Sige Rfics Broadband Low Noise Amplifier

As critical component for receiver in wireless application, LNA(Low noise amplifier) has been applied in many fields such as mobile communication, radar, satellite, electronic counterwork, blueteeth technology and so on. The LNA must balance the specifications of noise figure, gain, band width, power consumption and impedance matching. SiGe HBTs can meet the above demand since they have excellent characteristics of high gain, low noise figure, wider and higher operation frequency and excellent linearity characteristic at low power consumption compared to Si BJTs.As its high performance, low cost and compatibility with Si technology, SiGe HBTs are emerging as replacements for the devices made by some expensive materials such as GaAs and InP.The characteristic of both device and circuit is vital to the SiGe HBT LNA. So the design of both SiGe HBT device and RF wide-band circuit is presented. Some main relative technologies are as follows:1,Germanium component is doped in the base of the device, and the current gain increases evidently as the energe of band gap in the base decreases. In order to improve the frequency property, The Germanium component increases linearly in the base from the emitter side to the collector side.2,In order to solve the problem of the outdiffusion of the base dopants, two solutions are put forward: 1) the SiGe:C base can solve the outdiffusion problem effectively. 2) the undoped buffer layer can also constrict the outdiffusion phenomenon. .otherwise, SiGe:C base can improve both frequency and gain performance of the SiGe HBT. 3,In order to keep smooth gain and wide bandwidth,the LNA circuit is designed with three stages,and two feed-back structures are adopted.4,A kind of on/off technology is used in the circuit to control the amplifier expediently also reduce power dissipation of the amplifier. The LNA will work only when needed.5,In order to have less RFIC area, all the stages of the circuit are self bias,and there is only one big inductance in the whole LNA circuit. Through the analysis and the design of SiGe HBT device and its circuit. a new type of amplifier with ON/OFF function is presented, which has low noise(<2.236dB) and smooth gain(>12dB) in its working frequency band of 0.5-6GHz. Simulation is finished successfully at present, and the amplifier satisfies the requirement.