third-order intercept point (IP3)

A single figure of merit for how gracefully an amplifier or mixer handles strong signals before it starts inventing garbage. No real circuit is perfectly linear; push two close tones through it and its mild curvature creates new 'intermodulation' tones — the third-order ones land right next to your wanted signals, where no filter can remove them. IP3 is the (extrapolated) input or output power at which these third-order products would, in theory, rise to equal the wanted signal.

It's a clever extrapolation because you can never actually reach IP3 — the device saturates first — but the number predicts distortion at any backed-off level: every 1 dB you raise the input, third-order products climb 3 dB, closing the gap. Higher IP3 means a more linear, harder-to-overload front end. It pairs with the 1-dB compression point to fully describe a block's dynamic range, the span between the noise floor and the onset of distortion.