A variable gain low noise amplifier (VGLNA) using a 0.35 μm SiGe HBT process is described. A VGLNA with linear gain control and high linearity has been developed for 2.4 GHz ISM band applications. The gain control circuit is achieved without degrading either the input or the output VSWR. This technique can also simultaneously realize low noise figure and high linearity. The designed VGLNA achieved a gain of 19 dB, a noise figure of 2.7 dB, a third-order intercept point of -12 dBm, and a linear gain control range of 7.2 dB.
- Active balun