The most suitable type of Camera for taking photographs suitable for a portrait is a good quality digital camera able to take a high resolution picture. However many photos are now taken with a mobile phone or tablet as many of us have one of these close to hand. Modern Smart phones and tablets that can take good quality high resolution photos and are perfectly acceptable.
It is very important to capture as much detail at high resolution as possible so that features such as the eyes, eyelashes and hair are clear. The two photos below indicate the difference in a photograph taken with low resolution and high resolution camera.