I need to analyze a Wien-Bridge Oscillator for stability. Over the last day or so, I've taught myself to understand different op-amp circuits where I have well-defined V(in) and V(out). For the oscillator circuit though, there really is no such thing as V(in). There's a V(out) which evolves with time, and if the circuit is stable, reaches some steady state value. Is there some standard way to analyze such a circuit? Do I have to set up differential equations, or can I just look for poles in the loop gain (or loop transmission...I'm not too familiar with the terminology)? A reference will be useful; ideas will be appreciated. For the Wien-Bridge oscillator, see Horowitz & Hill, Section 4.14 (p 165,166).