MSA-2743 RFIC Amplifier
Description
Agilent Technologies’ MSA-2743 is
a low current silicon gain block
RFIC amplifier housed in a 4-lead
SC-70 (SOT-343) surface mount
plastic package. Providing a
nominal 15.5 dB gain at up to
+18.5 dBm Pout, this device is
ideal for small-signal gain stages
or IF amplification. The
Darlington feedback structure
provides inherent broad band-
width performance. The 25 GHz f
t
fabrication process results in a
device with low current draw and
useful operation above 3 GHz.
A feature of the MSA-2743 is its
broad bandwidth that is useful in
many satellite-based TV, cable TV
and datacom systems.
In addition to use in buffer and
driver amplifier applications in the
TV market, the MSA-2743 will find
many applications in wireless
communication systems.
Application Guidelines
The MSA-2743 is very easy to use.
For most applications, all that is
required to operate the MSA-2743
is to apply 50 mA to 70 mA to the
RF Output pin.
RF Input and Output
The RF Input and Output ports of
the MSA-2743 are closely matched
to 50Ω.
DC Bias
The MSA-2743 is a current-biased
device that operates from a 50 mA
to 70 mA current source. Curves
of typical performance as a
function of bias current are shown
in section one of the data sheet.
Figure 1 shows a typical imple-
mentation of the MSA-2743. The
supply current for the MSA-2743
must be applied to the RF Output
pin. The power supply connection
to the RF Output pin is achieved
by means of a RF choke (induc-
tor). The value of the RF choke
must be large relative to 50Ω in
order to prevent loading of the RF
Output. The supply voltage end of
Rc is bypassed to ground with a
capacitor. Blocking capacitors are
normally placed in series with the
RF Input and the RF Output to
isolate the DC voltages on these
pins from circuits adjacent to the
amplifier. The values for the
blocking and bypass capacitors
are selected to provide a reac-
tance at the lowest frequency of
operation that is small relative to
50Ω.
V
d
C2
This layout provides ample
allowance for package placement
by automated assembly equipment
without adding parasitics that
could impair the high frequency
RF performance of the MSA-2743.
The layout is shown with a
footprint of a SOT-343 package
superimposed on the PCB pads for
reference.
Starting with the package pad
layout in Figure 3, an RF layout
similar to the one shown in
Figure 3 is a good starting point
for microstripline designs using
the MSA-2743 amplifier.
PCB Materials
FR-4 or G-10 type materials are
good choices for most low cost
wireless applications using single
or multi-layer printed circuit
boards. Typical single-layer board
thickness is 0.020 to 0.031 inches.
Circuit boards thicker than 0.031
inches are not recommended due
to excessive inductance in the
ground vias. This is discussed in
more detail in the section on RF
grounding.
Applications Example
The printed circuit layout in
Figure 3 is a multi-purpose layout
that will accommodate compo-
nents for using the MSA-2743 for
RF inputs from DC through 3 GHz.
This layout is a microstripline
design (solid groundplane on the
backside of the circuit board) with
50Ω interfaces for the RF input
and output. The circuit is fabri-
cated on 0.031-inch thick FR-4
dielectric material. Plated through
holes (vias) are used to bring the
ground to the top side of the
circuit where needed. Multiple
vias are used to reduce the
inductance of the paths to ground.
27x
C1
RFC
Vcc
Rc
C3
Figure 1. Schematic Diagram with Bias
Connections.
PCB Layout
A recommended PCB pad layout
for the miniature SOT-343 (SC-70)
package that is used by the
MSA-2743 is shown in Figure 2.
1.30
0.051
0.80
0.031
0.50
0.020
1.71
0.067
.080
0.031
1.15
0.045
Figure 2. PCB Pad Layout for MSA-2743.
Package dimensions in mm/inches.
9
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
