 This figure could be 6 dB for testing an amplifier with 40 dB gain and could be 16 dB for an amplifier with less gain or higher noise.To determine the noise figure of an amplifier we use a noise diode at the input to the amplifier and determine the output noise "Y" with the diode switched on and off.With knowledge of Y and a knowledge of ENR we can then determine the amount of noise contributed by the amplifier and hence we can calculate the noise figure of the amplifier.