Zum rail to rail input:
http://www.maxim-ic.com.cn/appnotes....te_number/741/

Beyond-the-Rails Inputs

Maxim's Beyond-the-Rails input structure includes overvoltage protection.

Devices with Beyond-the-Rails inputs are designed especially for low-power single-supply operation. The input stage consists of separate npn and pnp differential-transistor pairs (Figure 1). Together, they provide a common-mode input voltage range that extends beyond both supply rails. The npn pair typically connects to the top rail (VCC), and the pnp connects to the bottom rail (VEE).