AN126 - BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage Low Noise Amplifier (LNA), with reduced external component count and reduced gain at 2.4 GHz

Application Note, Rev. 1.2, Oktober 2007
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium
Transistor as 5 -6 GHz Single-Stage Low Noise
Amplifier (LNA), with reduced external component
count and reduced gain at 2.4 GHz
RF & Protection Devices
Edition 2007-10-17
Published by
Infineon Technologies AG
81726 München, Germany
© Infineon Technologies AG 2010.
All Rights Reserved.
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Application Note No. 126
Application Note No. 126
Revision History: 2007-10-17, Rev. 1.2
Previous Version: 2005-04-14, Rev. 1.1
Page
Subjects (major changes since last revision)
All
Small changes in figure descriptions
Application Note
3
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
1
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz
Single-Stage Low Noise Amplifier (LNA), with reduced external
component count and reduced gain at 2.4 GHz
Overview
•
•
The Silicon-Germanium BFP640F in TSFP-4 package is shown in a modified 5 - 6 GHz LNA circuit derived
from the BFP640 application shown in Applications Note AN082 (attached). This modified circuit is targeted
for WLAN module manufacturers and reduces external component count to the absolute minimum. Note some
performance is sacrificed to achieve reduced component count, most notably third-order intercept
performance. Please also note, an attempt was made to reduce out-of-band gain, specifically to reduce gain
at 2.4 GHz per customer request.
In order to preserve input & output impedance match with reduced component count, a "trick" was used:
DC blocking capacitors had their values increased such that they are used above their "self-resonant
frequency" (SRF). C1 changes from 1.5 to 5.6 pF, C2 changes from 1.5 to 12 pF. Doing this makes these
capacitors show some slight net inductive reactance in the 5 GHz frequency range, as opposed to these
capacitors either appearing as a straight "short" or a capacitive reactance. The chip capacitors can be modeled
as a series R-L-C with the capacitor's self-inductance being on the order of 0.5 nH. By using the chip's selfinductance, one can tailor the reactance of the chip capacitor by selecting the appropriate value of
capacitance, and the R-L-C combination can be made to have resonance above the frequency of interest
(normal case) or below the frequency of interest (done here in this "Trick").
Table 1
Comparison of Component Count for Original and Modified Circuits, for Single LNA Stage
Component Type
Number in Original
Circuit
Number in Modified
Circuit (new)
Comments
Chip Capacitor
6
3
C3, C4, C6 eliminated
Chip Resistor
3
3
Chip Inductor
3
1
•
•
L1, L3 eliminated
3 capacitors, 2 inductors have been eliminated, reducing external components from 12 pieces to 7 pieces.
Please refer to schematic diagrams on page 4.
Note gain at 2.4 GHz has been reduced from ≈ 15 dB to ≈ 8 dB (e.g. 7 dB gain reduction in 2.4 GHz range with
this new, reduced parts count design).
Applications
•
•
•
Wireless LAN (802.11a)
Cordless Telephones (5.8 GHz)
Other 5 -6 GHz systems
Application Note
4
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Summary
Achieved ≅ 10 dB gain, 1.3 dB Noise Figure over the 4900 - 6000 MHz band, drawing 8.9 mA @ 3 V. Input 3rd
Order Intercept = +8.7 dBm. Output P1dB = +6.9 dBm. Total external component count (L, C, R) has been reduced
from 12 pieces to 7 pieces. Please note noise figure result does not extract PC board losses, if PCB loss were
extracted, noise figure result would improve by approximately 0.2 - 0.3 dB (e.g. if loss is extracted, noise figure
would be 1.1 to 1.3 dB).
Cross Sectional Diagram of PC Board
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PCB - Cross Sectional Diagram
Application Note
5
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Summary of Data
T = 25 °C, network analyzer source power = -30 dBm
Table 2
Summary of Data
Parameter
Result
Frequency Range
Under 4.9 - 6 GHz
DC Current
8.9 mA @ 3.0 V supply voltage
(VCE = 2.7 V)
Note power supply voltage is
measured directly across PCB supply
line and ground, to eliminate voltage
drop across wire harness
Gain
11.0 dB @ 4900 MHz
10.1 dB @ 5500 MHz
9.7 dB @ 6000 MHz
Gain at 5150 MHz = 10.7 dB
Noise Figure
1.3 dB @ 4900 MHz
1.4 dB @ 5500 MHz
1.5 dB @ 6000 MHz
These values do NOT extract PCB
losses, etc. resulting from FR4 board
and passives used on PCB - these
results are at input SMA connector
Input P1dB
-2.2 dBm @ 5500 MHz
Output P1dB
+6.9 dBm @ 5500 MHz
rd
Comments
Input 3 Order Intercept
+8.7 dBm @ 5150 MHz
Output 3rd Order Intercept
+19.4 dBm @ 5150 MHz
Input Return Loss
9.3 dB @ 4900 MHz
11.6 dB @ 5500 MHz
14.0 dB @ 6000 MHz
Output Return Loss
10.4 dB @ 4900 MHz
11.9 dB @ 5500 MHz
12.7 dB @ 6000 MHz
Reverse Isolation
17.7 dB @ 4900 MHz
16.4 dB @ 5500 MHz
15.5 dB @ 6000 MHz
Application Note
6
Figure 16 and Figure 17. IP3 could
be improved by 6 to 10 dB by putting
L1 and C3 back into the circuit.
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Schematic Diagram, Original Circuit
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Figure 2
Schematic Diagram
Application Note
7
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Schematic Diagram, NEW Circuit with Reduced Parts Count
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Figure 3
Schematic Diagram
Application Note
8
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Details on TSFP-4 Package (“Thin Small Flat Pack”). Dimensions in millimeters (mm).
0.2 ±0.05
3
1
1.2 ±0.05
0.2 ±0.05
4
0.55 ±0.04
2
0.2 ±0.05
10˚ MAX.
0.8 ±0.05
1.4 ±0.05
0.15 ±0.05
0.5 ±0.05
0.5 ±0.05
Figure 4
GPX01010
Package Details of TSFP-4
Recommended Soldering Footprint for TSFP-4 (dimensions in millimeters).
Device package is to be oriented as shown in above drawing (e.g. orient long package dimension horizontally on
this footprint).
0.9
0.45
0.35
0.5
0.5
HLGF1011
Figure 5
Package Footprint of TSFP-4
Application Note
9
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Noise Figure, Plot, 4.5 GHz to 6.5 GHz. Center of Plot (x-axis) is 5.5 GHz.
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Figure 6
Noise Figure
Application Note
10
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Noise Figure, Tabular Data
From Rhode & Schwarz FSEK3 + FSEM30 + System PreAmp
Table 3
Noise Figure
Frequency
Noise Figure
4500 MHz
1.17 dB
4550 MHz
1.27 dB
4600 MHz
1.27 dB
4650 MHz
1.29 dB
4700 MHz
1.29 dB
4750 MHz
1.28 dB
4800 MHz
1.28 dB
4850 MHz
1.30 dB
4900 MHz
1.31 dB
4950 MHz
1.32 dB
5000 MHz
1.32 dB
5050 MHz
1.35 dB
5100 MHz
1.37 dB
5150 MHz
1.35 dB
5200 MHz
1.39 dB
5250 MHz
1.40 dB
5300 MHz
1.39 dB
5350 MHz
1.35 dB
5400 MHz
1.35 dB
5450 MHz
1.37 dB
5500 MHz
1.37 dB
5550 MHz
1.33 dB
5600 MHz
1.32 dB
5650 MHz
1.34 dB
5700 MHz
1.34 dB
5750 MHz
1.34 dB
5800 MHz
1.38 dB
5850 MHz
1.38 dB
5900 MHz
1.39 dB
5950 MHz
1.43 dB
6000 MHz
1.45 dB
6050 MHz
1.49 dB
6100 MHz
1.56 dB
6150 MHz
1.63 dB
6200 MHz
1.69 dB
6250 MHz
1.61 dB
6300 MHz
1.56 dB
6350 MHz
1.51 dB
Application Note
11
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Table 3
Noise Figure (cont’d)
Frequency
Noise Figure
6400 MHz
1.48 dB
6450 MHz
1.46 dB
6500 MHz
1.47 dB
Application Note
12
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Scanned Image of PC Board
Figure 7
Image of PC Board
Application Note
13
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Scanned Image of PC Board, Close-In Shot
Total PCB area used ≅ 40 mm²
Figure 8
Image of PC Board, Close-In Shot
Application Note
14
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Stability
Rohde and Schwarz ZVC Network Analyzer calculates and plots Stabilty Factor "K" in real time, from 5 MHz to
8 GHz. Note K>1 over entire range except at ≈ 260 MHz. Further work is needed to bring K>1 here. Suggest
varying / tuning value of resistor R1 to improve K in 260 MHz range, or putting capacitor C6 back into the circuit,
in order to improve "K" at low frequencies.
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Plot of K(f)
Application Note
15
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Gain Compression at 5500 MHz
Amplifier is checked for 1 dB compression point at VCC = 3.0 V, IC = 8.9 mA (with VCE = 2.7 V). An Agilent power
meter was used to ensure accurate power levels are measured (as opposed to using Vector Network Analyzer in
"Power Sweep" mode).
Input P1dB ≅ -2.2 dBm
Output P1dB ≅ -2.2 dBm + (Gain - 1 dB) = -2.2 dBm + (10.1 - 1) dB = +6.9 dBm
Table 4
Gain Compression
Pin, dBm
Pout, dBm
Gain
-11.0
-0.9
10.1
-10.0
+0.1
10.1
-9.0
+1.0
10.0
-8.0
+2.0
10.0
-7.0
+2.9
9.9
-6.0
+3.8
9.8
-5.0
+4.7
9.7
-4.0
+5.6
9.6
-3.0
+6.4
9.4
-2.0
+7.0
9.0
-1.0
+7.6
8.6
0.0
+8.1
8.1
Application Note
16
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
PLEASE NOTE - all plots are taken from Rohde And Schwarz ZVC Network Analyzer
Input Return Loss, Log Mag
5 MHz to 8 GHz Sweep
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Plot of Input Return Loss
Application Note
17
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Input Return Loss, Smith Chart
Reference Plane = Input SMA Connector on PC Board
5 MHz to 8 GHz Sweep
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Smith Chart of Input Return Loss
Application Note
18
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Forward Gain
5 MHz to8 GHz Sweep
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Plot of Forward Gain
Application Note
19
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Reverse Isolation
5 MHz to 8 GHz Sweep
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Application Note
20
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Output Return Loss, Log Mag
5 MHz to 8 GHz Sweep
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Plot of Output Return Loss
Application Note
21
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Output Return Loss, Smith Chart
Reference Plane = Output SMA Connector on PC Board
5 MHz to 8 GHz Sweep
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Smith Chart of Output Return Loss
Application Note
22
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
Input Stimulus for Amplifier Two-Tone Test
f1 = 5150 MHz, f2 = 5151 MHz, -23 dBm each tone.
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Figure 16
Tow-Tone Test, Input Stimulus
Application Note
23
Rev. 1.2, 2007-10-17
Application Note No. 126
BFP640F Low-Noise Silicon-Germanium Transistor as 5 -6 GHz Single-Stage
LNA Response to Two-Tone Test
Input IP3 = -23 + (63.3/2) = +8.7 dBm
Output IP3 = +8.7 dBm + 10.7 dB gain = + 19.4 dBm
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Figure 17
Tow-Tone Test, LNA Response
Application Note
24
Rev. 1.2, 2007-10-17
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