Environmental Engineering Reference
In-Depth Information
after simple calculations we get
where and are the PSD of and , respectively.
The above equation shows that both input referred generators are required
to model the noise of the amplifier for any value of
In fact, if we used
only
no output noise due to the amplifier would be generated so
long as
is zero (infinite). Therefore, the value of
determines which of
the two noise generators is dominant.
The PSD of the output noise divided by the square of the magnitude of
the system gain gives the expression of the equivalent input noise voltage
PSD,
Thus, if the value of the source
resistance
is
specified, the three
noise
sources may be modeled by only one noise generator of PSD
as shown
in Fig. 8.3
