The output of a operational amplifier will reach saturation when Vin X Gail >= upper power supply voltage.
or -Vin X Gail >= lower power supply voltage. What happens is the internal transistors in side the opamp become saturated or can no longer increase
If you look at the the data sheet for an opamp it is called output voltage swing and the the power supply voltages are usually mentioned and output current for that voltage
bob j
