Nonlinear analysis of noise in current-steering variable gain amplifiers

This paper investigates the difference between the small-signal noise figure and the noise figure in the presence of a large signal at the input of a current-steering variable gain pair. The mechanism of noise generation in the presence of a large signal at the emitters of the current-steering pair is analyzed for single-ended and differential operation. An analytical equation for the large-signal noise figure is derived. The results are applied to a cable TV IF amplifier and compared to measured data.