What happens to the output of an operational amplifier (op-amp) when the input signal exceeds the power supply voltage, leading to output saturation?

When the difference between the op‑amp’s inputs pushes the internal voltage beyond what the supply rails can support, the device can no longer linearly amplify the signal and its output voltage is forced to the nearest rail. This is called saturation, and the output settles at a voltage close to the positive or negative supply voltage, depending on the sign of the excess. The op‑amp then behaves like a saturated diode, no longer obeying the ideal linear relationship between input and output. For example, if an op‑amp powered at ±5 V is fed a 10 V differential input, its output will clamp near +5 V or –5 V instead of following the 10 V input. Thus the output no longer represents the input signal accurately and remains stuck at the rail voltage.