On
page 1146 in the third paragraph you
indicate that you can't use
the
topology seen in Fig. 31.19 for the
TIA because it's not inverting.
However,
if the input current goes up
the output voltage goes down so
isn't
it inverting?
Yes,
you are right and this is a good
question. The reason you can't use
this
topology is that the reset device,
M5 in Fig. 31.51, must be connected
between
a high-impedance node and a
low-impedance node for the reset to
work
properly. This means that the reset
device can't be connected back to
the
input in Fig. 31.19.
The
key thing is that M5 can't have a
DC current flowing in it if the reset
is to
work correctly. If M5 does pass a
current then the biasing will be
corrupted
when M5 shuts off causing the
amplifier's output to move towards
either
vdd or
gnd.