This application note describes a method for accurately measuring the third order intercept point for low distortion IC products such as the LT5514. This includes the test setup, test equipment, test signal and interpretation of the measurement results.
The document describes precautions and procedures required to evaluate the linearity performance of low distortion ICs like the LT5514. It details a two-step evaluation method: first optimizing the test setup with signal generators, combiners, and attenuators, and secondly evaluating the LT5514 demo board performance by adjusting gain and net attenuation.
The two-tone test signal should be set to a power level of –23dBm.
Matching resistor R7 (255 Ω) must be removed from the LT5514 demo board.
The differential output impedance is 200Ω when R7 is open.