Philips Semiconductors B.V. Gerstweg 2, 6534 AE Nijmegen, The Netherlands Report nr. Author Date Department : RNR-T45-97-B-0688 : T. Buss : 26 Aug 1997 : P.G. Transistors & Diodes, Development 900MHz DRIVER-AMPLIFIER WITH ENABLE-SWITCH USING THE BFG425W Abstract: This application note contains an example of a Driver-Amplifier using the new BFG425W Double Poly RFtransistor. The driver can be switched on and off with a control-voltage VCON=0...3V. The driver is designed for a frequency f=900MHz. Performance at f=900MHz, T=250C: Power Gain >12dB. Appendix I: Schematic of the circuit Appendix II: Results of measurements Appendix III: Printlayout and list of used components & materials 1 Philips Semiconductors B.V. Introduction: With the new Philips silicon bipolar double poly BFG400W series, it is possible to design driver-amplifiers for high frequency 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 for 900MHz will be given. This driver can be switched on and off with a control-voltage VCON. Designing the circuit: The circuit is designed to show the following performance (target): transistor: BFG425W V SUP=3V, VCON=0V (driver disabled), ISUP~0mA V SUP=3V, VCON=3.0V (driver enabled), ISUP~11mA freq=900MHz Power Gain: >12dB VSWRi<1:2.5 VSWRo<1:2 The in- and outputmatching-circuits are realised with a RC-combination. No coils are used to reduce the price. The Enable is controlled at the base in order to reduce the control-current (V CON=3V : ICON~0.6mA). DCdecoupling in the emitter is used reduce the influence of HFE-spread. Designing the layout: A lay-out has been designed with HP-MDS. Appendix III contains the printlayout. Measurements: Measurements of the total circuit (epoxy PCB) are done (Appendix II). 2 Philips Semiconductors B.V. Appendix I: Schematic of the circuit C4 C3 +VCON +VSUP C5 R2 C6 OUT 50 C2 R1 C1 IN 50 BFG425W R3 R4 C7 Figure 1: Driver circuit 900MHz Driver Component list: Component: Value: Comment: R1 R2 R3 R4 C1 C2 C3 C4 C5 C6 C7 Bias, RF-block RF-block Bias. DC-decoupling Input match. Output match. 900MHz short. RF Decoupling 900MHz short. RF Decoupling 900MHz short. 2.7 k 100 3.9 k 56 150 pF 150 pF 27 pF 1 nF 27 pF 1 nF 27 pF 3 Philips Semiconductors B.V. Appendix II: Results measurements: BFG425W, V SUP=3.0V, ISUP~11.0mA@T=25 oC ,V CON=3.0V, ICON~0.6mA@T=25 oC Measurements PCB: Comment: f=900MHz |S 21|2 [dB] 15.5 P IN=-30dBm, T=25 oC GP [dB] 13 P IN=-10dBm, T=25 oC GP [dB] ~11 P IN=-10dBm, T -40 o C (Freeze spray) VSWRi VSWRo Noise Figure [dB] IP3 [dBm] (output) P IN=-30dBm, T=25 oC P IN=-30dBm, T=25 oC P IN=-30dBm, T=25 oC not measured 2.5 1.7 ~2.5 - Isup and S21 as function o 16 14 12 S21 10 8 Isup 6 4 2 0 0 0.5 1 1.5 2 2.5 3 Vcon [V Figure 2: ISUP and S21 as funcion of VCON. (VSUP=3.0V, f=900MHz) 4 3.5 Philips Semiconductors B.V. Appendix III: Printlayout and list of used components & materials RFin S4 C1 C7 RFout C2 R3 P5 C5, C6 R1 SHORT R4 Vcon R2 Vsup C3 S4 C4 900MHz Driver Amplifier with enable-switch BFG425W Figure 3: Printlayout 900MHz Driver Component list: Component: Value: size: R1 R2 R3 R4 C1 C2 C3 C4 C5 C6 C7 P5 PCB 2.7 k 100 3.9 k 56 150 pF 150 pF 27 pF 1 nF 27 pF 1 nF 27 pF BFG425W r ~4.6, H=0.5mm 0603 Philips 0603 Philips 0603 Philips 0603 Philips 0603 Philips 0603 Philips 0603 Philips 0603 Philips 0603 Philips 0603 Philips 0603 Philips SOT343R Philips FR4 note 1: The used PCB was designed for Low Noise Amplifier applications. Shorts and wires are used to adapt the PCB for this driver application. 5