Application Notes

H
High IP3 MMIC LNA at 900 MHz
Application note for the BGA2011
The BGA2011 is a MMIC LNA for cellular applications at 900 MHz that require good linearity,
like CDMA. The MMIC is produced by the single metal DPO Philips process and is packaged
in a 6-pin SOT363. The circuit is equipped with control pin that can set the amplifier to low
current-low noise mode or to high current-high linearity mode and/or disable (off) mode. This
report describes an application in which the LNA can be tuned for gain and input IP3. At 900
Mhz, the input IP3 is adjustable between 2 dBm at 19 dB gain and 7 dBm at 16 dB gain.
H
Circuit description
The LNA consists of one RF stage. The RF transistor is biased with a controlled bias circuit that
can set the collector current of RF transistor to the desired value. The trade-off between
noise/linearity and current consumption can be found by setting the collector current of RF
transistor. In this way it is possible to make a low noise mode and a high linearity mode.
Moreover, the control pin serves as an enable/disable pin that can switch the supply current off.
In order to increase the linearity of LNA, a series feedback has to be introduced, made by
stripline, from the emitter of the RF transistor to ground.
Measured results
conditions:
demo board without u-stripline (0 mm)
freq=900 MHz; Vsupply= 3V; temp=25 deg
Vc
Isupply
S21
Input return loss
Output return loss
IIP3
NF
Pout1db compression
[V]
1.0
1.4
1.6
1.9
2.3
2.7
3.0
[mA]
1.4
3.5
4.6
6.5
11.1
13.9
15.5
[dB]
11.9
16.6
17.5
18.3
19.0
19.1
19.2
[dB]
4.3
8.7
10.0
11.1
11.3
11.2
11.2
[dB]
5.4
8.1
8.9
10.2
11.4
11.8
12.0
[dBm]
-21
-9
-6
-5
+2
+3
+4
[dB]
1.1
1.3
1.3
1.4
1.5
1.6
1.7
[dBm]
-17
-9
-6
-2
+3
+6
+7
conditions:
demo board with 1.5 mm u-stripline
freq=900 MHz; Vsupply= 3V; temp=25 deg
Vc
Isupply
S21
Input return loss
Output return loss
IIP3
NF
Pout1db compression
[V]
1.0
1.4
1.6
1.9
2.3
2.7
3.0
[mA]
1.4
3.5
4.6
6.5
11.1
13.9
15.5
[dB]
10.3
13.8
14.4
15.1
15.7
15.8
15.8
[dB]
6.9
14.6
18.0
21
18.6
17.7
17.4
[dB]
6.8
9.5
10.4
11.3
12.7
13.0
13.1
[dBm]
-9
-2
+1
+4
+7
+8
+8
[dB]
1.1
1.4
1.4
1.5
1.6
1.7
1.8
[dBm]
-16
-7
-5
-2
+4
+7
+8
note:
IIP3 - input IP3 measured with ∆f=100 kHz and Pin<-28 dBm
Isupply - is a total supply current from 3 Volt supply source
2
H
Application diagram
Vc
C5
C3
C4
Vc
C6
Vs
L2
Vs
Bias
Circuit
L1
RFoutput
Out
RFinput
In
C2
C1
SOT363
gnd
u-strip
0-1.5 mm
C6
u-stripline
L1
C1
C2
x
C4
L2
x
x
C3
C5
<-------20mm------->
<-------20mm------->
Demo board
Component
C1
C2
C3
C4
C5
C6
L1
L2
Value
Typ
100 pF
Philips 0603
100 pF
Philips 0603
22 nF
Philips 0603
5.6 pF
Philips 0603
22 nF
Philips 0603
2x 100 nF Philips 0805
10 nH
TDK 0603
8.2 nH
TDK 0603
notes:
1. There are 4 types of demo board layouts
available: no stripline (0 mm), 0.5 mm, 1.0
mm and 1.5 mm stripline; marked L0,
L05, L10 and L15.
2. The u-stripline to ground is optimized for
each length.
For no stripline (0 mm), the metal under
pin 5 and 6 is filled with vias to the
ground plane to reduce inductance.
For the stripline versions, the stripline
ends in 2 vias.
3. The standard demo board also needs three
0 Ù SMD’s (0603) at the spots marked
with an X. Additional components to
adjust the biasing can be placed at these
spots.
3
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