Why aren't low noise amplifiers used for receivers implemented in oscillators?

[generic_name]

When I open textbooks I normally see BJTs, or FETs, in the feedback loop but never an ultra low noise op amp, or other type of very low noise amplifier.


I was hoping someone who has designed oscillator circuits can tell me why aren't low noise amplifiers (LNAs) normally used for receiver applications not used in oscillator circuits?

 

[Anatol]

AFAIK BJT and FET in feedback loop of oscillators used for stabilization of oscillator output amplitude, i.e. as nonlinear devices. Amplifiers aro not very well siuted for this function.