Philips Semiconductors B.V. Gerstweg 2, 6534 AE Nijmegen, The Netherlands Report nr. Author Date Department : RNR-T45-97-B-0920 : T.F. Buss : 20-11-97 : P.G. Transistors & Diodes, Development 400MHz LOW NOISE AMPLIFIER WITH THE BFG540W/X Abstract: This application note contains an example of a Low Noise Amplifier with the BFG540W/X RF-transistor. The LNA is designed for a frequency f=400MHz, VSUP=3.0V, ISUP~7.5mA. Measured performance at f=400MHz: Noise Figure NF~1.0dB, rf-Gain S21 ~15.5dB, Input_IP3~2dBm Applications: LNA for a 400MHz CDMA system (Chinese market). Appendix I: 400MHz LNA circuit Appendix II: Printlayout and list of used components & materials Appendix III: Results of simulations and measurements 1 Philips Semiconductors B.V. Introduction: With Philips silicon wideband transistors, it is possible to design low noise amplifiers for UHF-applications with a low current and a low supply voltage. These amplifiers are well suited for the new generation low voltage high frequency wireless applications. In this note an example of such an amplifier will be given. This amplifier is designed for a working frequency of 400MHz. Designing the circuit: The circuit is designed to show the following performance (target): transistor: BFG540W/X V ce=2V, Ic<10mA, V SUP=3.0V. freq=400MHz Gain~15dB NF<1.5dB Input_IP3>+0dBm VSWRi<1:2 VSWRo<1:2 The in- and outputmatching is realised with a LC-combination. Also extra emitter-inductance on both emitterleads (µ-strips) are used to improve the matching and the Noise Figure. Designing the layout: A lay-out has been designed with HP-MDS. Appendix II contains the printlayout. Measurements: Simulations (with realistic RF-models of al used parts) and measurements of the total circuit (epoxy PCB) are done (Appendix III). 2 Philips Semiconductors B.V. Appendix I: Schematic of the circuit C4 C3 R1 R3 C5 +VSUP C2 Coil_2 Coil_1 R2 C6 OUT 50Ω C1 IN 50Ω C7 W1 BFG540W/X µS4: µS4 L1 µS4 L2 D1 L3 W2 Figure 1: LNA circuit 400MHz LNA Component list: 400MHz LNA Component list: Component Value Purpose, comment R1 22 kΩ Bias (coll.-base) R2 22 Ω in series with coll. for better S22, stability and reducing gain. R3 100 Ω Bias, series with coll., cancelling h FE spread C1 150 pF Input match (input to base) C2 150 pF 400MHz short (L1 to ground) C3 22 nF LF-short, improving IP3 performance C4 22 nF LF-short, improving IP3 performance C5 150 pF 400MHz short (L2 to ground) C6 8.2 pF Output match (collector to output) C7 4.7 pF Output match, stability (collector to emitter) Coil_1 22 nH Input match (base-bias) Coil_2 22 nH Output match (collector-bias) µs4 (see next µ-stripline Emitter-induction table) 3 Philips Semiconductors B.V. µS4 Emitter inductance of µ-stripline and via-hole (see on former page: Schematic of the circuit): Name Dimension Description 2.5mm L1 length µ-stripline; Z0~48Ω (PCB: ε r ~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 4 Philips Semiconductors B.V. Appendix II: Printlayout and list of used components & materials RFin C1 C6 C7 C2,C3 T L1 R2 R1 L2 Vsup R3 C4,C5 400MHz LOW NOISE AMP. Figure 2: Printlayout 400MHz LNA Component list: Component: PCB R1 R2 R3 C1 C2 C3 C4 C5 C6 C7 Coil_1 Coil_2 T Value: FR4: ε r ~4.6 22 kΩ 22 Ω 100 Ω 150 pF 150 pF 22 nF 22 nF 150 pF 8.2 pF 4.7 pF 22 nH 22 nH BFG540W/X size: H=0.5mm 0603 Philips 0603 Philips 0603 Philips 0603 Philips NPO 0603 Philips NPO 0603 Philips X7R 0603 Philips X7R 0805 Philips NPO 0603 Philips NPO 0603 Philips NPO 0805CS Coilcraft 0805CS Coilcraft SOT343 5 RFout Philips Semiconductors B.V. Appendix III: Results of simulations and measurements Conditions: V SUP=3.0V, ISUP=8mA, f=400MHz Simulation HP-MDS Measured Performance Comment: f=400MHz BFG540W/X SPICE model |S21|2 [dB] 15.5 15.6 note 1 |S12|2 [dB] -26.2 -28 note 1 VSWRi 1.7 1.8 note 1 VSWRo 1.6 2.0 note 1 Noise Figure [dB] 1.3 1.0 note 2 Input_IP3 [dBm] +6.7 +2 ∆f=1MHz, note 3 . note 1: Circuit is stable for all frequencies. note 2: The Noise Figure of the PCB is lower than the simulations (~0.3 dB). This difference is caused by the SPICE-model of the BFG540W/X, which is not optimised for noise. note 3: The Input_IP3 of the PCB is lower than the simulations (~4 dBm). This difference is caused by the SPICE-model of the BFG540W/X, which is not optimised for IP3. 6