How does this oscillate

145

03:47:07

I really don't get why it oscillates. Maybe the base voltage sags and the hysteresis takes place or something. Anyway whats your opinion 

published 9 years ago

hurz

9 years ago

Feedback is coming from input current this circuit takes. Check this which is perfectly seperated http://everycircuit.com/circuit/5555636741341184

thebugger

9 years ago

Yes I figured that much. The 1Mohm resistor is too large and the voltage sags, and probably the hysteresis makes it oscillate. It's interesting though, I was going for stable operation, but I got an oscillator

hurz

9 years ago

Yes, its a little fragile but with some finetuning it will work in reality. Hfe of first bjt and 1Mohm are most critical and allow only inside a small window to operate.

thebugger

9 years ago

Yes it's a wonder I found the right window.

2ctiby

9 years ago

Just an idea..any use? : http://everycircuit.com/circuit/5709958875709440

thebugger

9 years ago

The use of a resistor decreases the pulse width. Maybe it's somewhat useful, for some sort of a sawtooth generator. They're usually driven by sudden spikes

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