Without doing a full circuit analysis, and assuming the 13,8V battery is the load on this circuit, I would say it sets the time constant of a slow pulsing oscllator. It looks like some kind of battery charger circuit that changes pulse width as the cells reach full charge.
Thanks betwixt and bhav
i want to know when we rise capacitor voltage with op-amp and capacitor try to charge we have a short circuit between op-amp and transistor and when capacitor charge fast the transistor getting off.correct?