Hello
Here is a site about wien oscillator http://sound.westhost.com/project22.htm
and i have this circuit:
The question is: how it is possible that this circuit starts to oscillate when there is no input , I've understand that the meaning of oscillation is that there is some input, lets say a little ac (or radiofrequency), and now when this voltage comes in then the opamp will amplify it and the the positive feedback feeds back the output ac and the opamp again amplifies, and this loop goes around until the maximum gain is obtained. Is this right? And the output oscillation frequency depends on the choosed resistors and capacitors [f=1/(2*pi*RC)], so the input frequency and output frequency are not the same?
Or is it so that the input can be just a dc voltage which makes the capacitors charged and the opamp will discharge them and feeds back the signal, and this charging and discharging will give us a sine wave in output?
I've read many texts about oscillators and their circuits, put there isn't any information about the input, which will make the oscillator circuit to start the oscillation.
And also this circuit, there is +12V supply voltage, but there is no input which would make the BJT to open and go to amplifying regime. If the transistor is not opened then there is no use of the positive feedback in my knowledge.
napos
Here is a site about wien oscillator http://sound.westhost.com/project22.htm
and i have this circuit:
The question is: how it is possible that this circuit starts to oscillate when there is no input , I've understand that the meaning of oscillation is that there is some input, lets say a little ac (or radiofrequency), and now when this voltage comes in then the opamp will amplify it and the the positive feedback feeds back the output ac and the opamp again amplifies, and this loop goes around until the maximum gain is obtained. Is this right? And the output oscillation frequency depends on the choosed resistors and capacitors [f=1/(2*pi*RC)], so the input frequency and output frequency are not the same?
Or is it so that the input can be just a dc voltage which makes the capacitors charged and the opamp will discharge them and feeds back the signal, and this charging and discharging will give us a sine wave in output?
I've read many texts about oscillators and their circuits, put there isn't any information about the input, which will make the oscillator circuit to start the oscillation.
And also this circuit, there is +12V supply voltage, but there is no input which would make the BJT to open and go to amplifying regime. If the transistor is not opened then there is no use of the positive feedback in my knowledge.
napos