Environmental Engineering Reference
In-Depth Information
where in the last expression we defined
and used equations
(8.9a)-( 8.9b).
To evaluate we now leave the input open. Under this condition, the
amplifier input voltage for the circuit in Fig. 8.10 (8.11) is solely determined
by and is independent of the output voltage. Hence, the PSD of the
output noise voltage for the two circuits is respectively
and by equating the two above equations we get
Equations (8.18) and (8.20) show that the equivalent input noise current of
an amplifier is unmodified by the application of series-mixing feedback,
while the noise voltage of the feedback network adds directly to the closed-
loop input-referred noise voltage.
