H Philips Semiconductors B.V. Report nr. Author Date Department : RNR-45-98-B-0703 : T.F. Buss / J.Bouwman : 28-10-1998 : Development DSC-N 900 MHz Driver with the BFG480W Abstract: This application note contains an example of a driver, designed for a frequency f=900MHz. At f=900 MHz: The output power Pout≅11dBm, the Noise Figure NF≅3.2dB, the Gain S21 ≥ 16dB and the OIP3≅25dBm. VSWRin ≤ 1:2.0, VSWRout ≤ 1:1.4 0. Introduction With the new Philips silicon bipolar double poly BFG400W 5th generation series, it is possible to design driver-amplifiers and PA’s for high frequency applications with a low supply voltage. These amplifiers are well suited for the new generation low voltage high frequency wireless applications. In this note an example with the BFG480W driver amplifier will be given. This amplifier is designed for a working frequency of 900 MHz. 1. 900 MHz Driver with the BFG480W Designing the circuit: The circuit is designed to show the following performance: transistor: BFG480W Vce~2V, Ic~60mA, VSUP=3.0V freq=900 MHz Gain~16dB VSWRi<1:2 VSWRo<1:2 OIP3>+20dBm The outputmatching is realised with a LC-combination. Also extra emitter-inductance on both emitterleads (µ-strips) is used to improve the matching. Figure 1 shows the Driver-circuit. C3 C4 +VSUP C5 R3 Coil_1 R1 C2 R2 IN 50Ω BFG480W OUT 50Ω W1 C1 µS1: µS1 L1 L2 µS1 D1 L3 W2 Figure 1: BFG480W Driver-circuit 2 Table 1 shows the components used for the BFG480W driver, table 2 shows the dimensions of the µstripline for the emitter-induction. Component Value Purpose, comment R1 2.2 kΩ Bias (coll.-base) R2 10 Ω Improve rf-stability R3 10 Ω DC-decoupling; cancelling hFE-spread C1 15 pF Input match (input to base) C2 15 pF Output match (collector to output) C3 27 pF 900MHz short (Coil_1 to ground) C4 100 nF Improving IP3 (by decoupling LF IP3 products) C5 1 nF RF decoupling collector bias (optional) Coil_1 120 nH Output match µs1 (see next table) µ-stripline Emitter-induction Table 1: 900 MHz BFG480W Driver component list: Name Dimension Description L1 1.5mm length µ-stripline; Z0~48Ω (PCB: εr ~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 Table 2: µS1 Emitter inductance of µ-stripline and via-hole (see on former page: Schematic of the circuit): 3 Designing the layout: A lay-out has been designed with HP-MDS. Figure 4 shows the printlayout. RFin C1 C2 C5 R1 P6 R2 L1 C3 Vsup C4 R3 BFG480W 900MHz PA PRINT LAYOUT Figure 2: BFG480W Driver-circuit layout Component: Value: size: P6 BFG480W SOT343R2 R1 2.2 kΩ 0603 Philips R2 10 Ω 0603 Philips R3 10 Ω 0603 Philips C1 15 pF 0603 Philips C2 15 pF 0603 Philips C3 27 pF 0603 Philips C4 100 nF 0805 Philips C5 1 nF 0603 Philips L1 120 nH 0805CS Coilcraft PCB εr~4.6, H=0.5mm FR4 Table 3: BFG480W 900 MHz Driver component list: note 1: The PCB of the Driver is adapted for this BFG480W application, therefore the shorts are used. 4 RFout Results of PCB measurements (1): BFG480W, f=900 MHz, VSUP = 3.0 V, ISUP ~ 50 mA @T = 25 oC Pin (dBm) Gp (dB) Pout (dBm) S11 (dB) S22 (dB) -30.00 -25.00 -20.00 -15.00 -10.00 -5.00 16.91 16.91 16.89 16.87 16.77 16.54 -13.09 -8.09 -3.11 1.87 6.77 11.54 -9.76 -9.74 -9.74 -9.92 -9.80 -9.60 -15.87 -15.87 -15.90 -15.82 -15.82 -15.84 -5.00 15.91 0.00 14.70 5.00 11.07 Table 4: Results measurements BFG480W 10.91 -9.10 14.70 -7.90 16.07 -5.60 900 MHz Driver amplifier - Comment: First part is measured with a Network Analyzer, second part (-5 to +5 dBm) with a Peak Power Analyzer. Results of PCB measurements (2): BFG480W, f=900 Mhz, VSUP=3.0V, ISUP~50mA @T=25oC Measurement Value Comment Noise Figure [dB] 3.2 IP3 [dBm] (input) 8.4 PIN=-20 dBm, ∆f=200 KHz IP3 [dBm] (output) 25.1 PIN=-20 dBm, ∆f=200 KHz Table 5: Results measurements BFG480W 900 MHz Driver amplifier 5 Figure 3 shows us the output power vs. input power -curve at 900 MHz. Measurements made with the Piek Power Analyzer (large signal) are displayed with the dashed line. Output power vs. input power 20.00 15.00 Pout (dBm) 10.00 5.00 0.00 -5.00 -10.00 -15.00 -30.00 -25.00 -20.00 -15.00 -10.00 Pin (dBm) -5.00 0.00 5.00 Pout (NWA) Pout (PPA) Figure 3: Output power vs. input power PPA=Piek Power Analyzer NWA=Network Analyzer 6