Cmos Variable Gain Low Noise Amplifier Design

During the last few decades, many of the developed countries have moved from analog terrestrial broadcasting to digital broadcasting, including the United States, the Republic of Korea, Western Europe, and Japan. Deployment of DTV (Digital TV) systems has also begun in South America, China and the rest of North America. Many countries have developed their own standards, and video reception with hand-held mobile devices has drawn more and more attention. A multi-standard, multi-band wideband receiver has been proved to be one of the most efficient candidates to enable the same service in different areas.In this thesis, a wideband variable gain low noise amplifier(VGLNA) in a DTV tuner is designed and discussed in great detail.First of all, requirements of the wideband VGLNA are given based on a variety of DTV broadcast standards and the given specification of a multi-standard multi-band tuner. Then, basic concepts and core ideas of LNAs are discussed in detail.Secondly, a wideband LNA based on an active feedback technique is presented in great detail, including the voltage gain, the input return loss, NF, IIP3and stability etc.Thirdly, the active feedback LNA serves as the core amplifier of VGLNA, where constant-Gm biasing technique is used. Resistive attenuator is added to compose a complete CMOS LNA with a specified range of gain control; meanwhile, a great attention is paid in the analysis and discussion of the gain range, gain step, NF and IIP3etc.Finally, the layout of the VGLNA is presented and simulated results are given. According to the post simulation results, the VGLNA has a voltage gain of22dB and20dB respectively in VHF(50-250MHz) and UHF(470-860MHz) bands. At the maximum gain, NF can be as low as1.16dB and1.41dB, IIP3is+0.5dBm and+1dBm, S11keeps lower than-10dB and-8dB, in VHF and UHF bands, respectively. The supply voltage is1.8V, and the current consumption is lower than8mA in both VHF and UHF bands.