The data sheet for the AD623 lists the supply-voltage range as +-2.5V to +-6V in dual-supply mode, but as +2.7V to +12V in single-supply mode (Table 4).
The maximum voltage makes sense; +-6V is the same 12-volt difference as 0 to +12V. But the minimum supply voltage doesn't make sense -- I would expece the minimum 2.7V single-supply voltage to correspond to +-1.35V, not to +-2.5V.
What am I missing here? The device itself doesn't even have a ground pin, so I'm not sure how it would even "know' which mode it's in. Apologies if I'm missing some basic knowledge of how specs work -- I'm usually a digital person but trying some analog stuff at the moment.