A square-law clamping circuit (99, 120) sinks a current from an input/output terminal proportional to a square of a difference between a voltage thereon and a reference voltage. A first MOS transistor (130) has a source for receiving the reference voltage, a gate, and a drain coupled to its gate. A current source (134) coupled to the drain of the first MOS transistor (130) sources a predetermined current therefrom. A second MOS transistor (132) has a source providing the input/output terminal (100, 121), a gate coupled to the drain of the first MOS transistor (130), and a drain. A current sink (135) coupled to the drain of the second MOS transistor (132) sinks a current therefrom.
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