mga-31189 Avago Technologies, mga-31189 Datasheet - Page 4

• Manufacturer Part Number: mga-31189
• Description: 70 To 500 Mhz Ampliier For If Applications Using The Avago Technologies Mga-31189 Ampliier
• Manufacturer: Avago Technologies

Application Example
In order to demonstrate the suitability of the MGA-31189
as an IF band amplifier, the device is tuned and optimized
to four IF bands, 70 MHz, 170 MHz, 240 MHz and 500
MHz. Table 1 shows the IF frequency bands with their end
application.
Table 1. Typical IF band and their applications
For most applications, all that is required to operate the
MGA-31189 is to apply a DC bias of +5 V and match the
RF input and output. The following discussion describes a
typical application for the MGA-31189 for four different IF
bands. Design steps discussed include matching the input
and output as well as providing a DC bias while maintain-
ing acceptable linearity, gain and noise figure perfor-
mance. The four IF amplifier designs were based on the
typical requirements shown in Table 2.
Table 2. Typical IF amplifier requirements
Impedance Matching
The most important criteria when designing with the
MGA-31189 is choosing the input and output-matching
network. The MGA-31189 MMIC is designed to give an
excellent 40 dBm of OIP3 across the band, but in order to
achieve this performance the input and output matching
networks must present specific impedances (*
to the MGA-31189. Matching to the input and the output
of the MGA-31189 can be modified to make tradeoffs
between IP3, NF and return loss performance.
4
Frequency (MHz)
70
153.6
170
204
240
465
500
1
2
3
4
5
Parameter
Input Return Loss (IRL)
Small Signal Gain (SSGain)
Reverse Isolation (ISO)
Output Return Loss (ORL)
Output Third-Order Intercept
Point (OIP3)
Application
CDMA BTS
3G BTS
GSM
TD/SCDMA
Wireless Data
GPS
Broadband Access
Performance
≥ 10
≥ 20
≥ 27
≥ 10
≥ 40
Unit
dB
dB
dB
dB
dBm
S
and *
L
)
Table 3. Required matching for NF, IP3, IRL, ORL and Gain
In general, matching for minimum noise figure does not
necessarily guarantee good IP3 performance nor does
it guarantee good gain. This is because the impedance
parameters for the MGA-31189 are not guaranteed to lie
near each other on a Smith chart. If all input matching pa-
rameters are near each other, or at the same point, and all
output parameters also lie near each other, or at the same
point, the amplifier would have minimum noise figure,
maximum IP3 and maximum gain, all with a single match.
Practically, this is not the case, and some parameter must
be sacrificed to improve another. Table 3 lists the input
and output parameters required for each type of match,
and Figure 6 depicts how each is defined.
Figure 6. Typical impedance matching requirement for microwave FET and
MMIC amplifiers
OIP3 depends on the input and output match, but in
practice, OIP3 largely depends on the output match. Of
course, these points are valid at one particular frequency
point, and other frequencies will follow the same design
rules but will have different locations. Also, the location of
these points is largely due to the manufacturing process
and partly due to IC layout, but in either case, further dis-
cussion is beyond the scope of this application note
Matching Purpose
IP3
NF
IRL
ORL
SSGain
50 :
Gain
Match
Input
IP3
NF
*
*
S11*
opt
S
*
*
S11
Input Tuning
*
*
S11*
none
S11*
opt
S
S
opt
*
*
11X
*
S22
L
*
*
S22*
L
Output Tuning
*
none
none
S22*
S22*
Output
Match
L
50 :