Biomedical Engineering Reference
In-Depth Information
Fig. 13
Low-noise amplifier
(LNA) circuit schematic
together with the added
inductors
Vdd
L
L
R
L
L
D
M3
V
Cascode
M2
I
buffer
L
C
R
S
L
1
C
1
L
g
M1
C
P
V
in
L
2
C
2
L
S
Design Example for Ultra-Wideband Receiver
The general block diagram of a UWB receiver was introduced previously in Fig.
7
.
In this section, an example design and implementation of a UWB LNA and a mixer
as two of the most important blocks of the receiver will be presented.
Ultra-Wideband Low-Noise Amplifier
Gain and Bandwidth
In the design presented, a CS (Common Source) configuration with inductive de-
generation and a multi-section reactive network for input matching is utilized. The
matching network is first proposed in [
24
]. Also, two auxiliary inductors are added
to boost the bandwidth of the amplifier. In the circuit shown in Fig.
13
, the drain
current
i
d
can be written as
i
d
=
V
G
g
m
s
(
C
p
+
F
(
s
)
V
in
g
m
s
(
C
p
+
C
gs
)
ω
t
L
s
=
C
gs
)
ω
t
L
s
,
(1)
assuming
F
(
s
) is the Chebyshev filter transfer function. In the above analysis,
C
gd
is not taken into account. This is mainly because of the very low impedance of the
cascode stage seen from drain of M
1
. This will result in very weak Miller effect on
gate of M
1
,so
C
M
is
C
M
=
C
gd
(
1
+
g
m
(
r
o
R
L
)
)
.
(2)
Here,
R
L
=
1/
g
m2
is small enough to make the Miller capacitance negligible, so the
LNA gain without considering
L
D
and
L
C
will be
v
out
v
in
=
−
F
(
s
)
g
m
s
(
C
p
+
(
sL
L
+
R
L
)
C
gs
)
ω
t
L
s
∗
C
gd3
)
.
(3)
1
+
sR
L
(
C
db2
+
C
gd3
)
+
s
2
L
L
(
C
db2
+
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