Question
Does the OP97 have overvoltage protection and for how long is it protected?
Answer
The o/p of the OP97 includes circuitry that limits the current o/p to generally
about 10mAmps, when the o/p is shorted to gnd or to either supply. Therefore
you do not need to worry about the length of time that the o/p is shorted to
GND via your o/p diode.
O/p short circuit protection - indefinite - implies that the o/p can be short
circuited for a long/ unknown period of time without damage, as the o/p stage
will limit the current.