FILTERING APPLICATIONS OF FIELD PROGRAMMABLE ANALOG ARRAYS

Abstract

A Field Programmable Analog Array (FPAA), built in CMOS technology, contains uncommitted operational amplifiers, switches, and capacitors. A FPAA containing banks of programmable switched capacitors (SC) can be used to build filters for analog signals as well as a large number of diverse analog applications. The parameters of a given application, such as a filter, are functions of the capacitor values. Manufacturing and quantization errors may result in capacitor values in the FPAA other than those required by the application. For an FPAA to be a viable substitute for dedicated devices we must examine the error performance of the implementation. Such performance analysis can be built into the software to provide circuit designers with additional information. A methodology is described for determining a bound for the filter error as a function of capacitor errors and capacitor sizes. An example of detailed analysis for a low pass filter is included. Measurements of a low-pass filter implemented using Motorola's prototype FPAA compared favorably with the model predictions.