DESIGN APPLICATION NOTE -- AN077 DESIGN APPLICATION NOTE --- AN077 SBB-2089 High CSO Push-Pull CATV Amplifier Abstract: With the abundance of data and voice traffic being transmitted across standard cable and wireless pathways and the ever increasing linearity requirements of CATV amplifiers, there is a great need for amplification that optimizes gain, VSWR, efficiency and linearity. This application note demonstrates the use of two SBB-2089 amplifiers in a pushpull configuration to achieve excellent CSO/CTB/XMOD performance from 50-860 MHz. Introduction: Inherent in push-pull amplifiers is the distinct cancellation of second order harmonics and intermodulation products. The low cost of RFMD amplifiers, coupled with their excellent linearity, makes them an easy choice for use in high linearity CATV applications. Table 1 contains a summary of performance of the SBB-2089 push-pull amplifier. Figures 2 and 3 illustrate the push-pull application circuit schematic and PCB layout. All measurements in this application note were taken in a 75 Ohm system. Symbol Parameter Freq.(MHz ) Min. Typ. Units 17.8 17.0 16.4 16.2 dB G Small Signal Gain 50 500 870 1000 IRL Input Return Loss 500 100-870 15.0 ORL Output Return Loss 500 100-870 16.0 C SO Worst Case Over Band, 79 Ch., Flat, +34dBmV 70 dB c CTB Worst Case Over Band, 79 Ch., Flat, +34dBmV 73 dB c XMOD Worst Case Over Band, 79 Ch., Flat, +34dBmV 67 dB c 24.0 16.0 dB dB Table 1: Typical RF Performance: VS=5V, ID=180mA @ TL=+25°C, Push-Pull Config. CTB/CSO/XMOD 34dBmV/Chan., 79 Chan., Flat 100 95 90 dBc 85 80 75 70 65 Xmod CTB CSO+ CSO- 60 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 Freq. (MHz) The information provided herein is believed to be reliable at press time.RFMD assumes no responsibility for inaccuracies or omissions.RFMD assumes no responsibility for the use of this information, and all such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any thirdparty. RFMD does not authorize or warrant anyRFMD product for use in life-support devices and/or systems. Copyright 2005 RFMD. All worldwide rights reserved. 303 S. Technology Ct., Broomfield, CO Phone: (800) SMI-MMIC 1 http://www.RFMD.com EAN-104613 Rev A DESIGN APPLICATION NOTE -- AN077 SBB-2089 High CSO Push-Pull CATV Amplifier Gain vs. Frequency 20 18 Gain (dB) 16 14 12 10 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 Frequency (MHz) Return Loss (dB) vs. Frequency 0 -5 Return Loss (dB) -10 -15 -20 -25 IRL -30 ORL -35 -40 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 Frequency (MHz) 303 S. Technology Ct., Broomfield, CO 80021 Phone: (800) SMI-MMIC 2 http://www.RFMD.com EAN-104613 Rev A DESIGN APPLICATION NOTE -- AN077 SBB-2089 High CSO Push-Pull CATV Amplifier Vs = +5 V 1200 pF 1 uF 1200 nH SBB2089 8200 pF Macom ETC1-1-13 Macom ETC1-1-13 SBB2089 1200 nH Vs = +5 V 1 uF 1200 pF S P 3 4 S S P 3 5 4 1 1 5 P Figure 2: SBB-2089 Push-Pull Schematic + S P Figure 3: SBB-2089 Push-Pull PCB Layout 303 S. Technology Ct., Broomfield, CO 80021 Phone: (800) SMI-MMIC 3 http://www.RFMD.com EAN-104613 Rev A