Please read the description/textbox first. Circuit of a very usable test oscillator with a TL 071 Opamp that can give out square waves and triangle waves (read: kind of sawtooth waves).
It can go to max. 131 KC with triangle/sawtooth waves, in the frequency band higher than 50 KC.
For Cx (the frequency dependent capacitor, responsible for the frequency band where the circuit can be used, in combination with the 100 K freq. setting potentiometer) you can use 100 pF (highest frequencies) or 10000 pF (=10 N) for the lower frequencies. Medium frequencies: 470 pF (try/test).
The frequencies and possible waveforms are showed in the video. Not showed is how the circuit works with a 100 N (=0,1 uF) non-polar capacitor as “Cx”.
It will go in that case to very low frequencies (200 Hertz-1 KHz), I tested it that way, though the waveform is (could be) not pure or pure enough, though also not pure waveforms can be usable in certain electronic circuits. So do that experiment yourself, say on a breadboard. Look at the oscilloscope and study the waveforms. Assess whether these waveforms are usable for your electronic application.
The TL071 is a versatile high quality Opamp with an extremely high input impedance, because it has a FET (Field Effect Transistor) at its input, thus where it “receives” signals of whatever kind.
Could be tiny voltages or tiny currents, in the latter case usable as a high current amplifier that can amplify tiny changes in currents at its input. More in the TL 071 datasheet, everywhere available on the www.
First experiment and test with this TL 071 is here:
https://youtu.be/Tb5A_mw1DRI
That is an old video from 9 December 2019, but it gives a quite good analysis of what this TL 071 Opamp chip can bring when used in a oscillator circuit.
It gives the basic information and a good reason to test it on a development board.
The 2 schematics showed now (16 august 2022) are an elaboration of that first TL 071 test circuit.
All circuits work properly, by the way. The oscillation setting (via the 100 K potentiometer) is somewhat critical (oscillation can stop sometimes) but you can bring the oscillation “in the band” by precise aligning of the 5K1 trimmer that is in series with it (goes to pin 6 of the TL071).
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I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube. Search there, and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, etc. Some persons try to find gold via my circuits. I take distance from all these fake claims. I cannot help that these things happen. Upload 16 August 2022.