Application Note, Rev. 2.0, Jan. 2007 Application Note No. 075 High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier RF & Protection Devices
Edition 2007-01-08 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 be expected to cause the failure of that life-support device or system, or to affect the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body, or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered.
Application Note No. 075 Revision History: 2007-01-08, Rev. 2.0 Previous Version: 2002-08-05 Page Subjects (major changes since last revision) All Document layout change Application Note 3 Rev. 2.0, 2007-01-08
Features Extremely high IIP 3 of 10 db at 850 MHz associated with a low current consumption High overall performance at extraordinarily low cost 3 2 1 Introduction The BFR380F is a silicon bipolar transistor housed in a small outline TSFP-3 package. The BFR380F is a member of Infineon s new 3+ generation transistor family consisting of three different sizes of transistors: BFR340F, BFR360F and BFR380F. These transistors are 14 GHz transition-frequency devices which take advantage of the latest manufacturing techniques requiring fewer processing steps than other devices in their class, thereby offering excellent performance and device-to-device consistency at extraordinarily low cost. All types of 3+ transistors are also available in Infineon s new TSLP-3 package. The world s smallest chip size leadless plastic package for discrete components like diodes and transistors. With a noise figure of 1.1 db at 1800 MHz and a bias point of 3 V / 8 ma, the BFR380F is a good solution for costsensitive LNA designs. In addition, the BFR380F is an ideal choice for VCO applications due to its low flicker noise corner frequency of 15 khz. This application note describes the BFR380F as a CDMA 800 LNA for the frequency range between 830 MHz and 870 MHz. Table 1 shows the measured performance of the application circuit. All parameters include losses of PCB and SMA connectors. Table 1 Measured Performance at 850 MHz Parameter Value Unit Supply voltage 3 V Supply current 8.2 ma Gain 14.8 db Noise figure 1.1 db Input 3 rd order intercept point 1) 10.5 dbm Input return loss 14.4 db Output return loss 18.1 db Reverse isolation 20.2 db Input compression point -9 db 1) f = 1 MHz, -25 dbm per tone Application Note 4 Rev. 2.0, 2007-01-08
Application Circuit Figure 1 shows the schematic of the application circuit. Input IP 3 is improved by different measures. The first one is inductive emitter degeneration where a microstrip line between emitter and ground enlarges the emitter inductance. This additional emitter feedback decreases gain and increases input IP 3 in about the same magnitude while output IP 3 remains at the same level. As a drawback increased emitter inductance destabilizes the device at higher frequencies so a careful look at the circuit s stability factor is necessary when applying emitter degeneration. Another possibility to increase IP 3 on the whole is to provide low frequency paths to ground at base and collector to avoid AM modulation effects. At the base L1 and C1 form such a path at the transistor s base, the one at the collector consists of L2-R3-C3. In general the low frequency path at the base is the more efficient way to increase IP 3. For more detailed information on increasing IP 3 by low frequency grounding please refer to Infineon s application note AN060 (BFP620) and AN057 (BFP540). Vcc C1 100nF R2 33kΩ R1 10Ω C3 100nF R3 2.2Ω RFin C2 10pF L1 5.6nH L2 4.7nH Q1 BFR380F C4 6.8pF R4 0Ω RFout Inductive Emitter Degeneration (Microstrip): L = 1 mm, W = 0.2 mm AN075_schematic_diagram.vsd Figure 1 Schematic Diagram Table 2 Bill of Materials Name Value Package Manufacturer Function C1 100 nf 0603 Various RF decoupling, IP 3 improvement C2 10 pf 0402 Various Input matching, DC block C3 100 pf 0603 Various RF decoupling, IP 3 improvement C4 6.8 pf 0402 Various Output matching, DC block L1 5.6 nh 0402 Toko LL 1005-FH RF Choke, input matching L2 4.7 nh 0402 Toko LL 1005-FH RF Choke, output matching Q1 BFR380F TSFP-3 Infineon Si BJT R1 10 Ω 0402 Various Biasing R2 33 Ω 0402 Various Biasing Application Note 5 Rev. 2.0, 2007-01-08
Table 2 Bill of Materials (cont d) Name Value Package Manufacturer Function R3 2.2 Ω 0402 Various Stability R4 0 Ω 0402 Various Jumper 12 mm Vcc 10 mm R1 C2 NA R2 NA R3 C3 In NA C1 L1 Q1 NA L2 C4 R4 Out AN075_placement_on_PCB.vsd Figure 2 Component placement on PCB 0.2 mm FR4 35 µm Cu 35 µm Cu 0.8 mm FR4 for mechanical rigidity of PCB 35 µm Cu AN075_PCB_cross_section.vsd Figure 3 PCB Cross Section Evaluation boards for the LNA depicted in this application note are available from Infineon Technologies. Application Note 6 Rev. 2.0, 2007-01-08
Measured Curves The following pages show measurement graphs of the BFR380F LNA described in this application note. As mentioned before all measurement results presented here include losses of PCB and connectors, in other words. the reference plane is at the SMA connectors. 16 15.5 Gain [db] 15 14.5 14 13.5 13 0.83 0.84 0.85 0.86 0.87 AN075_Gain(f).vsd Figure 4 Measured Gain 1.5 1.4 Noise Figure [db] 1.3 1.2 1.1 1 0.9 0.8 0.83 0.84 0.85 0.86 0.87 AN075_NF(f).vsd Figure 5 Measured Noise Figure Application Note 7 Rev. 2.0, 2007-01-08
10 Return Loss [db] 12 14 16 18 20 s11 s22 22 0.83 0.84 0.85 0.86 0.87 AN075_Return_loss(f).vsd Figure 6 Measured In- and Output Return Loss 17 Reverse Isolation [db] 18 19 20 21 22 23 0.83 0.84 0.85 0.86 0.87 Frequeny [GHz] AN075_Reverse_isolation(f).vsd Figure 7 Measured Reverse Isolation Application Note 8 Rev. 2.0, 2007-01-08
17 5 16 0 P out [dbm] -5-10 Gain 15 14 Gain [db] -15 P out 13-20 -35-30 -25-20 -15-10 -5 12 P in [dbm] AN075_Pout_Gain(Pin).vsd Figure 8 Measured Gain Compression 5 4 K, B1 3 2 1 0 K B1 0 1 2 3 4 5 6 AN075_K_B1(f).vsd Figure 9 Measured Stability Factor K and Stability Measured B1 Application Note 9 Rev. 2.0, 2007-01-08
Gain [db] 18 16 14 12 10 8 6 4 2 0 0 1 2 3 4 5 6 AN075_GainWS(f).vsd Figure 10 Measured Gain - Wide Span 0 Return Loss [db] 5 10 15 20 25 s11 s22 30 0 1 2 3 4 5 6 AN075_Return_lossWS(f).vsd Figure 11 Measured Return Loss - Wide Span Application Note 10 Rev. 2.0, 2007-01-08