In BJT for working in active region for a common emitter configuration emitter and base should be in forward bias and base and collector should be in reverse bias. But in case of voltage we say that base-collector voltage should be less than 0.4V.
But if V(base)-V(collector)=0.1 (suppose) then base-collector junction will be in forward bias that means it will enter into saturation mode. But book says it will remain in active mode. How is it possible?