400MHz Low Noise Amplifier with the BFG540W/X

Philips Semiconductors B.V.
Gerstweg 2, 6534 AE Nijmegen, The Netherlands
Report nr.
Author
Date
Department
: RNR-T45-97-B-0920
: T.F. Buss
: 20-11-97
: P.G. Transistors & Diodes, Development
400MHz LOW NOISE AMPLIFIER
WITH THE BFG540W/X
Abstract:
This application note contains an example of a Low Noise Amplifier with the BFG540W/X RF-transistor. The
LNA is designed for a frequency f=400MHz, VSUP=3.0V, ISUP~7.5mA.
Measured performance at f=400MHz: Noise Figure NF~1.0dB, rf-Gain S21 ~15.5dB,
Input_IP3~2dBm
Applications: LNA for a 400MHz CDMA system (Chinese market).
Appendix I: 400MHz LNA circuit
Appendix II: Printlayout and list of used components & materials
Appendix III: Results of simulations and measurements
1
Philips Semiconductors B.V.
Introduction:
With Philips silicon wideband transistors, it is possible to design low noise amplifiers for UHF-applications
with a low current and a low supply voltage. These amplifiers are well suited for the new generation low
voltage high frequency wireless applications. In this note an example of such an amplifier will be given. This
amplifier is designed for a working frequency of 400MHz.
Designing the circuit:
The circuit is designed to show the following performance (target):
transistor: BFG540W/X
V ce=2V, Ic<10mA, V SUP=3.0V.
freq=400MHz
Gain~15dB
NF<1.5dB
Input_IP3>+0dBm
VSWRi<1:2
VSWRo<1:2
The in- and outputmatching is realised with a LC-combination. Also extra emitter-inductance on both emitterleads (µ-strips) are used to improve the matching and the Noise Figure.
Designing the layout:
A lay-out has been designed with HP-MDS. Appendix II contains the printlayout.
Measurements:
Simulations (with realistic RF-models of al used parts) and measurements of the total circuit
(epoxy PCB) are done (Appendix III).
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Philips Semiconductors B.V.
Appendix I: Schematic of the circuit
C4
C3
R1
R3
C5
+VSUP
C2
Coil_2
Coil_1
R2
C6
OUT
50Ω
C1
IN
50Ω
C7
W1
BFG540W/X
µS4:
µS4
L1
µS4
L2
D1
L3
W2
Figure 1: LNA circuit
400MHz LNA Component list: 400MHz LNA Component list:
Component
Value
Purpose, comment
R1
22 kΩ
Bias (coll.-base)
R2
22 Ω
in series with coll. for better S22, stability and reducing gain.
R3
100 Ω
Bias, series with coll., cancelling h FE spread
C1
150 pF
Input match (input to base)
C2
150 pF
400MHz short (L1 to ground)
C3
22 nF
LF-short, improving IP3 performance
C4
22 nF
LF-short, improving IP3 performance
C5
150 pF
400MHz short (L2 to ground)
C6
8.2 pF
Output match (collector to output)
C7
4.7 pF
Output match, stability (collector to emitter)
Coil_1
22 nH
Input match (base-bias)
Coil_2
22 nH
Output match (collector-bias)
µs4
(see
next µ-stripline Emitter-induction
table)
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Philips Semiconductors B.V.
µS4 Emitter inductance of µ-stripline and via-hole (see on former page: Schematic of the circuit):
Name
Dimension Description
2.5mm
L1
length µ-stripline; Z0~48Ω (PCB: ε r ~4.6,
H=0.5mm)
L2
1.0mm
length interconnect stripline and via-hole area
L3
1.0mm
length via-hole area
W1
0.5mm
width µ-stripline
W2
1.0mm
width via-hole area
D1
0.4mm
diameter of via-hole
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Philips Semiconductors B.V.
Appendix II: Printlayout and list of used components & materials
RFin
C1
C6
C7
C2,C3
T
L1
R2
R1
L2
Vsup
R3
C4,C5
400MHz LOW NOISE AMP.
Figure 2: Printlayout
400MHz LNA Component list:
Component:
PCB
R1
R2
R3
C1
C2
C3
C4
C5
C6
C7
Coil_1
Coil_2
T
Value:
FR4: ε r ~4.6
22 kΩ
22 Ω
100 Ω
150 pF
150 pF
22 nF
22 nF
150 pF
8.2 pF
4.7 pF
22 nH
22 nH
BFG540W/X
size:
H=0.5mm
0603 Philips
0603 Philips
0603 Philips
0603 Philips NPO
0603 Philips NPO
0603 Philips X7R
0603 Philips X7R
0805 Philips NPO
0603 Philips NPO
0603 Philips NPO
0805CS Coilcraft
0805CS Coilcraft
SOT343
5
RFout
Philips Semiconductors B.V.
Appendix III: Results of simulations and measurements
Conditions: V SUP=3.0V, ISUP=8mA, f=400MHz
Simulation HP-MDS
Measured
Performance
Comment:
f=400MHz
BFG540W/X
SPICE model
|S21|2 [dB]
15.5
15.6
note 1
|S12|2 [dB]
-26.2
-28
note 1
VSWRi
1.7
1.8
note 1
VSWRo
1.6
2.0
note 1
Noise Figure [dB]
1.3
1.0
note 2
Input_IP3 [dBm]
+6.7
+2
∆f=1MHz, note 3
.
note 1: Circuit is stable for all frequencies.
note 2: The Noise Figure of the PCB is lower than the simulations (~0.3 dB). This difference is caused by the
SPICE-model of the BFG540W/X, which is not optimised for noise.
note 3: The Input_IP3 of the PCB is lower than the simulations (~4 dBm). This difference is caused by the
SPICE-model of the BFG540W/X, which is not optimised for IP3.
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