I would first like to explain you how the depth of field works. The depth of field depends on several factors and aperture settings are one of them. The other factors are the lens’s focal length, distance of subject from background and distance of subject from the camera. You can basically not control the aperture or the lens’s focal length, you can eventually get a shallower depth of field by minimizing the difference between the camera and the subject. When you move the camera closer to the subject, the background will fall out of focus. So you will get sharp focus on the subject and the background will be blurred, just like the background blurs for human eye, when we focus on the subject closer to us.