This paper presents two ultra wide bandwidth low noise amplifiers utilizing 0.18-um AlGaN/GaN HEMT technology. The single-stage, resistive feedback microstrip amplifiers target two different frequency bands, 0.3 -4 GHz and 1.2 -18 GHz, capable of better than 13:1 bandwidth. Both amplifiers use dual-gate HEMT devices with an on-chip drain bias network. The low frequency amplifier achieves 17.7 dB flat gain between 300 MHz -3 GHz, and 1.2 dB minimum noise figure around 1.3 GHz. The high frequency LNA shows an average of 13 dB gain and between 2 to 3 dB noise figure across the band. The robust LNAs can be operated under various bias voltages while similar gain and noise figure performance are maintained.Index Terms -broadband amplifier, dual-gate HEMT, GaN HEMT, low noise amplifier, LNA.