Well suited topology for broadband LNA design. Schematic of the LNA with resistive termination is shown in Figure 1(a). The resistive termination() at the input provides broadband impedance matching over a wide frequency band.
The equivalent circuit of resistive termination LNA is shown in Figure 1c.
Gain of LNA,
Noise Factor of LNA is given by
noise power at the input of LNA due to the source
noise power added by the LNA referred to the output
where, . When , then noise factor is
Therefore the noise figure of Resistive terminated LNA is > 3dB.