Please read the description first. This video is an elaboration of an earlier circuit that I published on RU-vid: a 1960’s Multivibrator, that can work up to (say, ideally) 2 MC, made with a constant current source and only 4 transistors.
Link is here (19 August 2024)
• Very good Muvib square...
I found this circuit very interesting and, at the same time, simple & easy. Thus ideal to elaborate it to a hobby circuit (waveform generator, how that works out in practice is showed in the video). It all gave me (thus) a reason for elaborating this 1960’s circuit.
The most interesting eleboration that I did was (perhaps): taking away the constant current source and replace the fixed value resistors out of the original schematic by potentiometers of 4K7 and 470 Ohm.
That means, of course, that you (can) get a bigger “bandwidth” (in terms of frequency) and waveforms with other time relations. Of course with the risk that the Multivibrator switches “off” when it is out of its “oscillation zone”. And that surely happens….(video).....
But no problem: I added a blue LED indicator that shows when oscillations occur, or not. So, even without an oscilloscope, you can see whether the circuit oscillates or not. The “blue LED lighting” is aligned/set via a 1 M potmeter in the schematic (video).
Important things to know in this video:
1. On 1.38: the (-) lead where the 2 resistors of 4K7 are going to is now, in the new circuit, connected to ground, minus, mass
2. On 1.38: The 4K7 fixed value resistors in the emitter leads were changed into 4K7 potmeters each with a protective resistor of 200 Ohm (or 220 Ohm) to the (-).
3. Value of the caps: between 150 uF (5 Hz-22 Hz, very distorted square waveform) and 500 pF or 800 pF (say 1.8 MC triangle wave). Via a rotary switch with 11 positions
4. The grounded base buffer stage showed here with its extremely low input impedance (resistance) helps to keep the waveform out of the MUVIB undistorted
5. On 2.53 in the video I tell that the protective resistor is 1 K (1000 Ohm) but that is not correct, it is 200 Ohm or 220 Ohm (idem in point 2).
6. On 2.51 of course I am talking about (now) potentiometers of 470 Ohm, not about fixed value resistors
7. Surely good squarewaves (with a better duty cycle, say in the oprder of 30 % to 40 %) can be set from 500 Hertz up to to (say) 800 KC. I did not have enough time to show that now in this video. it is say precision alignment of 4 potmeters + the bias + the amplification in the G-E Stage. So: do your own experiments, always interesting!
NB: the "GROUNDED BASE" transistor circuit is explained here • The Grounded Base 1 tr...
On HF and VHF there is often a coil of X windings in the emitter lead of the so called "grounded base" transistor circuit. In the above named video it is a resistor of 2000 Ohms, also a low resistance/impedance that does the job. More info in that video.
The (say) perhaps interesting thing in this video is the buffer stage (Grounded Base), followed by a grounded Emitter Stage that does the job of amplifying. I used BC 547b NPN Si transistors “all the way” because of their good properties, up to (say) 9 MC.
Grounded base 1 transistor buffer stage (more info) • The Grounded Base 1 tr...
My You Tube channel trailer is here: • Radiofun232 on RU-vid...
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.
More info in this video • Find and search Electr...
So before asking questions it could be an idea to look there. Of course I like to communicate, that is one of the RU-vid’s principles that I hold on to, since 15 years ago. So don't hesitate to ask questions about my circuits and what I am doing on RU-vid, publishing all these videos. I am always interested.
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 RU-vid.
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 6 September 2024.
To give ideas for the vakue of CX in the schematic:
1 uF=560 - 700 Hertz range
0,1 uF (100N) = 5-6 KC range
0,01 uf (10N) = 50 KC range
1 N (1000 pF) = 480 KC range
470 pF = 1 MC range
smaller than 470 pF = higher than 1 MC range
16 сен 2024
