LM358 opamp unity gain cap

Question

I'm using an LM358 op-amp for unity gain (feedback to V-). However, I'm getting some unexpected results. When Vin is from 0v - 3.75v, op-amp output is as expected 0 - 3.75v. However, when Vin is greater than 3.75v, op-amp output is capped at 3.75v, even though Vcc is 5v. Can someone help shed some light to why op-amp unity gain can be less than 1?

LM358 datasheet can be found here: http://www.onsemi.com/pub/Collateral/LM358-D.PDF

Answer 1

It's right there on page 4:

Output Voltage−High Limit (V_OH): V_CC = 5.0 V, [...] | 3.3 | 3.5 | - | V

Answer 2

The LM358 isn't rail-to-rail. The output cannot be driven to Vcc.