原标题：Avago MGA-231T6 GPS低噪音(LNA)放大方案

　　Avago 公司的MGA-231T6 是(0.9-3.5)GHz GPS//ISM/WIMAX低噪音放大器(LNA),采用GaAs 增强模式pHEMT工艺,具有高增益.低噪音和高线性特性,工作定压可低至1.8V,主要用作GPS, WLAN 和WIMAX低噪音放大器.本文介绍了MGA-231T6主要特性, 演示板,应用电路和所用元件表以及S参数测量参考平面.

　　Avago Technologies’ MGA-231T6 is a low-noise amplifier (LNA) designed for GPS/ISM/Wimax applications in the (0.9-3.5)GHz frequency range. The LNA uses Avago Tech­nologies’ proprietary GaAs Enhancement-mode pHEMT process to achieve high gain with very low noise figure and high linearity. Noise figure distribution is very tightly controlled. A CMOS-compatible shutdown pin is included either for turning the LNA on/off or for current adjust­ment.

　　The low noise figure and high gain, coupled with low cur­rent consumption make it suitable for use in critical low-power GPS applications or during low-battery situations.

　　MGA-231T6主要特性:

　　• Very Low Noise Figure

　　• High Gain and Linearity

　　• Low External Component Count

　　• Low Shutdown Current

　　• CMOS compatible shutdown pin (SD) current @ Vsd= 1.8V : 0.11mA

　　• Useable down to 1.8V supply

　　• Adjustable current via single external resistor/voltage

　　• Small package dimension: 2.0(L)x1.3(W)x0.4(H) mm Specifications (Typical performance @ 25°C) At 1.575GHz

　　• Vdd = 2.85V, Vsd = 1.8V, Idd =4mA

　　– Gain = 17.1 dB

　　– NF = 1.06 dB

　　– Input IP3 = 0.2 dBm

　　– Input P1dB = 7.7 dBm

　　MGA-231T6应用:

　　• LNA for GPS, WLAN and WIMAX

　　图1.MGA-231T6演示板和应用电路元件表

　　Notes:

　　1. Pin 4 must be left unconnected

　　2. L3 and L4 form the input matching network. C2 and L2 form a matching network at the output of the LNA.

　　3. L1 and R1 isolates the demoboard from external disturbances during measurement. It is not needed in actual application. Likewise, C1 and C3 mitigate the effect of external noise pickup on the Vdd and SD lines respectively. These components are not required in actual operation.

　　4. Bias control is achieved by either varying the SD voltage with/without R2, or fixing the SD voltage to Vdd and adjusting R2 for the desired current. R2 = 8.2 kOhm will result in 4mA when Vdd = 2.85V, Vsd = 1.8V or Vdd = 1.8V, Vsd = 2.6V. R2 = 5.6 kOhm will result in 6mA when Vdd = Vsd = 2.7V.

　　图2.MGA-231T6演示板和应用电路图

　　图3.MGA-231T6 S参数测量参考平面