Conditions for optimum noise performance in l.f. amplifiers employing junction f.e.t.s

Increasing the drain current of an f.e.t. can result in an improvement of the noise performance at medium frequencies, but, owing to changes in the noise spectrum of the device, a deterioration of the low-frequency noise performance can result. Measurements in the frequency range 1 Hz¿1 kHz on some low-noise samples of f.e.t.s show that the drain current is not critical up to a limit, but, above this limit, the noise performance below 10 Hz deteriorates rapidly.