This thesis describes the design of low noise amplifier (LNA) for the international Square Kilometre Array (SKA) project. LNAs in radio astronomy receivers play an important role of amplifying very weak signals from the Universe and the significance of the LNAs become more crucial in the SKA which is the largest and most sensitive radio telescope in the World. The aperture array (AA) system proposed for SKA is projected to deploy tens of millions of LNAs in a receiver system to survey large areas of the sky simultaneously over the frequency bands of 70-450MHz and 400-1400MHz. Hence LNA power efficiency has a significant implication in the SKA AA system due to the large number of the LNAs required. This thesis describes the design of 9 LNAs for the SKA. Seven LNAs with very low power consumption were designed, fabricated and characterised for SKA AA system using MIC technology by employing COTS components. Single ended and differential to single ended configurations were used for the lower frequency band of SKA AA system. Low noise figures (noise temperatures) of 0.6dB (43K) were achieved with high gain of more than 30dB at a power consumptions of less than 25mW for lower frequency band of AA. The LNAs designed to perform at 400-1400MHz have a very low power consumption of 28mW with an average noise figure (noise temperature) of 0.45dB (32K). Two MMIC LNAs based on low noise TQP13N pHEMT process of TriQuint Semiconductors with gate length of 130nm were designed for the low (0.7-1.8GHz) and high (8-10GHz) frequency ends of the SKA. The packaging and housing solutions of the SKA LNAs were implemented.The work described in this thesis shows low noise figures (noise temperatures) with high gains are achieved at a very low power consumption of less than 30mW for the MIC LNAs in the SKA AA system by using commercially available components.