a symmetrical triangle wave. The theoretical value is 12.1%.

The square wave output produces a THD+Noise of 42.98% which is about right for a symmetrical square wave. The theoretical value is 48.3%. Mine is lower probably because the edges are not as sharp as they could be.

Before finding ARTA I had been using a different spectrum analyzer program and I did not believe the results for THD+Noise. I decided to make my own triangle wave with the ability to tweak the symmetry. And I wanted something I could hold in my hands and which would produce an actual signal, not a simulation.

If you are not already a Maker (and you want to be one) see my tutorial on Making Things at www.jmargolin.com/making/jm_making.htm

JM

May 24,2019
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• Omer Faruk Ucar from TURKEY
Founder of the project ‘Lezzetli Robot Tarifleri’ In the frame of this project he produces Turkish contents about electronics/software and serves it to people for free. He produced many jammer devices mostly drone dropper weapons while working in electronic defense industry. He gave lessons to teachers about software and electronics in a program which supported by the government. And now he is working as a hardware engineer on SCADA systems syber security.
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• Ilya from RUSSIAN FEDERATION, THE
Power electronics engineer
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• Inventor of TV-B-Gone, a keychain that turns off TVs in public places. Co-founder of 3ware, a successful Silicon Valley startup in the 1990s. Pioneer of Virtual Reality in the 1980s. Author and teacher. I go around the world giving talks and workshops. Promoter of hackerspaces, open source hardware. Mentor for others wherever I goes. Co-founder of Noisebridge hackerspace in San Francisco. President and CEO of Cornfield Electronics. http://en.wikipedia.org/wiki/Mitch_Altman
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• Catia Diaz from MEXICO
Catia Diaz director of YouTube channel catykanal that was created to insentiate the taste for electronics with tutorials explained in a simple and fun way. Teacher with more than 3 years of experience in promoting the learning of electronics to children and young people.
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• Jiri Praus from CZECH REPUBLIC, THE
I am an artist. I design electronics and brass wire sculptures. www.jiripraus.cz
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• Oyvind Dahl from NORWAY
NOTE: If you have a project that I don't think is for beginners (or I don't understand what it is/lacks documentation) - you'll automatically get a low score from me even though your project is really cool. Sorry! ABOUT: Author of Electronics For Kids. Creator of Ohmify.com and the electronics blog build-electronic-circuits.com.
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• Ever since I was a kid, I love tinkering with anything that involves energy from toys to cellphones. I love designing and creating projects that could be innovative with the use of electronics. I was also appointed team leader of the University of Sto. Tomas team for the Shell Eco-marathon Philippines Competition in 2018.
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• João Duarte from PORTUGAL
http://elab-hackerspace.org/ | http://sandworx.com/
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• J_RPM from SPAIN
My name is José Ramón Pueyo, I live in Spain. For more than 40 years he has worked in the radio communication sector, mainly with RF equipment and developing control and monitoring systems.Five years ago I opened a channel on YouTube (J_RPM) in order to share some developments and divulge technical information.
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• www.cursoderobotica.com
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By igel