Easy 2 transistor Sine wave oscillator (say for audio) with good properties: Demo and Schematic

Please read the description/textbox first. Easy to make and properly working 2 transistor sine wave oscillator, made with 2 x a BC 547 b (any NPN transistor with a Hfe (Bèta) of 300 x can do the job) and a phase shift network made with 3 capacitors and 3 resistors.

Everything is told in the video, also how to make it working on different audio frequencies. Max voltage is between 9 Volt and 12 Volt. That are the best supply voltages.

CORRECTION: with that 1 K resistor in series with the 10 K potmeter in the collector lead of the first BC 547 b transistor, you don't get to other frequencies, only the waveform gets more pure.

So no real frequency changes, the node of that 10 K potmeter was connected to another electrode in this circuit/video when making the demo. Sorry for that. Anyway: a purer waveform is also a good result, the resistance variation biases the transistor in a better way. Update: When you connect it (1K with a 10 K potm. in series) to the first electrode of the phase shift network it works very effectively in frequency changing.

On 2.23 I say "3 potentiometers" but of course I point to the fixed value resistors of (here) 47 K.

These fixed values of 47 K can (of course) be changed into 3 x a 47 K potentiometer. For experimental uses: in series with a 1 K to 2K2 fixed value resistor, to make that the oscillator will not stop when aligning/tuning the 3 of them to other frequencies.

You can also use a 2 stage potmeter of 47 K (3 stage potmeters are not easy to find!) and leave the first 47 K resistor fixed.

That will give a very big freq. change, surely over a bandwidth of 300 Hz-10 KC. With, of course, 3 x a 1N or 3 x a 3N3 or 3 x a 4N7 cap. in that phase shift network. Test, experiment, try.

With some experiments you can get from 100 Hertz to 20 KC, that is my idea. Takes some time, of course, experiment with the capacitor values and the resistor values in the phase shifting network. Now 10 N and 47 K. Change the values to get to other frequencies.

Thanks to Barry Blod. His YT Channel is here. https://www.youtube.com/channel/UCDKzKOpUOlJAYYNAUKHb8vg

Barry gave me the schematic at first hand. It did not want to work on first sight and I had to do some minor changes. But the whole schematic is/was in my opinion quite unique and thus (given its healthyness) a good idea to work it out more.

Especially when I found that the circuit oscillated in the 300 Hertz-800 Hertz range with only 3 capacitors of 10 N (0.01 uF) in the phase shift network, combined with the 3 x 47 K resistors.

That (low value caps on a low audio oscillator frequency) sounds very promising for further developments (!).

Say to get it to higher and lower frequencies in the (say) audio range (20 Hz-20 KC) with this electronic setup, is promising. Don't get disappointed by the way. Try e.g. 3 x a 1N (= 1000 pF) cap in that network. Or 3 x a 4N7 (= 4700 pF) cap.

The idea of using a Darlington for a sine wave oscillator is quite unique, because a Darlington has a very high current amplification (sometimes uncontrollable) and for a Sine Wave oscillator the amplification must be precise in the 1 X range, otherwise the sine wave will be distorted.

Say to a square wave or whatever kind of rare/strange waveform. Anyway: a very good circuit that needed some elaboration and has promises, thanks again Barry.

When you do minor experiments with cap. values and the resistor values pointed to in the video, you will not be disappointed. Good values to get to the audio & HF range range (20 KC max) : 100 N - 10 N- 1 N.

Or 470 N - 47 N- 4N7. Say max 15 KC.

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