This paper presents a DC-11 GHz CMOS low noise amplifier (LNA) for software-defined radio (SDR). The broadband performance is extended to cover the spectrum from near DC to 11 GHz by adopting extra inductors with modified resistive feedback, folded current reuse topology. Bandwidth extension is proposed by inserting pole splitting, interstage and LC ladder inductors. A source follower jointly acts as the buffer stage for broadband output matching and feed-forward path for gain enhancement as well as noise cancellation. Simulation shows power gain of 11 +/- 4 dB and the NF ranging from 1.8 to 3 dB in 0.4-11 GHz band. The LNA achieves an average IIP3 of - 10 dBm while consumes only 5.3 mW. The proposed broadband LNA is designed in 0.18-mu m CMOS process from 1.5V supply.