Radio Frequency Integrated Circuit Design - Webs

LNA Design
i 2 on_tot = i 2 n Z 2 � g 2 m
Similarly, for the model in Figure 6.15(a),
i 2 on_tot = i 2 bn Z 2 � g 2 m + i 2 cn
Now solving (6.44) and (6.45) for in gives
where i 2 bn = 2qIB and i 2 cn = 2qIC .
i 2 n = 2qI B + 2qI C
g 2 m
Y 2
�
6.3.2 Noise Figure of the Common-Emitter Amplifier
161
(6.44)
(6.45)
(6.46)
Now that the equivalent input-referred noise model has been derived, it can
be applied to the results in Chapter 2 so that the optimum impedance for noise
can be found in terms of transistor parameters.
The input-referred noise current has two terms. One is due to base shot
noise and one is due to collector shot noise. Since collector shot noise is present
for both vn and i n , this part of the input noise current is correlated with the
input noise voltage, but the other part is not. Thus,
Likewise, in the case of the vn ,
i 2 c = 2qI C
g 2 m
Y 2
�
(6.47)
i 2 u = 2qIB (6.48)
v 2 c = 2qIC
g 2 m
(6.49)
v 2 u = 4kTr b (6.50)
The correlation admittance Yc can be determined (see Section 2.2.5). It
will be assumed that at the frequencies of interest the transistor looks primarily
capacitive.