This question was asked to me in a VIVA. What examiner asked. How do Sinusoidal output comes out in the Wein-Bridge Oscillator. ............ I tried to solve the problem using the control system. That is, by deriving the transfer function of the Wein-Bridge Oscillator, but first i got confused on where to take the input as there is no input and oscillators work due to noise input(this is what written in the books). Then i assumed the input to be the negative Op-Amp terminal, this time the confusion was on what function the input Voltage should be? I have studied two Sinusoidal Oscillators, another one is phase-shift oscillators, and I don't know the 'How' of Phase-Shift oscillators also. The book i follow is Sedra-Smith and doesn't say anything about the 'How' behind the generation of Sinosoidal output. I have one more book on Op-Amp Circuits and nothing is written about it this in that book also.