A pp l ic a t io n N o t e, R e v . 2. 0 , J a n. 2 00 7 A p p li c a t i o n N o t e N o . 0 7 5 H i g h T h i r d- O r d e r I n p u t I n te r c e p t P o i n t C D M A 8 0 0 Low Noise Amplifier R F & P r o t e c ti o n D e v i c e s 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. 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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 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 Application Note No. 075 High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier Features • Extremely high IIP3 of 10 dB at 850 MHz associated with a low current consumption • High overall performance at extraordinarily low cost 2 3 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 1.1 dB Input 3 order intercept point 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 Noise figure rd 1) 1) ∆f = 1 MHz, -25 dBm per tone Application Note 4 Rev. 2.0, 2007-01-08 Application Note No. 075 High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier Application Circuit Figure 1 shows the schematic of the application circuit. Input IP3 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 IP3 in about the same magnitude while output IP3 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 IP3 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 IP3. For more detailed information on increasing IP3 by low frequency grounding please refer to Infineon’s application note AN060 (BFP620) and AN057 (BFP540). Vcc R1 10Ω C1 100nF C3 100nF R2 33kΩ R3 2.2Ω L1 5.6nH L2 4.7nH C4 6.8pF RFin C2 10pF R4 0Ω RFout Q1 BFR380F 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, IP3 improvement C2 10 pF 0402 Various Input matching, DC block C3 100 pF 0603 Various RF decoupling, IP3 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 Application Note No. 075 High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier Table 2 Bill of Materials (cont’d) Name Value Package Manufacturer Function R3 2.2 Ω 0402 Various Stability R4 0Ω 0402 Various Jumper Vcc L2 Q1 NA C1 L1 NA 10 mm NA NA In R3 R2 C2 C3 R1 12 mm C4 R4 Out AN075_placement_on_PCB.vsd Figure 2 Component placement on PCB 0.2 mm FR4 35 µm Cu 35 µm Cu for mechanical rigidity of PCB 0.8 mm FR4 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 Application Note No. 075 High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier 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 Gain [dB] 15.5 15 14.5 14 13.5 13 0.83 0.84 0.85 0.86 0.87 Frequency [GHz] AN075_Gain(f).vsd Figure 4 Measured Gain 1.5 Noise Figure [dB] 1.4 1.3 1.2 1.1 1 0.9 0.8 0.83 0.84 0.85 Frequency [GHz] Figure 5 0.86 0.87 AN075_NF(f).vsd Measured Noise Figure Application Note 7 Rev. 2.0, 2007-01-08 Application Note No. 075 High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier 10 Return Loss [dB] 12 14 s11 16 s22 18 20 22 0.83 0.84 0.85 0.86 0.87 Frequency [GHz] AN075_Return_loss(f).vsd Figure 6 Measured In- and Output Return Loss Reverse Isolation [dB] 17 18 19 20 21 22 23 0.83 0.84 0.85 Frequeny [GHz] Figure 7 0.86 0.87 AN075_Reverse_isolation(f).vsd Measured Reverse Isolation Application Note 8 Rev. 2.0, 2007-01-08 Application Note No. 075 High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier 17 5 16 15 -5 Gain 14 -10 P out -15 Gain [dB] P out [dBm] 0 13 -20 12 -35 -30 -25 -20 -15 -10 -5 P in [dBm] AN075_Pout_Gain(Pin).vsd Figure 8 Measured Gain Compression 5 K, B1 4 3 2 K 1 B1 0 0 1 2 3 Frequency [GHz] Figure 9 4 5 6 A N075_K_B1(f).vsd Measured Stability Factor K and Stability Measured B1 Application Note 9 Rev. 2.0, 2007-01-08 Application Note No. 075 High Third-Order Input Intercept Point CDMA 800 Low Noise Amplifier 18 16 Gain [dB] 14 12 10 8 6 4 2 0 0 1 2 3 4 Frequency [GHz] Figure 10 5 6 AN075_GainWS(f).vsd Measured Gain - Wide Span 0 Return Loss [dB] 5 s11 10 15 s22 20 25 30 0 1 2 3 4 5 6 Frequency [GHz] AN075_Return_lossWS(f).vsd Figure 11 Measured Return Loss - Wide Span Application Note 10 Rev. 2.0, 2007-01-08