Design of power amplifier using silicon-germanium HBT

Recent efforts in the design of integrated circuits for RF communication transceiver have focused on achieving higher levels of integration by including more and more analog function blocks onto a single Silicon Chip. One of the final blocks that is yet to be successfully integrated is the power amplifier (PA). The PA is final functional block in the transmit path; its function is to amplify the signal to be transmitted to the required transmit power level. In general, PA's are difficult to integrate in SiGe because of the technology limitations that severely limit the efficiency of the PA.; This thesis describes the theoretical analysis and circuit techniques for the design and implementation of RF PA driver in SiGe technologies. To date, very few methods exist for designing a fully integrated PA; in the past, much of the design process has been empirical. The theoretical work in this thesis attempts to describe a method for designing a PA in SiGe without resorting to routine use of a circuit simulator. Using the collector current waveform of a SiGe PA (which is dependent both on the input and the output voltage waveforms) is determined to first order in order to generate an approximate solution to the design goal before a circuit analysis tool is required. Circuit techniques used to combat the technology limitations imposed by SiGe technologies include the use of the differential circuits in the signal path, a cascaded stage and a modified tuning method which allowed for the use of large output devices but not requiring passive devices that were not feasible in the SiGe technology.; A 1.7GHz to 2.4GHz, 25dBm SiGe PA was designed in an ADI 0.35-micrometer, SiGe process and implemented as stand-alone chip. In simulation, the peak efficiency of the PA was found to be 39%.