What is the output resistance of the AD623ARM Instrumentation Amplifier?
The output is active and will be maintained as a low impedance by the action of internal feedback.
If you need to work out the drive capability of the output, the AD623 can drive a 10k load from a +5V single supply to datasheet limits of 10mV above Ground and 500mV below +Vs.
The output is short circuit protected, which allows the output to be permanently connected to either power rail without damage.
Also refer to Figure 39 - output swing vs current load.