Why
do you call the reference in Fig.
20.14 a Beta-Multiplier Reference (BMR)
instead
of calling it, as you show on
the top of page 625, a constant-gm
reference?
The
BMR is only a constant-gm
reference when the MOSFETs
follow the (long
channel)
square-law equations. Since
CMOS circuits in production for the
last
20+ years can't (accurately) be
described using the square-law equations it’s
best
to describe the reference by how
the MOSFETs are related, one’s Beta is
multiplied
up from the others.
Also
note that the name BMR is similar
to the name BGR (bandgap reference).