AM Radio Amplifier with Filter Using the CPH3910 Application Note Overview This application note explains about ON Semiconductor’s CPH3910 which is used as a Low Noise Amplifier (LNA) for AM Radio. http://onsemi.com The CPH3910 is a silicon junction field effect transistor best suited for high-frequency applications which is assembled in the 3-pin surface mount package. For information about the performance, please refer to the datasheet of this product. The evaluation board is adjusted to provide +9.5dB gain in AM band (520 to 1720 kHz) and reduce gain to −80dB in FM band (76 to 108 MHz). A standard material FR4 is used for the printed circuit board (PCB). © Semiconductor Components Industries, LLC, 2014 October 2014- Rev. 0 1 Publication Order Number: ANDCPH3910_1/D AM Radio Amplifier with Filter Using the CPH3910 ■Summary of Data Ta = 25ºC, Input Power = -40 dBm, Zo = 50 Ω Parameter Symbol DC Voltage DC Current Result Unit Vdd 5.0 V Idd 26.5 mA Gp1 Condition f = 520 kHz 9.45 f = 1120 kHz 9.85 f = 1720 kHz 9.81 f = 76 MHz -89.9 f = 90 MHz -87.6 f = 108 MHz -82.3 f = 520 kHz -0.03 f = 1120 kHz -0.19 f = 1720 kHz -0.48 f = 520 kHz -0.81 f = 1120 kHz -1.08 f = 1720 kHz -1.67 f = 520 kHz -48.2 f = 1120 kHz -41.5 f = 1720 kHz -37.9 Power Gain dB Gp2 Input Return Loss Output Return Loss Isolation RLin RLout ISL http://www.onsemi.com 2 dB dB dB AM Radio Amplifier with Filter Using the CPH3910 ■Circuit Design Vdd = 5V L4 C2 INPUT C4 L1 L2 R2 R7 R4 L3 FET1 R1 C1 ■Evaluation Board http://www.onsemi.com 3 C5 OUTPUT R5 R3 R6 C7 C3 C6 AM Radio Amplifier with Filter Using the CPH3910 ■Bill of Materials Item Symbol Value Manufacture Size J-FET FET1 CPH3910 ON Semiconductor SC-59 C1 10 pF Murata GRM155 1005 C2 12 pF Murata GQM188 1608 C3 120 pF Murata GRM155 1005 C4,C5,C6,C7 0.1 uF ROHM MCH182CN 1608 R1 22 kΩ Various 1608 R2 270 Ω Various 1608 R3 100 kΩ Various 1608 R4 150 Ω Various 1608 R5 100 kΩ Various 1608 R6 4.7 Ω Various 1608 R7 120 kΩ Various 1608 L1,L2,L3 3.3 uH TDK NLV25T 2520 L4 330 uH TDK NLCV32T 3225 Capacitor Resistor Inductor Material FR-4 http://www.onsemi.com 4 25 x 13 mm AM Radio Amplifier with Filter Using the CPH3910 ■Measurement Results 16 0 14 ‐10 ‐20 Isolation ‐ dB Power Gain ‐ dB 12 10 8 6 ‐30 ‐40 ‐50 4 ‐60 2 0 ‐70 0.1 1 Frequency ‐ MH z 0.1 10 10 Figure 2 Isolation vs. Frequency 0 ‐1 ‐2 ‐2 Output Return Loss ‐ dB 0 ‐1 ‐3 ‐4 ‐5 ‐6 ‐7 ‐8 ‐9 ‐3 ‐4 ‐5 ‐6 ‐7 ‐8 ‐9 ‐10 ‐10 0.1 1 Frequency ‐ MHz 10 0.1 1 Frequency ‐ MHz Figure 4 Output Return Loss vs. Frequency S(4,4) Figure 3 Input Return Loss vs. Frequency S(3,3) Input Return Loss ‐ dB Figure 1 Power Gain vs. Frequency 1 Frequency ‐ MH z freq (520.0kHz 1.720MHz) 520 kHz to to1720 KHz freq (520.0kHz 1.720MHz) 520 kHz toto1720 kHz Figure 5 Smith Chart S11 Figure 6 Smith Chart S22 http://www.onsemi.com 5 10 AM Radio Amplifier with Filter Using the CPH3910 20 10 0 ‐10 ‐20 ‐30 ‐40 ‐50 ‐60 ‐70 ‐80 ‐90 ‐100 16 S21 S11 ↓ 14 ↑ S22 12 Power Gain ‐ dB S11,S21,S12,S22 ‐ dB ■Measurement Results S12 10 6V 7V ↓ ↑ 3V 8 6 4 2 0 0.1 1 10 Frequency ‐ MHz 100 1000 0.1 Figure 7 Wide Span 1 Frequency ‐ MHz Figure 8 Voltage Dependency http://www.onsemi.com 6 10 AM Radio Amplifier with Filter Using the CPH3910 ON Semiconductor and the ON logo are registered trademarks of Semiconductor Components Industries, LLC (SCILLC) or its subsidiaries in the United States and/or other countries. SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent-Marking.pdf . SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. 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