d7i dof

Hi all
The lower the apperture the more dof and vice versa...
i guess this is right no ??
i wonder why it is so hard to get good dof...
i mean subject sharp ... background unsharp
it was easy with my old camera "canon a1"
but not with my 7i
is this typical for digi cam's ???
or am i doing something wrong here ...???
please help my friends
regards
Rik