Am i expecting too much from my Nex-7 with Minolta 50mm 1.7?

(A bit simplistically) degree of background blur depends on the following:

Lens focal length (longer better), sensor size (larger better) , aperture (wider better), subject distance (shorter better), background distance (longer better).

At the nearest focus of most 50mm lenses you get shallow DOF and good background blur, even stopped down significantly.

DOFmaster.com has a few handy DOF calculators. Apps for devices are also available,