I think the output of a system that has unwanted positive feedback would be nonlinear and be composed mostly of spurious oscillations triggered by the inherent noise frequencies present at the input of the system.
Most oscillators use intentional controlled positive feedback to sustain oscillations and use inherent noise at their input to start the oscillations. The output frequency of the oscillator is determined by tuned circuits that determine which frequency is allowed to be fed back to the input to sustain oscillations at that particular frequency.
With this being considered and not knowing whether the positive feedback is intentional or not in the system you are talking about then I am not sure it is possible to say what the output would be. Could be damn near anything except what you want I suppose.
Depending on the dynamics the system will either saturate or oscillate. Usually a system with positive feedback will oscillate, but if it has an infinite bandwidth (which is not really possible) it will saturate.
Positive feedback increases the total gain until it becomes oscillating.
for +ve feed back system will not be stable either it will hit upper/lower limit of saturation of the system.
Tthe output will go to a maximum (saturate).
systems and signals
