I calculated the size of the current source for the DAC, but the size came out to
long channel and narrow wide, about 3/20
I think the transistor could be operated in the weak inversion region with that size.
Is there any problem on that?
which kind of your DAC you are designing and how do you come up this number?
Theoritically, it's possible you have such device and make them operating at the sub-theshold region. I have done of this DAC and it works fine.