Hi

How does this simple NPN transistor work as an oscillator? I have it oscillating on breadboard but slightly confused about how it works....

Can someone PLEASE explain it to me step by step!

Pic attached....

Thanks

 

Oh, my. I haven't seen this one in a while -- a Colpitts oscillator. The resonant frequency is determined by the parallel resonant L-C combination -- the C part comes from C1 and C2 in series.

 

Check up Colpitts oscillator.

http://en.wikipedia.org/wiki/Colpitts_oscillator

An oscillator is not restricted to NPN transistors. A PNP transistor will work too with the proper modifications to the supply polarity.

Basically, the LC network creates a phase shift of the signal from the output and feeds it back into the input. This causes the circuit to oscillate.

 

I'm dating myself, but when I learned about Colpitts oscillators, it was with vacuum tubes.