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Electronics beginners frequency audio generator with many different waveforms 40 Hz-20 kHz

Electronics beginners frequency generator (audio generator) that can generate frequencies between 40 Hertz and 22 KHz with a minimum of components.
Used transistors (left to right in the schematic): TS1 = BC547 TS2= BC547 TS3=BD139
Waveforms differ very (!!) substantially due to the way that the astabile multivibrator was made: 1) it had to work under all circumstances 2) in a broad frequency band 3) with a minimum amount of components 4) with a differentiator circuit.

So I had to realize the maximum of incongruency between transistor 1 and transistor 2 (Darlington) to fulfill these needs. Watch the oscilloscope views for more info.

When it stops during use, press the “restart” (=start) switch, that disconnects the power supply and starts the multivibrator again.

Only seldom necessary to use that “restart” switch, only when using the differentiator potentiometer the generator sometimes switches off on (say) 20 KHz.

When you do NOT want the generator to stop when you use the “differentiator” switch (S3) and potentiometer (P2) on high frequencies, say 20 KHz, change the 12 Ohm resistor into a resistor of 22 Ohm or 33 Ohm or 47 Ohm or 100 Ohm.

Of course the “differentiator effect” with such a higher value resistor will be less present when turning P2 (1K). Position switch is possible.

By the way: the circuit generates good even squarewaves with identical (..identical) capacitors (transistor 1 – Darlington 2) between 470 N and 22 N. But that was not the aim of this circuit.

Of course: you can buy a perfect frequency generator nowadays 2019 for (say) 10 Euro’s or Dollars in China, say Banggood etc. But doing experiments with this circuit leads to more practical knowledge about electronics.

All the videos hat I have published on You Tube can be found via my Channel Trailer: Link is

In thematic order you can find these video’s under the “comments” section.
Important: to find all the links to the (+/-700) video’s on my YT Channel, select, in the comments section, “NEWEST FIRST”

My books about electronics are available via the website from “Lulu”, search for author “Ko Tilman” there.

https://www.lulu.com/shop/search.ep?keyWords=ko+tilman&type=

There is an important video via which you can buy a document where I give links to many of my video’s, published between 2010 and 2018.

Link is: https://youtu.be/XXRsA24NUE0

My books are also available via Barnes and Noble and via Amazon.

Regarding all my video’s: I constantly keep them actual, so the original video’s with the most recent information are always on YouTube. That is the source, and search there. When my video’s are reproduced or re-edited on other websites/channels you can not (!) be sure about the original content (=really working electronics) and important adaptations to the circuits.

Be aware of that, I saw on the internet my circuits reproduced in a poor or even not proper way. I can not help that, sorry. Upload 3 August 2019.

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Beginners circuit to learn a lot about electronics, especially oscillators (practical schematic)

The a-stabile multivibrator circuit made with 2 x BC 547 b is a very good beginners circuit.
You can learn a lot about: R-C frequency relations, how to generate different frequencies in the most elementary way, how to generate certain waveforms that you need/like by playing with resistor and capacitor values, suplly voltage, time relations, etc etc. Important: could be that it sometimes does not want to start, like YT user Micky Bee mentioned. If it does not want to start oscillating go to https://youtu.be/rmrH4MqvQRo
for more info.
When it does not want to start oscillating change the value of the BASE resistors of TS 1 and TS 2 substantially, say: 1 K and 10 K or 10 K and 100 K or 4K7 and 10 K/22K. To create an “inbalance” when the supply voltage is switched to the circuit.

For beginners (& profs…) : (always…) use the advised transistors for first electronic experiments (in general, of course). Reason: they always work (!). So the BC 547 (NPN, Hfe 200-250) the BC 557 (PNP, Hfe = 200-250), the BD 139 (medium power NPN, Hfe=70-150) or the BD 140 (medium power PNP, Hfe = 70-150) or the 2N3055 (Hfe 50-70) or the 2N2219 for HF purposes up to 30 MHz.

When you want success in first experiments: buy/use them and always check their Hfe (= “GE” amplification factor) before soldering them into a circuit.

The circuit surely works with 2 x BD 139 or with one BC 547 B (TS1) and a Darlington of BD139-2N3055 (TS2-TS3).

Sorry to say: sometimes you buy BC 547 b on flea markets with an extreme amplification factor, say 400-500 or so. Throw transistors with unexpected high Hfe’s away, they were/are (in general) dumped on the hobby market by manufacturers, their “steilheid” is too high.

“Steilheid” (Dutch word) means the relation between input current on their bases (tiny) and the current between collector-emitter is too high, thus irrational, these transistors can only act as a “switch”.

Other types of transistors (apart from the mentioned) could (read: could…) give disappointing results in beginners and professional circuits & experiments, sorry to say.

All the videos hat I have published on You Tube can be found via my Channel Trailer: Link is

In thematic order you can find these video’s under the “comments” section.
Important: to find all the links to the (+/-700) video’s on my YT Channel, select, in the comments section, “NEWEST FIRST”

My books about electronics are available via the website from “Lulu”, search for author “Ko Tilman” there.

https://www.lulu.com/shop/search.ep?keyWords=ko+tilman&type=

There is an important video via which you can buy a document where I give links to many of my video’s, published between 2010 and 2018.

Link is: https://youtu.be/XXRsA24NUE0

My books are also available via Barnes and Noble and via Amazon.

Regarding all my video’s: I constantly keep them actual, so the original video’s with the most recent information are always on YouTube. That is the source, and search there. When my video’s are reproduced or re-edited on other websites/channels you can not (!) be sure about the original content (=really working electronics) and important adaptations to the circuits.

Be aware of that, I saw on the internet my circuits reproduced in a poor or even not proper way. I can not help that, sorry. Update 3 july 2019.