AN RFMD® APPLICATION NOTE SGA-8343 GPS Application Circuits RFMD Worldwide Applications Design Application Note -- AN-061 Abstract RFMD’s SGA-8343 is a high performance SiGe amplifier designed for operation from DC to 6GHz. This application note illustrates application circuits for GPS (Global Positioning System) frequency band (1575MHz). The first application circuit is optimized for noise performance; the second one is optimized for input return loss. Introduction The application circuits were designed to achieve the optimum combination of NF, input return loss, and stability. All recommended components are standard values available from well-known manufacturers. Components specified in the bill of materials (BOM) have known parasitics which in some cases are critical to the circuit’s performance. Deviating from the recommended BOM may result in a performance shift due to varying parasitics. Matching component placement is critical to each circuit’s performance. Circuit Details SMDI will provide the detailed layout (AutoCAD format) to users wishing to use the exact same layout and PCB material shown in the following circuits. The circuits recommended within this application note were designed using the following PCB stack up: Material: GETEKTM ML 200C Core thickness: 0.031” Copper cladding: 1 oz. both sides Dielectric constant: 4.1 Dielectric loss tangent: 0.0089 (at 1GHz) Customers not wishing to use the exact material and layouts shown in this application note can design their own PCB using the critical transmission line impedances and phase lengths shown in the BOMs and layouts. NOTE: Many of our sample evaluation boards may come with an additional substrate and copper layer for mechanical stability. It has been assumed that the backside layer has no effect on the RF performance or circuit design. RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc. 091113 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 1 of 7 SGA-8343 GPS Application Circuits Design Considerations and Trade-Offs - Biasing Techniques All HBT amplifiers are subject to device current variation due to the decreasing nature of the internal VBE with increasing temperature. In the absence of an active bias circuit or resistive feedback, the decreasing VBE will result in increased base and collector currents. As the collector current continues to increase under constant VCE conditions, the device may eventually exceed its maximum dissipated power limit resulting in permanent device damage. The designs included in this application note contain passive bias circuits that stabilize the device current over temperature and desensitize the circuit to device process variation. The passive bias circuits used in these designs include a dropping resistor in the collector bias line and a voltage divider from the collector-to-base. Using this scheme, the amplifier can be biased from a single supply voltage. The collector dropping resistor is sized to drop >20% VCE, depending on the desired VCE. The voltage divider from collector-to-base, in conjunction with the dropping resistor, will stabilize the device current over temperature. The effectiveness increases with increasing voltage drop in collector bias line. Configuring the voltage divider such that the shunt current is 5-10 times larger than the desired base current desensitizes the circuit to beta variation. These two feedback mechanisms are sufficient to insure consistent performance over temperature and device process variations. Note that the voltage drop is clearly dependent on the nominal collector current and can be adjusted to generate the desired VCE from a fixed supply rail. The user should test the circuit over the operational extremes to guarantee adequate performance. An active bias circuit can be implemented if the user does not wish to sacrifice the voltage required by the aforementioned passive circuit. There are various active bias schemes suitable for HBTs. The user should choose an active bias circuit that best meets his/her cost, complexity, and performance requirements. Other Application Circuits Available (see AN-044) 1. 2. 3. 800MHz to 1000MHz, single-ended with series feedback, optimized for NF and S11<-10dB. 1800MHz to 2000MHz, single ended, optimized for NF and S11<-8dB. 2400MHz to 2500MHz, single-ended, optimized for NF and S11<-10dB. Vcc + V DROP Ic IB + V CE I SHUNT - Figure 1. Passive Bias Circuit Topology 091113 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 2 of 7 SGA-8343 GPS Application Circuits Vs R4 6 Q1a 2 1 C4 R3 R2 R1 R5 5 3 R6 4 Q1b C3 C5 C6 L2 L1 SGA-8343 Figure 2. Active Bias Circuit Topology SGA-8343(Z)-EVB4 1575MHz Application Schematic 091113 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 3 of 7 SGA-8343 GPS Application Circuits SGA-8343(Z)-EVB4 1575MHz Evaluation Board 091113 Ref. Des Part Number C1, 5, 7 ROHM MCH185A150J Value 15pF C2 ROHM MCH185A1R2C 1.2pF C3, 4, 6 Samsung CL 10B104KONC 0.1uF L1 TOKO LL 1608-FS39NJ 39nH L2 TOKO LL 1608-FS1N8S 1.8nH L3 TOKO LL 1608-FS3N9S 3.9nH R1, 3 ROHM MCR03J222 2.2K R2 ROHM MCR03J102 1.0K R4 ROHM MCR03J620 62 R5 ROHM MCR03J100 10 Z1 non-critical 50 Z2 6.5 degrees at 1575MHz 50 Z3 7.8 degrees at 1575MHz 50 Z4 6.4 degrees at 1575MHz 50 Z5 6.4 degrees at 1575MHz 50 Z6 non-critical 50 Z7 11.1 degrees at 1575MHz 50 Z8 6.3 degrees at 1575MHz 50 Z9 26.0 degrees at 1575MHz 60 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 4 of 7 SGA-8343 GPS Application Circuits Typical Performance: Optimal S11 Application Circuit (V S =3.3V, I CQ =10mA, 25C) Gain vs. Frequency NF vs. Frequency 2 18 1.8 16 1.6 dB dB 20 14 1.4 12 1.2 1 10 1.5 1.52 1.54 1.56 1.58 1.5 1.6 1.52 1.54 1.56 P1dB vs. Frequency 1.6 1.58 1.6 OIP3 vs. Frequency 30 10 8 28 6 26 dBm dBm 1.58 GHz GHz 4 2 24 22 0 1.5 1.52 1.54 1.56 1.58 20 1.6 1.5 1.52 1.54 GHz S11 vs. Frequency 1.56 GHz S22 vs. Frequency 0 0 -5 -5 dB dB -10 -10 -15 -15 -20 -20 -25 1 1.2 1.4 1.6 1.8 1 2 1.2 1.4 091113 1.6 1.8 2 GHz GHz Freq (GHz) P1dB (dBm) OIP3 (dBm) Gain (dB) S11 (dB) S22 (dB) 1.550 6.2 26.5 17.4 -17 -13 1.6 1.575 6.5 27.0 17.3 -20 -12 1.6 1.600 6.6 27.8 17.1 -21 -12 1.6 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. NF (dB) 5 of 7 SGA-8343 GPS Application Circuits Optimal S11 Appl ication Circuit (V S =3.3V, V CE =2.7V, I CQ =10mA) GND Vs=+3.3V (10mA) 62 2.2K 1K 0.1uF 10 1.3K 0.1uF 15pF 39nH 0.1uF 15pF 3.9nH 1.8nH 2.2pF 15pF ECB-101766-B SOT-343 - FB Ref. Des. Part Number Value Ref. Des. Part Number Value C1, 5, 7 ROHM MCH185A150J 15 pF Z1 C2 ROHM MCH185A2R2C 2.2 pF Z2 4.6 degrees @ 1575 MHz 50 Z3 3.9 degrees @ 1575 MHz 50 C3, 4, 6 Samsung CL10B104KONC 0.1uF non-critical 50 L1 TOKO LL1608-FS39NJ 39 nH Z4 7.1 degrees @ 1575 MHz 50 L2 TOKO LL1608-FS1N8S 1.8 nH Z5 6.4 degrees @ 1575 MHz 50 L3 TOKO LL1608-FS3N9S 3.9 nH Z6 6.4 degrees @ 1575 MHz 50 R1 ROHM MCR03J132 1.3K Z7 R2 ROHM MCR03J102 1.0K Z8 R3 ROHM MCR03J222 2.2K Z9 6.3 degrees @ 1575 MHz 50 R4 ROHM MCR03J620 62 Z10 26.0 degrees @ 1575 MHz 60 R5 ROHM MCR03J100 10 non-critical 3.2 degrees @ 1575 MHz 50 50 Optimal S11 Schematic R4 R3 Vs=3.3V C4 R2 R5 C5 Z10 C3 L2 C1 Z1 Z2 Z3 R1 L3 C6 C7 L1 Z4 Z5 SGA-8343 Z6 Z7 C2 pin 4 - Pad edge to via center pin 2 - Pad edge to grounding strip Z9 Z8 091113 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 6 of 7 SGA-8343 GPS Application Circuits Typical Performance: Optimal NF Application Circuit (V S =3.3V, I CQ =10mA, 25C) Gain vs. Frequency NF vs. Frequency 2 18 1.8 16 1.6 dB dBm 20 14 12 1.4 1.2 10 1 1.5 1.52 1.54 1.56 1.58 1.6 1.5 1.52 1.54 GHz P1dB vs. Frequency 1.58 1.6 1.58 1.6 OIP3 vs. Frequency 30 8 28 6 26 dBm 10 dBm 1.56 GHz 4 2 24 22 0 20 1.5 1.52 1.54 1.56 1.58 1.6 1.5 1.52 1.54 1.56 GHz GHz S22 vs. Frequency S11 vs. Frequency 0 0 -5 -10 dB dB -5 -10 -15 -20 -15 -25 -30 -20 1 1.2 1.4 1.6 1.8 1 2 1.2 1.4 1.8 2 GHz GHz 091113 1.6 Freq (GHz) P1dB (dBm) OIP3 (dBm) 1.550 6.7 26.3 Gain (dB) 15.8 S11 (dB) -10 S22 (dB) -26 1.22 1.575 6.8 26.5 15.7 -11 -28 1.22 1.600 6.8 26.8 15.6 -11 -29 1.25 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. NF (dB) 7 of 7