Noise Cancelation? Explained!: The Role of Feedback in Noise-Canceling LNAs and Receivers

Inductorless wide-band low-noise amplifiers (LNAs) usually suffer from poor noise performance, mainly due to the high noise contribution of the matching device. Noise canceling (NC) is a technique used in wide-band LNAs [1]-[13] to nullify the noise contribution of the matching device at the output. NC techniques are often explained with the help of the block diagram shown in Figure 1(a), where the input signal from a source of internal impedance Rs is simultaneously fed to a matching amplifier and a voltage sensing amplifier.