questions about mos ratio

[smilelangjun]

In theory, with a preconditon of big area, the op's input pair should have a big ratio,and the current mirror mos should have a small ratio, in order to minimize the offset voltage.
But i have seen the photoes of ADI'schip, the condition is just opposit, can anybody tell me why? Did they make a mistake?
thanks a lot.

 

[hn1]

the I/O devices can have low ratios but the gate oxide of I/O devices are bigger than the other transistors on the chip.

 

[smilelangjun]

thank you, but I was talking about the inner circuit in the chip, not IO devices.