Analog filters can be found in almost every electronic circuit. Audio systems use them for preamplification, equalization, and tone control. In communication sys- tems, filters are used for tuning in specific frequencies and eliminating others. Digital signal processing sys- tems use filters to prevent the aliasing of out-of-band noise and interference. This application note investigates the design of analog filters that reduce the influence of extraneous noise in data acquisition systems. These types of systems pri- marily utilize low-pass filters, digital filters or a combina- tion of both. With the analog low-pass filter, high frequency noise and interference can be removed from the signal path prior to the analog-to-digital (A/D) con- version. In this manner, the digital output code of the conversion does not contain undesirable aliased har- monic information. In contrast, a digital filter can be uti- lized to reduce in-band frequency noise by using averaging techniques. AN699 Anti-Aliasing, Analog Filters for Data Acquisition Systems Author: Bonnie C. Baker ANALOG VERSUS DIGITAL FILTERS Microchip Technology Inc. A system that includes an analog filter, a digital filter or both is shown in Figure 1. When an analog filter is INTRODUCTION implemented, it is done prior to the analog-to-digital conversion. In contrast, when a digital filter is imple- Analog filters ca……