Shot Noise in Tunnel Diode Amplifiers

The contributions of Johnson noise and shot noise to the noise in a tunnel diode are analyzed according to a simple theoretical model. The current stream flowing across the junction in one direction is assumed to be uncorrelated with that flowing across the junction in the opposite direction, and both current streams are assumed to produce full shot noise. A simple parabolic band structure is also assumed. There is qualitative, but not quantitative, agreement between the predictions of this model and the experiment. On the basis of some simplifying assumptions (which are consistent with the experiment), the noise figure of a tunnel diode amplifier is calculated. A simple graphical method of determining the approximate noise figure of a diode from its current voltage characteristic is presented It is found that the noise figure has a broad minimum centered about a point slightly higher in bias than the bias value for maximum negative conductance.