AMPLIFIER

摘要

A low-noise amplifier (LNA) may be configured as an inductively-degenerated LNA or as a common-gate LNA. Inductively-degenerated operation is selected by disabling the series switches SW1, enabling the common-source transistors M2p,m, and disabling the common-gate transistors M1p,M1m. Conversely, the LNA is configured in common-gate mode by enabling SW1, M1p, M1m, and disabling M2p,M2m. The inductively-degenerated LNA has a lower noise figure but requires external inductors Lextp, Lextm. The common-gate LNA has a higher noise figure, but has better linearity and bandwidth and it requires no external matching components. A shunt capacitor may be placed in parallel with the inductors (figure 9) to allow use of smaller inductors. Cross-coupling of input signals (figure 6) allows lower operating current. Feedback may be used (figure 5) to reduce the noise figure.