Application Notes

H
Philips Semiconductors B.V.
Gerstweg 2, 6534 AE Nijmegen, The Netherlands
Report nr.
Author
Date
Department
: RNR-T45-97-B-006
: T.F. Buss
: Jan. 6 1997
: P.G. Transistors & Diodes, Development
900MHz LOW NOISE AMPLIFIER
WITH THE BFG403W
Abstract:
This application note contains an example of a Low Noise Amplifier with the new BFG403W Double Poly
RF-transistor. The LNA is designed for a frequency f=900MHz, VSUP~1.5V, ISUP~1mA.
Measured performance at f=900MHz: Noise Figure NF~1.8dB, gain S21 ~16dB.
Appendix I: 900MHz LNA circuit
Appendix II: Printlayout and list of used components & materials
Appendix III: Measured Performance
1
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Philips Semiconductors B.V.
Introduction:
With the new Philips silicon bipolar double poly BFG400W series, it is possible to design low noise
amplifiers for high frequency 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 900MHz.
Because this LNA has an extreme low power-consumption, it is well suited for pager front-end
applications.
Designing the circuit:
The circuit is designed to show the following performance:
transistor: BFG403W
Vce~0.9V, Ic ~1mA, VSUP~1.5V
freq=900MHz
Gain~16dB
NF<=1.8dB
VSWRi<1:3
VSWRo<1:2
Designing the layout:
A lay-out has been designed with HP-MDS. Appendix II contains the printlayout.
Measurements:
Measurements of the total circuit are done (Appendix III).
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Philips Semiconductors B.V.
Appendix I: Schematic of the circuit
C3
C4
R1
+VSUP
C2
R3
R4
Coil_2
Coil_1
R2
OUT
50Ω
C5
IN
50Ω
C1
W1
BFG403W
µS4:
µS4
L1
L2
µS4
D1
L3
W2
Figure 1: LNA circuit
900MHz LNA Component list: 900MHz LNA Component list:
Component
Value
Purpose, comment
R1
Bias (coll.-base)
13
kΩ
R2
in series with coll. for better S22, stability and reducing gain.
150 Ω
R3
RF blocking
22
Ω
R4
Bias, series with coll., cancelling hFE spread
390 Ω
C1
1.2 pF
Input match (input to base)
C2
27
pF
900 MHz short (L1 to ground)
C3
27
pF
900 MHz short (L2 to ground)
C4
100 nF
RF decoupling collector bias
C5
1.2 pF
Output match (collector to output)
Coil_1
15
nH
Input match (base-bias)
Coil_2
15
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
L1
1.0mm
length µ-stripline; Z0~48Ω (PCB: εr ~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
C7
C5
C6
L1
R2
C2
C4
L2
R1
Vsup
R4
R3
C3
900MHz LOW NOISE AMP.
Figure 2: Printlayout
Comment: C6 and C7 are not used in this LNA.
900MHz LNA Component list:
Component:
PCB
R1
R2
R3
R4
C1
C2
C3
C4
C5
L1
L2
Value:
FR4: εr ~4.6
13
kΩ
150 Ω
22
Ω
390 Ω
1.2 pF
27
pF
27
pF
100 nF
1.2 pF
15
nH
15
nH
size:
H=0.5mm
0603 Philips
0603 Philips
0603 Philips
0603 Philips
0603 Philips
0603 Philips
0603 Philips
0805 Philips
0603 Philips
0805CS Coilcraft
0805CS Coilcraft
5
RFout
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Philips Semiconductors B.V.
Appendix III: Measured Performance
BFG403W; f=900MHz
2
VSUP [V] ISUP [mA]
|S 21| [dB]
Gain
|S 12| [dB]
Isolation
VSWRi
VSWRo
Noise Figure [dB]
1.1
1.5
1.7
-27
-30
-31
3.0
2.7
2.8
1.6
1.5
1.5
1.7
1.8
2.0
0.5
1.0
1.5
13
16
17
2
6
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