Chapter 4 - Do I Filter Now, Later or Never?

Abstract

The chapter defines the analog, low-pass filter design parameters. These definitions apply to passive and active filters. One can build passive filters with resistors, capacitors, and/or inductors. The components of active filters are operational amplifiers, capacitors, and resistors. The chapter discusses the frequency characteristics of a low-pass filter with some reference to specific filter designs. The chapter discusses low-pass filter designs, and defines the approximation types, such as Butterworth, Bessel, and Chebyshev. The techniques used when determining the appropriate filter design parameters of an active anti-aliasing filter are also described in the chapter. The chapter explains the aliasing theory, and explores the examples of passive and active low-pass filter circuits. The chapter discusses the applications and designs the appropriate filter for an RTD temperature sensing circuit, a circuit with an analog multiplexer before the filter, and a precision light sensing circuit. The frequency domain specifications of a low-pass analog filter use four parameters: fCUT-OFF, fSTOP, AMAX, and M.