1) In
Ch. 20, on page 629 in Fig.
20.22, I am unclear of the reason *V _{reg}*
is

connected
to the gate of M2. Without
that connection it would still work.

2)
There is also a second feedback due
to the cross-coupled MOSFET. What

is
the function? How would that affect
the DC operating point and stability?

*V _{reg}*
is connected to the gate of M2 to make

20.19
*V _{reg}* is a
high impedance node (meaning only drain
connections). By diode

connecting
M2 (connecting the gate and
drain of M2 together so that its small

signal
resistance is 1/*g _{m}*)
we only have one
high-impedance node (in Fig. 20.22),

that
is, *V _{biasp}*.
The reason for
doing this is to make the feedback in the circuit

easier
to make stable. The circuit in
Fig. 20.19 is a two stage op-amp, a diff-amp

and a
common-source amplifier made with
M4. These topics are discussed in detail

in
Ch. 24.

The
reason I put that circuit in Ch.
20 instead of waiting until after we discuss

those
topics in Ch. 24 is so that we
have a practical biasing circuits for

designing
amplifiers and current
mirrors in Chs. 21-23.
Practical biasing allows

us to
use real circuits for analysis
and design.

The
second cross-coupled MOSFET is used
so that we have something to compare to

*V _{reg}*.
We want the drains of M1 and M2 to be the same potential to minimize
the

effects
of *VDD* variations.