Tags: architectures, classic, current mirror
The simplest current mirror. M2 mirrors current Iref flowing through transistor M1, due to the same gate-source voltages (VGS1 = VGS2). Iout current may be different than Iref current due to the fact that M2 drain voltage may be different than M1 drain voltage.
Output resistance Rout is equal to output resistance Rds2 of M2 transistor.
Iref starts to be properly mirrored from VOUT = VDS2sat.