*4.1. LNTA Design*

Two well-known LNTA topologies, common-gate (CG) and common-source (CS), can be used. The CS LNTA is suitable for very-low-noise applications at the cost of a narrow RF bandwidth. It is also very susceptible to non-idealities related to fabrication and packaging. On the other hand, the CG topology is used for wideband matching, and it is more reliable. The input impedance looking into the CG LNTA is 1/gm. Very high current and large device sizes are required to achieve the 1/gm = 50 Ω. To overcome this, a capacitor cross-coupled (CCC) technique is used to boost the effective *gm* by two times without consuming extra power. It also improves the NF. The LNTA circuit is formed by MCG, Rb, and CAC. The noise factor of the LNTA is given by

$$F = 1 + \frac{\gamma}{R\_S \times g\_m},\tag{8}$$

where RS is the source impedance and *γ* is the short-channel effect coefficient, and can be reduced by increasing the transistor lengths.
