What happens to the op-amp output when it enters saturation?

When an operational amplifier (op-amp) enters saturation, it means that the output voltage reaches its maximum or minimum limit and can no longer increase or decrease in response to the input signal. In the case of positive saturation, the output rises to the maximum voltage the op-amp can deliver, which is typically close to the positive supply voltage. This condition occurs when the input voltage differential exceeds the op-amp's ability to regulate the output within the linear region.

In this saturated state, the op-amp is not functioning as a linear amplifier anymore; instead, it is acting as a comparator. This behavior is tied directly to the characteristics of the op-amp, where the output is driven to its maximum to reflect the input conditions, leading to the situation where it can only either go high (saturation near the positive supply) or low (near the negative supply or ground). Thus, when an op-amp reaches saturation, it signifies that it is outputting the maximum voltage, reinforcing the idea that the output rises to maximum voltage under these conditions.