NXP Semiconductors AN10714, Application Note

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NXP Semiconductors
AN10714
Using the BLF574 in the 88 MHz to 108 MHz FM band
© NXP B.V. 2010. All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: salesaddresses@nxp.com
Date of release: 26 January 2010
Document identifier: AN10714_1
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
12. Figures
Fig 1. BLF574 input circuit schematic;
88 MHz to 108 MHz . . . . . . . . . . . . . . . . . . . . . . . .4
Fig 2. BLF574 output circuit schematic;
88 MHz to 108 MHz . . . . . . . . . . . . . . . . . . . . . . . .5
Fig 3. BLF574 PCB layout . . . . . . . . . . . . . . . . . . . . . . . .6
Fig 4. Cable length definition . . . . . . . . . . . . . . . . . . . . . .8
Fig 5. Photograph of the BLF574 circuit board . . . . . . . .9
Fig 6. Typical CW data; 88 MHz to 108 MHz . . . . . . . . . 11
Fig 7. Output gain and efficiency variation under
different drain voltage conditions . . . . . . . . . . . . .12
Fig 8. Output gain and efficiency comparison for
Class-B and Class-AB amplifiers . . . . . . . . . . . . 12
Fig 9. Second order harmonics as a function of
output power against frequency . . . . . . . . . . . . . 13
Fig 10. Device impedance convention . . . . . . . . . . . . . . 14
Fig 11. Input base plate drawing . . . . . . . . . . . . . . . . . . . 15
Fig 12. Device insert drawing . . . . . . . . . . . . . . . . . . . . . 16
Fig 13. Output base plate drawing . . . . . . . . . . . . . . . . . 17
Fig 14. BLF574 time-to-failure. . . . . . . . . . . . . . . . . . . . . 18
Fig 15. BLF574 test configuration . . . . . . . . . . . . . . . . . . 19
13. Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Circuit diagrams and PCB layout . . . . . . . . . . . 4
2.1 Circuit diagrams . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 BLF574 PCB layout . . . . . . . . . . . . . . . . . . . . . 6
2.3 Bill Of Materials . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 PCB form factor . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Amplifier design. . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1 Mounting considerations. . . . . . . . . . . . . . . . . . 9
3.2 Bias circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3 Amplifier alignment . . . . . . . . . . . . . . . . . . . . . 10
4 RF performance characteristics . . . . . . . . . . . 11
4.1 Continuous wave . . . . . . . . . . . . . . . . . . . . . . 11
4.2 Continuous wave graphics . . . . . . . . . . . . . . . 11
5 Input and output impedance. . . . . . . . . . . . . . 14
6 Base plate drawings . . . . . . . . . . . . . . . . . . . . 15
6.1 Input base plate . . . . . . . . . . . . . . . . . . . . . . . 15
6.2 Device insert . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.3 Output base plate . . . . . . . . . . . . . . . . . . . . . . 17
7 Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1 Calculating TTF . . . . . . . . . . . . . . . . . . . . . . . 17
8 Test configuration block diagram . . . . . . . . . 19
9 PCB layout diagrams. . . . . . . . . . . . . . . . . . . . 19
10 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . 19
11 Legal information. . . . . . . . . . . . . . . . . . . . . . . 20
11.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
11.2 Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
11.3 Trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
12 Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
13 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21