Astabile Multivibrator with FETS, not ideal, 30 Hz-12 KC schematic and demo, fun for experiments
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- Опубліковано 12 вер 2024
- Please read the description first. Circuit of a Astabile Multivibrator that can work between 30 Hertz and 12 KC. Correction: the pin connections in the drawing and the thumbnail are not (!) OK... Also in practice I reversed Drain and Source. Though it worked. Also strange. Perhaps that was the reason of the poor functioning. Thanks @kd5ozy !
Re-tested it on 23 June 2024: it works in both cases, whether Drain and Source are reversed, or not. In both cases with the same issues.
Making such a circuit with FETS is not (!….) easy. I did quite a few experiments to finally find this circuit that works (somewhat, but in my opinion not ideal, given the low frequency range, max. 12 KC, and its critical supply voltage). Perhaps important: I used MOSFETS, they have often or in general a quite high capacitance at their Gates, if so that will limit the maximum frequency that could be reached. Could be a reason...
With BJT transistors such a circuit (Astable Muvib) has a high success factor, say 80 -90 % or so.
Say it “always” wants to work, with 2 BJT transistors, 2 caps and 4 resistors.
Many circuits with that setup are on my YT Channel. You can find them via the “looking glass” (= search option) on my Channel Trailer, “Radiofun232 on UA-cam”. Type there searchwords like “multivibrator” or “Astable” or “A Stabile multivibrator.
With BJT transistors this circuit can work on a broad range of voltages, going from (say) 0,8 Volt to 24 Volt or even higher.
With this FET circuit that is not (!) the case, the voltage where it wants to work is very critical (bandwith of 1,5 Volt) and it also depends (as far as I could see) somewhat on the generated frequency.
Combined with the critical setting of the second 470 K potentiometer in the circuit, anyway.
The frequency where it works is set by the 2 capacitors. Their values set the frequency band where it works. The duty cycle can be set via (different or the same) values of these capacitors.
The duty cycle also depends on the setting of the second 470 K potentiometer, thus the one going to the second IRF 830 FET.
With 2 X the BF 256 A (small signal N-FET) it did not work, but with 1 X BF 256 A (as first transistor) and 1 X IRF 830 (as second transistor) it worked.
Room for many experiments and many hours of fun! To get this circuit to work better and/or adapt it to your personal needs and idea’s for a certain electronic application!
Better and easier Astabile Muvib oscillators made with normal transistors (BJT circuits) can be found via the Channel Trailer on my YT Channel.
My You Tube channel trailer is here: • Radiofun232 on UA-cam...
When you search, search always “NEWEST FIRST” to get the right overview.
You can (thus) search via the “looking glass” on my Channel trailer. Alsof or electronic circuits )audio & radio & test equipment). Via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; thus 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. www.lulu.com/s....
I keep all my YT videos constant actual, so the original video’s with the most recent information are always on UA-cam. 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. Upload 22 June 2024.
gate drain source. Not gate source drain pinout
You are right. I must have reversed the Drain and Source, but it worked that way. Very strange, I am going to make it again with the right pin connections. I will pin your comment. I re-tested the circuit today and it also works when Drain and Source are not reversed. With the same issues, by the way. Thanks again. 23 June 2024.
@@radiofun232 'FETs' will work 'sometimes' reversed?
@@RobbyMatthias Yes, true. I tested it today and it works also (and with the same issues) when Drain and Source are not reversed.
When you want to search for many very good working Astabile multivibrator circuits, the "search word" on my YT Channel Trailer (Radiofun232 on UA-cam) is "multivibrator". You can type that in the "looking glass" option = the search option there. 22 June 2024.
I already knew this from reading about the history of radio electronics, however, it's always good to cite a source. This is from Wikipedia if you do a search "In the early days of radio, amateurs nailed bare copper wires or terminal strips to a wooden board (often literally a bread cutting board) and soldered electronic components to them.[1] Sometimes a paper schematic diagram was first glued to the board as a guide to placing terminals, then components and wires were installed over their symbols on the schematic. Using thumbtacks or small nails as mounting posts was also common."
Thanks Barry, it is ideal voor experiments, getting an electronic circuit to work. Finding the values of components out, etc.
@@radiofun232
I know. I was just posting a rebuttal to someone's comment that your electronic boards were not bread boards.
👍Thank you sir.
A surely not very easy circuit, but anyway & thus thanks for your comment. 25 June 2024.
I used an astable multivibrator to control a bilge pump on a duck decoy.
Good use of this circuit!
Thumbs 👍
Thanks, though it was far from ideal.....(anyway).
sir,im currently making non resonant flyback driver so im using astable multivibrator for my oscillator,i use general purpose npn transistors(can work with pnp(tested)) and it can reach frequencies of 100kHz with somewhat variable duty cycle,now im not sure wether or not its stable since i dont have counter,but i can see quite nice(not perfect )square wave.
If so, my idea is that it is OK and it works. When the waveform bibbers on the scope, it is (in general) not stable. But whether precise stability is necessary, it depends on the circuit where you want to use it. When it is non resonant there is a certain play in the stability, though there is in general an optimum frequency where it works at its best. Try to get a counter, it can help a lot. 22 June 2024.
@@radiofun232 thanks alot for insightful response,i use 2n3054 as switching transistor(not optimal but works).It provides nice little plasma without overheating the transistor even without heatsink,anyway video is awesome,you re one of most influential peopole from whom i learn.Thank you.
@@trofaznimotor901 You are welcome, good to hear that (that my video's are/were useful). Anyway, that is a brilliant result with your circuit! Good that it does not suffer from overheating.
grate video , but that is not a bread board :)