When you cascade gain stages in an amplifier, each stage contributes a pole. With three or more poles inside a feedback loop, the phase shift can exceed 180° before the loop gain falls below unity — and your "amplifier" becomes an oscillator. Dominant-pole compensation is the most common fix: deliberately add a low-frequency pole so the gain rolls off at –20 dB/decade and crosses unity gain before the other poles add significant phase shift.

The idea is brutally simple. If your uncompensated amp has poles at 1 MHz, 10 MHz, and 50 MHz with an open-loop DC gain of 100 dB, you have ~270° of phase shift accumulating by 50 MHz — wildly unstable under feedback. Add a dominant pole at, say, 10 Hz, and the gain now rolls off cleanly from 100 dB at 10 Hz, hitting 0 dB at 1 MHz (the old first pole). At that crossover, only the dominant pole has contributed phase shift (–90°), giving you a healthy 90° phase margin.

How to implement it:

• Shunt capacitor at a high-impedance node — common in discrete designs. The pole sits at f = 1 / (2π·R_node·C).
• Miller compensation — a small cap from output to input of a gain stage, which multiplies the effective capacitance by the stage gain. This is what's inside nearly every monolithic op-amp.
• External comp pin on uncompensated op-amps like the LM301 or LT1097 — you pick C_c based on your closed-loop gain.

Concrete example: The classic LM301A has an external compensation pin. For unity-gain stability, datasheet says 30 pF. But if you only need a closed-loop gain of 10, you can drop to 3 pF — because feedback only attenuates the loop gain by 20 dB, you can let the dominant pole sit 10× higher in frequency. Result: 10× the bandwidth for the same phase margin. This is why "decompensated" op-amps exist — they trade unity-gain stability for bandwidth at higher gains.

Rule of thumb: Place the dominant pole such that the gain-bandwidth product equals the frequency of your second pole. So if the next pole is at 5 MHz and DC gain is 10⁵ (100 dB), put the dominant pole at 5 MHz / 10⁵ = 50 Hz. This guarantees the second pole hits exactly at the unity-gain crossover, giving ~45° phase margin — marginal but stable. For 60° margin (the usual target), push the dominant pole down another factor of 2.

The cost? Bandwidth. You're throwing away gigahertz of potential to buy stability. That's the deal — and it's almost always worth it.