Moving on to talk about how the transfer function of RF detectors varies from device to device. The thick black trace in this plot represents the transfer function at 2GHz of approximately thirty ADL5902 RMS detectors drawn from different production lots. For a particular fixed input power level, say -35dBm for example, Vout can vary by 250mV from device to device. The ADL5902 has a slope of approx 50 millivolts-per-dB, which corresponds to a variation of approximately 5dB. So while RF detectors provide excellent transfer function linearity and temperature stability, they generally do not provide good absolute accuracy. So, some level of calibration is required to achieve any useful level of accuracy.