This paper presents the design and simulation of a improved CMOS wideband 1-6Ghz low noise amplifier (LNA). The LNA can be suitable for several different kinds of standard receivers, including Global Position System, wireless local area network, Bluetooth and ZigBee. An active balun is added to the differential amplifier. The active balun can transform the signal received form the antenna or fitter into differential signal. The transformation reduces the number of matching network. The circuit of LNA is designed and then simulated with TSMC 0.18??m technology, and the simulation results illustrate that this proposed LNA achieves a good gain with suitable noise figure, input and output loss which gives a maximum gain of 14dB in the bandwidth with 4 dB noise figure.