harpoon
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hi watt
a very general rule of thumb is to size all transistors to have a gm/i of ~10.
then for more speed, you size it greater than 10, and use minimum L
for mirrors, use large-ish L, in the order of 1u (on a 0.13um/0.18um process) to get good matching.
for low flicker noise, use large WxL area.
One thing to start thinking is about layout. It looks neater when transistors have uniform dimensions (e.g. use L=1u, 2u, etc ... rather than 1.12u, 2.38u etc ...)
the most crucial part of the design (and most often forgotten) is not the sizing of the devices, but rather the BIASING.
One good book to follow is ... CMOS: Circuit Design, Layout, and Simulation R. Jacob Baker
i think he also has some lectures which you can follow online ...
good luck !
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