Abstract: This application note explains how adding a degeneration inductor can improve the IP3 performance of the MAX2659 low-noise amplifier (LNA). The MAX2659 is a high-gain, low-noise amplifier (LNA) designed for use in GPS, Galileo, and GLONASS systems. The part is ideal for adding GPS functionality to both stand-alone personal navigation devices and mobile handsets, such as cell phones, smartphones, and PDAs. While the linearity of the MAX2659 is more than sufficient for most applications, it is possible to improve the device's IP3. This can be accomplished by adding a degeneration inductor between pin 2 (the amplifier's emitter) and ground, as shown in Figure 1. While this addition increases IP3 significantly, there is a trade off: the gain will reduce and the noise figure will degrade slightly. Figure 1. Typical application circuit for increased linearity. Using a 0.9nH inductor provides a good balance among linearity, gain, and noise figure. Measured results are shown in Table 1. Of course, a different value inductor can be used if more or less linearity is required, although gain and noise figure will change accordingly. Table 1. Performance of the MAX2659 With and Without a Degeneration Inductor Degeneration Inductor ICC (mA) Gain (dB) NF (dB) IP1dB (dBm) IIP3 (dBm)* 0.9nH 4.0 18.4 1.0 -7.0 6.2 None 4.1 20.5 0.8 -12 -0.5 *Tone 1 was at 1713.42MHz and -17dBm; Tone 2 was at 1851.42MHz and -59dBm. 関連製品   APP 4264: Sep 08, 2008 MAX2659 GPS/GNSS低ノイズアンプ フルデータシート (PDF, 128kB) 無料 サンプル 自動アップデート お客様が関心のある分野でアプリケーションノートが新規に掲載された際に自動通知Eメールの受信を希望する場合は、EE-Mail™にご登録ください。 We Want Your Feedback! フィードバックをお寄せください。 内容に満足されましたか、あるいは満足されていませんか？もっと良いページにできると思いますか？あるいは、単なるコメントでも結構です。フィードバックをお待ちしています。—マキシムはお客様からいただく訂正、提案を元に改善していきます。 このページを評価し、フィードバックを送信する。   ダウンロード、PDFフォーマット(25kB)  AN4264, AN 4264, APP4264, Appnote4264, Appnote 4264