AN11118
BFU725F/N1 1.5 GHz LNA evaluation board
Rev. 1.1 — 17 October 2011
Application note
Document information
Info
Content
Keywords
Abstract
LNA, 1.5 GHz, BFU725F, GPS
This document explains the BFU725F 1.5 GHz LNA evaluation board
NXP Semiconductors
AN11118
BFU725F/N1_1.5GHZ LNA EVB
Revision history
Rev
Date
1.1
1.0
20111017
20110921
Description
Modified BOM for better stability.
Initial document.
Contact information
For more information, please visit:
http://www.nxp.com
For sales office addresses, please send an email to:
salesaddresses@nxp.com
AN11118
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Application note
Rev. 1.1 — 17 October 2011
2 of 12
NXP Semiconductors
AN11118
BFU725F/N1_1.5GHZ LNA EVB
1. Introduction
The BFU725F/N1 is a wideband Silicon Germanium Amplifier transistor for high speed,
low noise applications. It is designed to be used for LNA applications up to 15 GHz like
GPS, Satellite radio, Cordless Phone, Wireless LAN and satellite LNB. The BFU725F/N1
comes in a SOT343F package that has 2-emitter pins to reduce emitter inductance (for
maximum gain).
The BFU725F/N1 is ideal in all kind of applications where cost matters. It also gives the
designer flexibility in his design work, like bias current, frequency of operation; optimize
for the parameter of interest e.g. noise; gain; IP3 etc
The 1.5GHz LNA evaluation board (EVB) is designed to evaluate the performance of the
BFU725F/N1 applied as a general ISM band LNA in the 1.5GHz range. In this document,
the application diagram, board layout, bill of material, and some typical results are given.
Fig 1 shows the evaluation board.
Fig 1.
AN11118
BFU725F/N1 1.5GHz LNA evaluation board
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Application note
Rev. 1.1 — 17 October 2011
3 of 12
NXP Semiconductors
AN11118
BFU725F/N1_1.5GHZ LNA EVB
2. General Description
The BFU725F/N1 is the first discrete HBT produced in NXPs SiGeC QuBIC4x BiCmos
process. SiGeC is a silicon germanium process with the addition of Carbon in the base
layer of the NPN transistor. The presence of carbon in the base layer suppresses the
boron diffusion during wafer processing that allows steeper and narrower SiGe HBT base
and a heavier doped base, this results in lower base resistance, hence lower noise and
higher cut off frequency (higher gain). In Table 1 a summary of the transistor
performance in terms of noise and gain is shown.
Table 1.
BFU725F/N1 figures
Measured at 2V Vce and 5mA Ic
Frequency [GHz]
Noise Figure [dB]
1.5
1.8
2.4
5.8
12
0.42
0.43
0.47
0.7
1.1
Associated gain [dB]
24
22
20
13.5
10
Table 2.
Pin
1
2
3
4
Pinning information of the BFU725F/N1
Description
Simplified outline
Emitter
Base
Emitter
Collector
Graphic symbol
3. Application Board
The BFU725F/N1 1.5GHz EVB simplifies the evaluation of the BFU725F/N1 wideband
transistor, for this frequency range. The EVB enables testing of the device performance
and requires no additional support circuitry. The board is fully assembled with
BFU725F/N1, including input- and output matching, to optimize the performance. For
input matching a compromise has to be made for optimum noise/maximum
gain/RL/usable bandwidth on the application and customer requirements. To prevent
unwanted oscillations the stability factor (K) must be greater than 1. The stability factor
can be increased at the cost of gain. The board is mounted with signal input and output
SMA connectors for connection to RF test equipment.
AN11118
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Application note
Rev. 1.1 — 17 October 2011
4 of 12
NXP Semiconductors
AN11118
BFU725F/N1_1.5GHZ LNA EVB
3.1 Application Circuit
In Fig 2 the application diagram as supplied on the evaluation board is given.
GND
V
CC
GND
X3
R3
R1
C4
R2
C5
C3
L3
Replaced by Resistor!
R4
L2
X2
RF in
X1
C1
BFU725F
L4
C2
RF out
Fig 2.
Circuit diagram of the evaluation board
3.2 Board Layout
Fig 3 shows the board layout with the components.
X1
C1
L2
C3
C4
R1
R2
L3
R3
Q1
L4
R4
C2
X3
1.5
X2
Fig 3.
AN11118
Printed Circuit Board of BFU725F/N1 1.5GHz Evaluation Board
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Application note
Rev. 1.1 — 17 October 2011
5 of 12
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