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).