These voltages form the two inputs of a single-Opamp subtractor circuit with unity
gain. Therefore, the final output taken across the output of the third Opamp with respect to
the ground node is given by v
o
v
o1
v
o2
(2k 1)(v
1
v
2
).
It may be verified that v
o1
v
1
and v
o2
v
2
when v
1
v
2
, quite independent of the
resistance values of the resistors in the three-resistor chain. This is so because, when v
1
v
2
, there is no current flow in them at all. Thus, the first stage comprising two Opamps con-
tributes the required differential gain without affecting the common mode gain. The second
stage contributes only unity gain to (v
o1
v
o2
). The common mode ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month, and much more.