AN075

A pp l ic a t io n N o t e, R e v . 2. 0 , J a n. 2 00 7
A p p li c a t i o n N o t e N o . 0 7 5
H i g h T h i r d- O r d e r I n p u t I n te r c e p t P o i n t C D M A 8 0 0
Low Noise Amplifier
R F & P r o t e c ti o n D e v i c e s
Edition 2007-01-08
Published by
Infineon Technologies AG
81726 München, Germany
© Infineon Technologies AG 2009.
All Rights Reserved.
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THIRD PARTY) WITH RESPECT TO ANY AND ALL INFORMATION GIVEN IN THIS APPLICATION NOTE.
Information
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Application Note No. 075
Application Note No. 075
Revision History: 2007-01-08, Rev. 2.0
Previous Version: 2002-08-05
Page
Subjects (major changes since last revision)
All
Document layout change
Application Note
3
Rev. 2.0, 2007-01-08
Application Note No. 075
High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier
High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier
Features
• Extremely high IIP3 of 10 dB at 850 MHz associated with a low
current consumption
• High overall performance at extraordinarily low cost
2
3
1
Introduction
The BFR380F is a silicon bipolar transistor housed in a small outline TSFP-3 package. The BFR380F is a member
of Infineon’s new 3+ generation transistor family consisting of three different sizes of transistors: BFR340F,
BFR360F and BFR380F. These transistors are 14 GHz transition-frequency devices which take advantage of the
latest manufacturing techniques requiring fewer processing steps than other devices in their class, thereby offering
excellent performance and device-to-device consistency at extraordinarily low cost. All types of 3+ transistors are
also available in Infineon’s new TSLP-3 package. The world’s smallest chip size leadless plastic package for
discrete components like diodes and transistors.
With a noise figure of 1.1 dB at 1800 MHz and a bias point of 3 V / 8 mA, the BFR380F is a good solution for costsensitive LNA designs. In addition, the BFR380F is an ideal choice for VCO applications due to its low flicker noise
corner frequency of 15 kHz.
This application note describes the BFR380F as a CDMA 800 LNA for the frequency range between 830 MHz and
870 MHz. Table 1 shows the measured performance of the application circuit. All parameters include losses of
PCB and SMA connectors.
Table 1
Measured Performance at 850 MHz
Parameter
Value
Unit
Supply voltage
3
V
Supply current
8.2
mA
Gain
14.8
dB
1.1
dB
Input 3 order intercept point
10.5
dBm
Input return loss
14.4
dB
Output return loss
18.1
dB
Reverse isolation
20.2
dB
Input compression point
-9
dB
Noise figure
rd
1)
1) ∆f = 1 MHz, -25 dBm per tone
Application Note
4
Rev. 2.0, 2007-01-08
Application Note No. 075
High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier
Application Circuit
Figure 1 shows the schematic of the application circuit. Input IP3 is improved by different measures. The first one
is inductive emitter degeneration where a microstrip line between emitter and ground enlarges the emitter
inductance. This additional emitter feedback decreases gain and increases input IP3 in about the same magnitude
while output IP3 remains at the same level. As a drawback increased emitter inductance destabilizes the device
at higher frequencies so a careful look at the circuit’s stability factor is necessary when applying emitter
degeneration.
Another possibility to increase IP3 on the whole is to provide low frequency paths to ground at base and collector
to avoid AM modulation effects. At the base L1 and C1 form such a path at the transistor’s base, the one at the
collector consists of L2-R3-C3. In general the low frequency path at the base is the more efficient way to increase
IP3. For more detailed information on increasing IP3 by low frequency grounding please refer to Infineon’s
application note AN060 (BFP620) and AN057 (BFP540).
Vcc
R1
10Ω
C1
100nF
C3
100nF
R2
33kΩ
R3
2.2Ω
L1
5.6nH
L2
4.7nH
C4
6.8pF
RFin
C2
10pF
R4
0Ω
RFout
Q1
BFR380F
Inductive Emitter Degeneration (Microstrip):
L = 1 mm, W = 0.2 mm
AN075_schematic_diagram.vsd
Figure 1
Schematic Diagram
Table 2
Bill of Materials
Name
Value
Package
Manufacturer
Function
C1
100 nF
0603
Various
RF decoupling, IP3 improvement
C2
10 pF
0402
Various
Input matching, DC block
C3
100 pF
0603
Various
RF decoupling, IP3 improvement
C4
6.8 pF
0402
Various
Output matching, DC block
L1
5.6 nH
0402
Toko LL 1005-FH RF Choke, input matching
L2
4.7 nH
0402
Toko LL 1005-FH RF Choke, output matching
Q1
BFR380F
TSFP-3
Infineon
Si BJT
R1
10 Ω
0402
Various
Biasing
R2
33 Ω
0402
Various
Biasing
Application Note
5
Rev. 2.0, 2007-01-08
Application Note No. 075
High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier
Table 2
Bill of Materials (cont’d)
Name
Value
Package
Manufacturer
Function
R3
2.2 Ω
0402
Various
Stability
R4
0Ω
0402
Various
Jumper
Vcc
L2
Q1
NA
C1
L1
NA
10 mm
NA
NA
In
R3
R2
C2
C3
R1
12 mm
C4
R4
Out
AN075_placement_on_PCB.vsd
Figure 2
Component placement on PCB
0.2 mm FR4
35 µm Cu
35 µm Cu
for mechanical
rigidity of PCB
0.8 mm FR4
35 µm Cu
AN075_PCB _cross_section.vsd
Figure 3
PCB Cross Section
Evaluation boards for the LNA depicted in this application note are available from Infineon Technologies.
Application Note
6
Rev. 2.0, 2007-01-08
Application Note No. 075
High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier
Measured Curves
The following pages show measurement graphs of the BFR380F LNA described in this application note. As
mentioned before all measurement results presented here include losses of PCB and connectors, in other words.
the reference plane is at the SMA connectors.
16
Gain [dB]
15.5
15
14.5
14
13.5
13
0.83
0.84
0.85
0.86
0.87
Frequency [GHz]
AN075_Gain(f).vsd
Figure 4
Measured Gain
1.5
Noise Figure [dB]
1.4
1.3
1.2
1.1
1
0.9
0.8
0.83
0.84
0.85
Frequency [GHz]
Figure 5
0.86
0.87
AN075_NF(f).vsd
Measured Noise Figure
Application Note
7
Rev. 2.0, 2007-01-08
Application Note No. 075
High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier
10
Return Loss [dB]
12
14
s11
16
s22
18
20
22
0.83
0.84
0.85
0.86
0.87
Frequency [GHz]
AN075_Return_loss(f).vsd
Figure 6
Measured In- and Output Return Loss
Reverse Isolation [dB]
17
18
19
20
21
22
23
0.83
0.84
0.85
Frequeny [GHz]
Figure 7
0.86
0.87
AN075_Reverse_isolation(f).vsd
Measured Reverse Isolation
Application Note
8
Rev. 2.0, 2007-01-08
Application Note No. 075
High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier
17
5
16
15
-5
Gain
14
-10
P out
-15
Gain [dB]
P out [dBm]
0
13
-20
12
-35
-30
-25
-20
-15
-10
-5
P in [dBm]
AN075_Pout_Gain(Pin).vsd
Figure 8
Measured Gain Compression
5
K, B1
4
3
2
K
1
B1
0
0
1
2
3
Frequency [GHz]
Figure 9
4
5
6
A N075_K_B1(f).vsd
Measured Stability Factor K and Stability Measured B1
Application Note
9
Rev. 2.0, 2007-01-08
Application Note No. 075
High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier
18
16
Gain [dB]
14
12
10
8
6
4
2
0
0
1
2
3
4
Frequency [GHz]
Figure 10
5
6
AN075_GainWS(f).vsd
Measured Gain - Wide Span
0
Return Loss [dB]
5
s11
10
15
s22
20
25
30
0
1
2
3
4
5
6
Frequency [GHz]
AN075_Return_lossWS(f).vsd
Figure 11
Measured Return Loss - Wide Span
Application Note
10
Rev. 2.0, 2007-01-08