Optimal allocation of local feedback in multistage amplifiers via geometric programming

We consider the problem of optimally allocating local feedback to the stage s of a multistage amplifier. The local feed-back gains affect many performa nce indexes for the overall amplifier, such as bandwidth, gain, rise time, delay, output signal swing, linearity, and noise performance, in a complica ted and nonlinear fashion, making optimization of the feedback gains a chal lenging problem. In this paper, we show that this problem, though complicat ed and nonlinear, can be formulated as a special type of optimization probl em called geometric programming. Geometric programs can be solved globally and efficiently using recently developed interior-point methods. Our method , therefore, gives a complete solution to the problem of optimally allocati ng local feedback gains, taking into account a wide variety of constraints.