This textbox/description relates to 2 video’s:
Video 1: the “wave-shaper” circuit that can change sine waves into kind of square waves (kind of? watch the video), made with only 3 (10 cents) transistors, all of them the BC 547 b.
General purpose NPN transistors with a HFE (Bèta) of 300 or 250. I cannot give more explanations, all is explained in the video.
Works (translates sine to square wave) between 200 KC and 700 KC, was tested in that frequency band. Surely can probably work on lower frequencies (lower than 200 KC) surely not (!) on higher frequencies. Above 700 KC: too much waveform deterioration, it was tested, this setup is too simple for that. But feel free and try/experiment (!). The square waves generated by this pulse former have somewhat "rounded edges" in the mentioned frequency band, anyway: could be a useful & simple circuit when experimenting with radio circuits, HF transistor or Opamp drivers, etc.
Video 2: a "frog sound" oscillator made with three medium power transistors. 2 X the BD 139 NPN Silicon transistor (Hfe/Bèta = say 70-150) and 1 X the BD 140 PNP Silicon transistor (Hfe/Bèta also between 70 and 150).
Cx (here 56 N = 0,056 uF non polar) sets the “insect sound or frog sound” frequency, watch the video for the oscilloscope views how such a strange sound looks like (many small voltage peaks).
The 220K (or 250 K) potentiometer also sets the frequency (band) where it works.
The circuit is EXTREMELY SENSITIVE TO LIGHT, even on tiny amounts of light (of whatever source: the sun, lamps) it starts to “”beep”. Can be used to repell? I don’t know.
Link to the frog/insect sound generator is here https://youtu.be/ESJBrr4C08w
Link to the TL 071 FET Opamp function generator circuit (max 200 KC) discussed in this video is here https://youtu.be/FXAKKvH9FrE
My You Tube channel trailer is here: https://youtu.be/xbgQ8T3oqh4 When you search, search always “NEWEST FIRST” to get the right overview. You can also search via the “looking glass” on my Channel trailer via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in.
My books about electronics & analog radio technology are available via the website of "LULU”, search for author “Ko Tilman” there.
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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 17 August 2022.