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. 相关型号   APP 4264: Sep 08, 2008 MAX2659 GPS/GNSS低噪声放大器 完整的数据资料 (PDF, 128kB) 免费样品 自动更新 需要自动接收最新发布的应用笔记吗？请订阅EE-Mail™ (English only)。 我们期待您的反馈！ 喜欢？不喜欢？有待改善？或为我们提供建议？请与我们联系 — 我们将根据您的意见或建议改善我们的工作。 网页评价或提供建议   下载，PDF格式 (25kB)  AN4264, AN 4264, APP4264, Appnote4264, Appnote 4264