AN171

Application Note, Rev. 1.1, January 2009
Application Note No. 171
BFP740F SiGe:C Ultra Low Noise RF Transistor in
2.4 – 2.5 GHz LNA Application with 17 dB Gain, 0.7 dB
Noise Figure & < 1 microsecond Turn-On / Turn-Off Time
(For 802.11b/g & 802.11n “MIMO” Wireless LAN Applications)
Small Signal Discretes
Never stop thinking
Edition 2009-01-23
Published by
Infineon Technologies AG
81726 München, Germany
© Infineon Technologies AG 2009.
All Rights Reserved.
LEGAL DISCLAIMER
THE INFORMATION GIVEN IN THIS APPLICATION NOTE IS GIVEN AS A HINT FOR THE
IMPLEMENTATION OF THE INFINEON TECHNOLOGIES COMPONENT ONLY AND SHALL
NOT BE REGARDED AS ANY DESCRIPTION OR WARRANTY OF A CERTAIN
FUNCTIONALITY, CONDITION OR QUALITY OF THE INFINEON TECHNOLOGIES
COMPONENT. THE RECIPIENT OF THIS APPLICATION NOTE MUST VERIFY ANY
FUNCTION DESCRIBED HEREIN IN THE REAL APPLICATION. INFINEON TECHNOLOGIES
HEREBY DISCLAIMS ANY AND ALL WARRANTIES AND LIABILITIES OF ANY KIND
(INCLUDING WITHOUT LIMITATION WARRANTIES OF NON-INFRINGEMENT OF
INTELLECTUAL PROPERTY RIGHTS OF ANY THIRD-PARTY) WITH RESPECT TO ANY AND
ALL INFORMATION GIVEN IN THIS APPLICATION NOTE.
Information
For further information on technology, delivery terms and conditions and prices please contact
your nearest Infineon Technologies Office (www.infineon.com).
Warnings
Due to technical requirements components may contain dangerous substances. For information
on the types in question please contact your nearest Infineon Technologies Office.
Infineon Technologies Components may only be used in life-support devices or systems with the
express written approval of Infineon Technologies, if a failure of such components can reasonably
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If they fail, it is reasonable to assume that the health of the user or other persons may be
endangered.
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Application Note No. 171
Revision History: 2009-01-23, Rev 1.1
2009-01-22, Rev 1.0
Changes to previous version (1.0 => 1.1):
Page 4
Cleanup of text
Page 6
Revised schematic diagram
Page 25
Addition of references [2] and [3]
Page 16
Correction to text
Trademarks
SIEGET® is a registered trademark of Infineon Technologies AG.
Additional Information:
More details about Infineon RF Transistors may be found at www.infineon.com/RF
Direct link to RF Transistor Datasheets / Specifications: www.infineon.com/rf.specs
For S-Parameters, Noise Parameters, SPICE models: www.infineon.com/rf.models
For Application Notes: www.infineon.com/rf.appnotes
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
1
BFP740F SiGe:C Ultra Low Noise RF Transistor in 2.4 – 2.5 GHz LNA
Application with 17 dB Gain, 0.7 dB Noise Figure & < 1 microsecond
Turn-On / Turn-Off Time
Overview
• Infineon Technologies BFP740F is a high gain, ultra low noise Silicon-Germanium-Carbon
(SiGe:C) HBT device suitable for a wide range of Low Noise Amplifier (LNA) applications.
Refer to Reference [1], BFP740F datasheet, embedded on page 25 of this document.
2
•
The circuit shown is targeted for 802.11b / g & 802.11n “MIMO” applications in the Wireless
Local Area Network (WLAN) market, particularly for Access Points (AP’s) which require
external LNA’s to fulfill high-sensitivity / long range requirements. LNA’s for this application
must be able to switch on / off within about 1 microsecond (1000 nanoseconds). The charge
storage (capacitance) used in this circuit is minimized to reduce on / off times. Trade-off for
reduced capacitance values is a reduction in Third Order Intercept (IP3) performance. Inductive
emitter degeneration is used to improve amplifier low-frequency stability and impedance
matching. Refer to Reference [2] for a general overview of charge storage and inductive
emitter degeneration. Amplifier is Unconditionally Stable (µ1 > 1.0) from 10 MHz – 12 GHz.
•
External parts count (not including BFP740F transistor) = 10; 5 capacitors, 3 resistors, and 2
chip inductors. All passives are ‘0402’ case size. BFP740F transistor package is RoHS –
compliant and measures 1.4 x 1.2 x 0.55mm.
Summary Of Performance Data
(T=25 °C, network analyzer source power ≈ -25 dBm, VCC = 3.0 V, VCE = 2.3 V, IC=14.7 mA, ZS=ZL=50 Ω )
Frequency
* NF IIP3 OIP3 IP1dB OP1dB
MHz
dB[s11]2 dB[s21]2 dB[s12]2 dB[s22]2 dB dBm dBm dBm dBm
- 10.5
-27.9
-9.7
--------2400
17.5
0.7
-10.3
-27.8
-10.1
2441
17.4
0.8 -3.2 +14.2 -13.1 +3.1
-10.1
-27.7
-10.7
--------2483.5
17.3
0.7
* does not extract PCB loss. If PCB loss (at input) were extracted, noise figure would be ~ 0.1 dB lower.
Turn-On Time: ~ 480 nanoseconds; Turn-Off Time ~ 32 nanoseconds. Please refer to pages 24 – 25.
Note: reverse isolation ( dB[s12]2 ) when DC power to LNA is OFF = -18.8 dB @ 2441 MHz.
3
Details of PC Board Construction
PC board uses standard, low-cost “FR4” glass-epoxy material. A cross-section diagram of the PC board
is given below. The “Gerber” & other fabrication files used for the generation of the PC board shown in
this app note are embedded in the “References” section of this Applications Note on page 25. [3]
PCB CROSS SECTION
0.012 inch / 0.305 mm
TOP LAYER
INTERNAL GROUND PLANE
0.028 inch / 0.711 mm ?
LAYER FOR MECHANICAL RIGIDITY OF PCB, THICKNESS HERE NOT CRITICAL AS
LONG AS TOTAL PCB THICKNESS DOES NOT EXCEED 0.045 INCH / 1.14 mm
(SPECIFICATION FOR TOTAL PCB THICKNESS: 0.040 + 0.005 / - 0.005 INCH;
1.016 + 0.127 mm / - 0.127 mm )
BOTTOM LAYER
Application Note
4 / 25
Rev. 1.1 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
4
TSFP-4 Package Outline and Footprint
(Dimensions in millimeters). Note maximum package height is 0.59 mm / 0.023 inch.
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).
Application Note
5 / 25
Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
5
Schematic Diagram
Inductors are Murata LQP15M Series
(formerly LQP10A) 0402 case size.
Capacitors and resistors are 0402 case size.
J3
DC Connector
V
cc
= 3.0 V
PCB = 740F-080930 Rev A
PC Board Material = Standard FR4
I = 14.7 mA
= 50 ohm microstripline
10 external passives used:
5 capacitors
2 inductors
3 resistors
R2
36K
C2
8.2pF
R3
39 ohms
C4
33pF
R1
10 ohms
L1
9.1nH
J1
RF
INPUT
C1
33pF
C5
2.2pF
L2
Q1
4.3nH
BFP740F
SiGe:C
Transistor
J2
C3
2.2pF
RF OUTPUT
Q1: VCE = 2.3 V
W
L
Inductive Emitter Degeneration for low frequency stability improvement, impedance matching.
One identical microstrip track from each of the two emitter leads to a separate ground via hole
is used. Ground hole via diameter is 0.012 inch / 0.3mm. Microstrip inductor dimensions are:
W = 0.010 inch / 0.25 mm; L = 0.023 inch / 0.584 mm, height “h” between top layer RF traces and
internal ground plane is 0.012 inch / 0.3mm. Note if spacing in the user’s PCB between top
layer RF traces and internal ground plane is substantially greater than 0.012 inch / 0.3 mm, e.g.
0.062 inch / 1.6 mm thick, the additional via hole inductance of the thicker PCB will suffice by
itself, and the microstrip inductors can be eliminated entirely. Note PCB “Gerber” fabrication
files for the application board shown are attached in the “References” section on page 25 of
this Applications Note.
Application Note
6 / 25
Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
6
Bill Of Material (BOM)
Reference
Designator
Value
C1
33pF
‘0402’ chip capacitor
Various
C2
C3
8.2pF
2.2pF
‘0402’ chip capacitor
‘0402’ chip capacitor
Various
Various
C4
C5
33pF
2.2pF
‘0402’ chip capacitor
‘0402’ chip capacitor
Various
Various
L1
9.1nH
‘0402’ case size chip inductor
Murata LQP15M Series or equivalent
Murata
L2
4.3nH
‘0402’ case size chip inductor
Murata LQP15M series or equivalent
Murata
R1
R2
R3
10 Ω
36KΩ
39Ω
‘0402’ chip resistor
‘0402’ chip resistor
‘0402’ chip resistor
Various
Various
Various
Q1
---
J1, J2
J3
---
Application Note
Description / Part #
Manufacturer
BFP740F SiGe:C Low Noise RF
Transistor, TSFP-4 package
Infineon
Technologies
RF Edge Mount SMA Female Connector,
142-0701-841
MTA-100 Series 5 pin connector
640456-5
PC Board, Part # 740F-080930 Rev A
7 / 25
Function
Input DC block; also using cap
above
Self-Resonant
Frequency makes it have some
net inductive reactance at 2.4
GHz to slightly improve input
match
RF Decoupling / blocking cap
Output
DC
block;
also
influences output and input
match
RF decoupling / blocking cap
RF decoupling / blocking cap;
also influences output match
and amplifier stability margin
RF Choke at LNA input (for DC
bias to base). Also has some
influence on input match due to
relatively low value
RF ‘Choke’ at LNA output, for
DC bias to collector.
Also
influences
matching
and
stability.
For RF stability improvement.
DC biasing (base current).
DC biasing (provides DC
negative feedback to stabilize
DC operating point over
temperature
variation,
transistor hFE variation, etc.)
LNA active device.
Emerson /
Johnson
Tyco (AMP)
Input, Output RF connector
Infineon
Technologies
Printed Circuit Board
5 Pin DC connector header
Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
7
Scanned Images of PC Board
View of Entire PC Board
Application Note
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Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Close-In View of LNA Section
Application Note
9 / 25
Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
8
Noise Figure Measurement Data
Noise Figure Plot, from Rohde and Schwarz FSEK3 + FSEM30
Rohde & Schwarz FSEK3
22 Jan 2009
Noise Figure Measurement
EUT Name:
Manufacturer:
Operating Conditions:
Operator Name:
Test Specification:
Comment:
BFP740F 2.4 - 2.5 GHz LNA, Fast Switching / Fast Turn ON-OFF Time
Infineon Technologies
T=25 C, V = 3.0V, Vce = 2.3V, I = 14.7mA
Gerard Wevers
WLAN 802.11b/g and 802.11n
PCB = 740F-080930 Rev A; Preamp = MITEQ SMC-02
22 Jan 2008
Analyzer
RF Att:
Ref Lvl:
0.00 dB
-50.00 dBm
RBW :
VBW :
1 MHz
100 Hz
Range: 30.00 dB
Ref Lvl auto: ON
Measurement
2nd stage corr: ON
Mode: Direct
ENR: 346A_1.ENR
Noise Figure /dB
1.30
1.20
1.10
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
2300 MHz
Application Note
30 MHz / DIV
10/ 25
2600 MHz
Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Noise Figure, Tabular Data
Taken With Rohde & Schwarz FSEM30 + FSEK3
System Preamplifier = MITEQ SMC-02
Frequency
2300 MHz
2310 MHz
2320 MHz
2330 MHz
2340 MHz
2350 MHz
2360 MHz
2370 MHz
2380 MHz
2390 MHz
2400 MHz
2410 MHz
2420 MHz
2430 MHz
2440 MHz
2450 MHz
2460 MHz
2470 MHz
2480 MHz
2490 MHz
2500 MHz
2510 MHz
2520 MHz
2530 MHz
2540 MHz
2550 MHz
2560 MHz
2570 MHz
2580 MHz
2590 MHz
2600 MHz
Application Note
Nf
0.70 dB
0.68 dB
0.66 dB
0.69 dB
0.66 dB
0.65 dB
0.70 dB
0.68 dB
0.69 dB
0.69 dB
0.66 dB
0.68 dB
0.69 dB
0.68 dB
0.75 dB
0.63 dB
0.70 dB
0.64 dB
0.68 dB
0.69 dB
0.69 dB
0.70 dB
0.67 dB
0.66 dB
0.69 dB
0.67 dB
0.71 dB
0.69 dB
0.68 dB
0.70 dB
0.71 dB
11/ 25
Temp
50.6 K
48.8 K
47.2 K
50.3 K
47.7 K
46.9 K
50.6 K
49.4 K
49.6 K
49.7 K
47.2 K
49.4 K
49.7 K
49.1 K
54.3 K
45.1 K
50.7 K
46.2 K
49.4 K
50 K
49.8 K
50.7 K
48.7 K
47.3 K
50.2 K
48.6 K
51.2 K
49.9 K
49.1 K
50.3 K
51.2 K
Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
9
Amplifier Compression Point Measurement
Gain Compression at 2441 MHz, VCC = +3.0 V, I = 14.7mA, VCE = 2.3V, T = 25°C:
ZVB20 Vector Network Analyzer is set up to sweep input power to LNA in a “Power Sweep” at a
fixed frequency of 2441 MHz. ZVB20 Port 1, which provides INPUT power to drive the LNA, has
its power level calibrated (“SOURCE POWER CAL”) with the NRP-Z21 power sensor to ensure
power level accuracy with the reference plane at the RF input connector of the amplifier. X-axis
of VNA screen-shot below shows input power to LNA swept from –30 to –5 dBm.
Input 1 dB compression point = - 13.1 dBm
Output 1dB compression point = -13.1 dBm + (Gain–1dB) = -13.1 dBm + 16.2 dB = +3.1 dBm
Trc1 S21 dB Mag 3 dB / Ref 0 dB
Cal Off PCax Smo Offs
1
M 1 -33.16 dBm
• M 2 -13.08 dBm
S21
M1
18
17.249 dB
16.249 dB
M2
15
12
9
6
3
0
-3
-6
Ch1
Start -35 dBm
Freq 2.441 GHz
Stop -5 dBm
1/22/2009,8:25 AM
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Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
10
Amplifier Stability, Gain, Return Loss and Reverse Isolation Plots
Amplifier Stability - Plot of Stability Factor “
µ”:
1
Rohde and Schwarz ZVB Network Analyzer Calculates and plots stability factor “µ1” of the BFP740F
amplifier in real time. Stability Factor µ1 is defined as follows [1]:
µ
1 - |S11|2
1
=
| S22 – S11* det(S) | + |S21S12|
The necessary and sufficient condition for Unconditional Stability is µ1 > 1.0. In the plot, µ1 > 1.0
over 10 MHz – 12 GHz; amplifier is Unconditionally Stable over 10 MHz – 12 GHz frequency range.
Trc1 µ1 Lin Mag 100 mU/ Ref 1.2 U
Cal Smo Offs
1
• M 1 2.400000 GHz 1.3556 U
M 2 2.441000 GHz 1.3732 U
M 3 2.483500 GHz 1.3983 U
µ1
1600.0
1500.0
M3
1400.0
M1
2
M
1300.0
1200.0
1100.0
1000.0
900.0
800.0
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/22/2009,8:11 AM
[1]. “Fundamentals of Vector Network Analysis”, Michael Hiebel, 4th edition 2008, pages 175 – 177, ISBN
978-3-939837-06-0
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Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Input Return Loss, Log Mag
10 MHz – 12 GHz Sweep
Trc1 S11 dB Mag 5 dB / Ref 0 dB
Cal Smo Offs
1
• M 1 2.400000 GHz -10.488 dB
M 2 2.441000 GHz -10.272 dB
M 3 2.483500 GHz -10.111 dB
S11
15
10
5
0
-5
M1
M
23
M
-10
-15
-20
-25
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/22/2009,8:06 AM
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Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Input Return Loss, Smith Chart
Reference Plane = Input SMA Connector on PC Board
10 MHz – 12 GHz Sweep
Trc1 S11 Smith
Ref 1 U
Cal Smo Offs
1
1
S11
26.889
j1.3158
87.257
2
M 2 2.441000 GHz 26.434
j1.5808
103.07
M 3 2.483500 GHz 26.292
j2.2332
5
143.12
• M 1 2.400000 GHz
0.5
Ω
Ω
pH
Ω
Ω
pH
Ω
Ω
pH
M
M321
0
0.2
0.5
1
2
5
-5
-0.5
-2
-1
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/22/2009,8:07 AM
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Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Forward Gain.
10 MHz – 12 GHz Sweep
Trc1 S21 dB Mag 10 dB / Ref 0 dB
Cal Smo Offs
1
• M 1 2.400000 GHz 17.518 dB
M 2 2.441000 GHz 17.378 dB
M 3 2.483500 GHz 17.270 dB
S21
30
M
M
23
M1
20
10
0
-10
-20
-30
-40
-50
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/22/2009,8:08 AM
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BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Reverse Isolation
10 MHz – 12 GHz Sweep
Trc1 S12 dB Mag 10 dB / Ref 0 dB
Cal Smo Offs
1
• M 1 2.400000 GHz -27.937 dB
M 2 2.441000 GHz -27.810 dB
M 3 2.483500 GHz -27.673 dB
S12
20
10
0
-10
-20
M
M
M1
23
-30
-40
-50
-60
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/22/2009,8:08 AM
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Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Reverse Isolation, AMPLIFIER DC POWER TURNED OFF.
10 MHz – 12 GHz Sweep
Trc1 S12 dB Mag 10 dB / Ref 0 dB
Cal Smo Offs
1
• M 1 2.441000 GHz -18.762 dB
S12
0
-10
M1
-20
-30
-40
-50
-60
-70
-80
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/22/2009,8:48 AM
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BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Output Return Loss, Log Mag
10 MHz to 12 GHz Sweep
Trc1 S22 dB Mag 5 dB / Ref 0 dB
Cal Smo Offs
1
• M 1 2.400000 GHz -9.7484 dB
M 2 2.441000 GHz -10.136 dB
M 3 2.483500 GHz -10.685 dB
S22
10
5
0
-5
M
M1
2
M3
-10
-15
-20
-25
-30
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/22/2009,8:09 AM
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Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
Output Return Loss, Smith Chart
Reference Plane = Output SMA Connector on PC Board
10 MHz to 12 GHz Sweep
Trc1 S22 Smith
Ref 1 U
Cal Smo Offs
1
1
S22
29.996
j17.992
1.193
2
M 2 2.441000 GHz 31.680
j18.833
1.228
M 3 2.483500 GHz 33.453
j19.068
5
1.222
• M 1 2.400000 GHz
0.5
MMM123
0
0.2
0.5
1
2
Ω
Ω
nH
Ω
Ω
nH
Ω
Ω
nH
5
-5
-0.5
-2
-1
Ch1
Start 10 MHz
Pwr -25 dBm
Stop 12 GHz
1/22/2009,8:10 AM
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Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
11
Amplifier Third Order Intercept (TOI) Measurement
In-Band Third Order Intercept (IIP3) Test.
Input Stimulus: f1=2440 MHz, f2=2441 MHz, -26 dBm each tone.
Input IP3 = -26+(45.7 / 2) = - 3.2 dBm. Output IP3 = - 3.2 dBm + 17.4 dB gain = +14.2 dBm.
Application Note
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BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
12
Amplifier Turn-On / Turn-Off Time Measurements
The amplifier is tested for turn-on / turn-off time. See diagram below. The RF signal generator runs
continuously at a power level sufficient to drive the output of the LNA to approximately 0 dBm when the
LNA has DC power ON.
Agilent DSO6104A
Digital Oscilloscope
+Vcc to amplifier
‘Scope
Probe
+DC Pin
Amplifier
3 dB
Attenuator
Pad
RF Signal
Generator
Agilent
8473B
Detector
Ch. 1 (Trigger, edge)
1 Megaohm input Z
Ch. 2 ( 1 Megaohm or
50 ohm input Z)
! Note !
It may be necessary to set Ch. 2 Input Impedance to 50 ohms instead
of 1M ohm. 1M ohm setting may not allow detector to discharge
rapidly, depending on detector type and detector’s output capacitance,
and might give erroneous results to turn-off time measurement, e.g.
could indicate excessively long turn-off times. The user can test turnoff time with Ch. 2 input impedance set to 1M ohm and then 50 ohms
and see if the two results differ.
1. Signal Generator set such that output power of Amplifier is ~ 0 dBm when LNA is
powered ON
2. Channel 1 of oscilloscope monitors input power supply voltage to Amplifier (+1.8,
+2.8 or +3.0 volts ON, depending on the amplifier, and 0 volts when OFF). Hook
oscilloscope probe to +Vcc pin on amplifier to monitor Vcc rising / falling edge.
3. Channel 2 of oscilloscope monitors rectified RF output of Amplifier
4. To make measurement of turn-on time, leave DC power supply on, disconnect and
“ground” +Vcc line to discharge amplifier, then insert Vcc line back into power supply.
This method will eliminate turn on time transient of power supply itself. Set up trigger of
O’Scope to trigger on rising edge of Ch.1
5. To make measurement of turn-off time, with supply ON, reset o’scope, setup trigger
to trigger on falling edge of Ch. 1, and simply remove +Vcc line / wire from the power
supply input to turn amplifier OFF.
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Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
a) Turn On Time:
Refer to oscilloscope screen-shot below. Upper trace (yellow, Channel 1) is the DC power supply turnon step waveform whereas the lower trace (green, Channel 2) is the rectified RF output signal of the
LNA stage. Amplifier turn-on time is aproximately 480 nanoseconds, or ~ 0.5 microseconds.
Main source of time delay in the LNA turn-on event are the R-C time constants formed by (R3 * C4),
[(R2+R3) * C2], etc. Charge storage has been minimized in this circuit so as to speed up turn on and
turn off times. (Refer to Schematic diagram on page 6). Note that the input impedance of the
oscilloscope for Channel 2, which senses the rectified RF output power of the amplifier, is set to 1M
ohm for this picture. Note both 50 ohm and 1M ohm input impedances where tested for turn-on time
and there was no appreciable differences in results for turn-on time measurement.
Application Note
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Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
b) Turn-Off Time:
Upper trace (Channel 1, yellow color) is the falling edge of the DC power supply voltage. Rectified RF
output signal (Channel 2, lower green trace) takes about ~ 32 nanoseconds, or 0.032
microseconds, to settle out after power supply is turned off.
Note that input impedance of digital oscilloscope which senses RF Detector Diode output
(Channel 2) is set to 50 ohms for this plot, as if a 1 M ohm input impedance were used, the
Schottky diode detector would have to discharge through the large 1M ohm impedance, which
would result in erroneously long turn-off times.
Application Note
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Rev. 1.1, 2009-01-23
Application Note No. 171
BFP740F 2.4 – 2.5 GHz LNA with < 1µSec Turn-On / Turn-Off Time
13
References
Note – the references below are embedded into this document and may be opened from within Adobe
Acrobat  by double-clicking on the respective paper clip icon.
[1]. BFP740F Datasheet, Infineon Technologies AG.
[2]. “A High IIP3 Low Noise Amplifier for 1900 MHz Applications Using the SiGe BFP620 Transistor”.
Applied Microwaves and Wireless, July 2000.
Pages 2 – 4 discusses the use of Inductive Emitter Degeneration and additional charge storage
(capacitance) to stabilize and linearize LNA’s using Silicon Bipolar RF Transistors. Unlike the LNA shown
in this reference, the LNA used in this Applications Note (AN171) had to minimize use of charge storage
in order to achieve fast ON / OFF times.
[3]. The embedded ZIP-format file below contains Gerber, Drill and Fabrication Drawing files for the
Printed Circuit Board shown in this Applications Note.
Application Note
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Rev. 1.1, 2009-01-23
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