Gate noise in field effect transistors at moderately high frequencies

At higher frequencies the gate noise of a field effect transistor increases rapidly with increasing frequency. This effect is here attributed to the thermal noise of the conducting channel and is caused by the capacitive coupling between the channel and the gate. The noise is represented by gate and drain noise current generators i
g
and i
d
, respectively; an approximation method is developed that allows calculation of i
g
²
, i
d
²
and i
g
× i
d
for moderately high frequencies. The correlation coefficient of i
g
and i
d
is imaginary and amounts to about 0.40j under saturated conditions, i
g
²
can be expressed in terms of the noise resistance R
n
, and the gate-source capacitance C
gs.
It is shown that the correlation has only a slight influence on the noise figure F and that (F
min
- 1) varies as ωC
gs
R
n
over a wide frequency range.