MBC13720

The MBC13720 SiGe:C LNA is designed for applications in the 400 MHz to 2.4 GHz range. It has four different modes; Low IP3, High IP3, Bypass, and Standby. The IC is programmable through the Enable 1 and 2 pins. In Low IP3 mode, the current consumption is optimized. Current consumption is higher in High IP3 mode to boost the intercept point performance. The gain difference between Low IP3 and High IP3 modes is typically 1.0 dB and typically the Low IP3 mode has a slightly better noise figure performance.

The internal bypass switch is designed for broadband applications. One of the advantages of the MBC13720 is the simplification of matching network in both bypass and amplifier modes. The bypass switch is designed such that the changes of input and output return losses between bypass mode and amplifier mode is minimized. As a result, the mismatch at the LNA input and output is minimized and therefore, the matching network design is simplified as well.

In the design of the external matching network, conjugate match condition does not necessarily provide the best noise figure performance. Balancing between noise figure, gain, and intercept point is the major design consideration. Typical circuits are provided in Figures 2 and 3 for 1.9 GHz, 2.4 GHz and 900 MHz applications.

In Figure 2, it shows the typical application circuit at 1.9 and 2.4 GHz. The noise figure, input intercept point, gain, and return losses are optimized. L2 and C2 act as a low frequency trap to improve the input intercept point. The noise figure measured on this board is 1.4 dB (in Low IP3 mode) at 1.9 GHz, including the external components, connectors, and PC board. The input third order intercept point is 10 dBm (in High IP3 mode).