A wideband LNA with dual-feedback for TV tuner

Abstract

A wideband LNA is the first amplifying stage in TV tuner system. It requires a low noise figure with a sufficient gain and a high linearity such as high IIP2 and IIP3 due to the many adjacent channels. This paper represents the wideband CMOS LNA using a dual feedback for the tuner application, which can suppress the second and the third order distortions with a low noise and a suitable gain. In the dual feedback, the weak negative feedback improves the linearity of the transconductance partially, thereby maintaining the high gain and low noise. The residual distortion and the distortion of the buffer are cancelled by the positive feedback. Consequently, the proposed wideband LNA with the dual feedback improves noise figure and linearity with a high gain. The LNA fabricated in 0.18 µm RF CMOS demonstrates the expected performances.