900 MHz Driver with the BFG480W

H
Philips Semiconductors B.V.
Report nr.
Author
Date
Department
: RNR-45-98-B-0703
: T.F. Buss / J.Bouwman
: 28-10-1998
: Development DSC-N
900 MHz Driver
with the
BFG480W
Abstract:
This application note contains an example of a driver, designed for a frequency f=900MHz.
At f=900 MHz: The output power Pout≅11dBm, the Noise Figure NF≅3.2dB, the Gain S21 ≥ 16dB and
the OIP3≅25dBm. VSWRin ≤ 1:2.0, VSWRout ≤ 1:1.4
0. Introduction
With the new Philips silicon bipolar double poly BFG400W 5th generation series, it is possible to design
driver-amplifiers and PA’s for high frequency applications with a low supply voltage. These amplifiers are
well suited for the new generation low voltage high frequency wireless applications. In this note an
example with the BFG480W driver amplifier will be given. This amplifier is designed for a working
frequency of 900 MHz.
1. 900 MHz Driver with the BFG480W
Designing the circuit:
The circuit is designed to show the following performance:
transistor: BFG480W
Vce~2V, Ic~60mA, VSUP=3.0V
freq=900 MHz
Gain~16dB
VSWRi<1:2
VSWRo<1:2
OIP3>+20dBm
The outputmatching is realised with a LC-combination. Also extra emitter-inductance on both
emitterleads (µ-strips) is used to improve the matching.
Figure 1 shows the Driver-circuit.
C3
C4
+VSUP
C5
R3
Coil_1
R1
C2
R2
IN
50Ω
BFG480W
OUT
50Ω
W1
C1
µS1:
µS1
L1
L2
µS1
D1
L3
W2
Figure 1: BFG480W Driver-circuit
2
Table 1 shows the components used for the BFG480W driver, table 2 shows the dimensions of the µstripline for the emitter-induction.
Component
Value
Purpose, comment
R1
2.2 kΩ
Bias (coll.-base)
R2
10
Ω
Improve rf-stability
R3
10
Ω
DC-decoupling; cancelling hFE-spread
C1
15
pF
Input match (input to base)
C2
15
pF
Output match (collector to output)
C3
27
pF
900MHz short (Coil_1 to ground)
C4
100 nF
Improving IP3 (by decoupling LF IP3 products)
C5
1
nF
RF decoupling collector bias (optional)
Coil_1
120 nH
Output match
µs1
(see next table) µ-stripline Emitter-induction
Table 1: 900 MHz BFG480W Driver component list:
Name
Dimension Description
L1
1.5mm
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
Table 2: µS1 Emitter inductance of µ-stripline and via-hole
(see on former page: Schematic of the circuit):
3
Designing the layout:
A lay-out has been designed with HP-MDS. Figure 4 shows the printlayout.
RFin
C1
C2
C5
R1
P6
R2
L1
C3
Vsup
C4
R3
BFG480W 900MHz PA PRINT LAYOUT
Figure 2: BFG480W Driver-circuit layout
Component:
Value:
size:
P6
BFG480W
SOT343R2
R1
2.2 kΩ
0603 Philips
R2
10
Ω
0603 Philips
R3
10
Ω
0603 Philips
C1
15
pF
0603 Philips
C2
15
pF
0603 Philips
C3
27
pF
0603 Philips
C4
100 nF
0805 Philips
C5
1
nF
0603 Philips
L1
120 nH
0805CS Coilcraft
PCB
εr~4.6, H=0.5mm
FR4
Table 3: BFG480W 900 MHz Driver component list:
note 1:
The PCB of the Driver is adapted for this BFG480W application,
therefore the shorts are used.
4
RFout
Results of PCB measurements (1):
BFG480W, f=900 MHz, VSUP = 3.0 V, ISUP ~ 50 mA @T = 25 oC
Pin (dBm)
Gp (dB)
Pout (dBm)
S11 (dB)
S22 (dB)
-30.00
-25.00
-20.00
-15.00
-10.00
-5.00
16.91
16.91
16.89
16.87
16.77
16.54
-13.09
-8.09
-3.11
1.87
6.77
11.54
-9.76
-9.74
-9.74
-9.92
-9.80
-9.60
-15.87
-15.87
-15.90
-15.82
-15.82
-15.84
-5.00
15.91
0.00
14.70
5.00
11.07
Table 4: Results measurements BFG480W
10.91
-9.10
14.70
-7.90
16.07
-5.60
900 MHz Driver amplifier
-
Comment:
First part is measured with a Network Analyzer, second part (-5 to +5 dBm) with a Peak Power
Analyzer.
Results of PCB measurements (2):
BFG480W, f=900 Mhz, VSUP=3.0V, ISUP~50mA @T=25oC
Measurement
Value
Comment
Noise Figure [dB]
3.2
IP3 [dBm] (input)
8.4
PIN=-20 dBm, ∆f=200 KHz
IP3 [dBm] (output)
25.1
PIN=-20 dBm, ∆f=200 KHz
Table 5: Results measurements BFG480W 900 MHz Driver amplifier
5
Figure 3 shows us the output power vs. input power -curve at 900 MHz. Measurements made with the
Piek Power Analyzer (large signal) are displayed with the dashed line.
Output power vs. input power
20.00
15.00
Pout (dBm)
10.00
5.00
0.00
-5.00
-10.00
-15.00
-30.00
-25.00
-20.00
-15.00
-10.00
Pin (dBm)
-5.00
0.00
5.00
Pout (NWA)
Pout (PPA)
Figure 3: Output power vs. input power
PPA=Piek Power Analyzer
NWA=Network Analyzer
6
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