What is the primary characteristic of an operational amplifier (op-amp) in an open-loop configuration, specifically regarding its gain?

An op‑amp in open‑loop mode has an enormous voltage gain, typically on the order of 100 000 or more. This means that a tiny voltage difference between the two inputs is multiplied by that huge factor, so even a microvolt difference can push the output toward the supply rails. Because the gain is so high, the op‑amp will saturate quickly unless the input difference is kept extremely small or feedback is added. For example, if the inputs differ by just 1 mV, the output will try to reach 100 V, which is far beyond the supply voltage, so the op‑amp will clip at the supply limits. This gigantic open‑loop gain is why feedback is almost always required to make the device useful.