In the small signal circuit shown, the enhancement mode $n$-channel $\text{MOSFET}$ is biased in saturation with transconductance $g_{m}.$ If channel length modulation is ignored, the small signal impedance looking into the node $\text{P}$ is given by ______________
- $R_{S} || R_{L} || g^{-1}_{m}$
- $R_{S} || g^{-1}_{m}$
- $\left(R_{S} + R_{L}\right) || g^{-1}_{m}$
- $\frac{R_{L}g_{m}}{1+R_{S}g_{m}}\left( R_{L} || g^{-1}_{m}\right)$