LMH6654 Datasheet, PDF (15/17 Pages) National Semiconductor (TI) – Single/Dual Low Power, 250 MHz, Low Noise Amplifiers

Application Information (Continued)
The NF is increased because the R_T reduces the input signal
amplitude thus reducing the input SNR.
(4)
The noise figure is related to the equivalent source resistance (R_seq) and the parallel combination of R_f and R_g. To minimize noise
figure, the following steps are recommended:
1. Minimize R_f||R_g
2. Choose the Optimum R_s (R_OPT)
R_OPT is the point at which the NF curve reaches a minimum and is approximated by:
R_OPT ≈ (e_n/i_n)
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