Using Digital Potentiometers To Design Low Pass Adjustable Filters

The most common filter found in a data acquisition system signal path is a low-pass filter. This type of filter is usually used to reduce A/D Converter (ADC) aliasing errors. If there is more than one signal that is applied to the A/D converter through a multiplexer, each signal source may have its own set of filter requirements (i.e., settling time, fast transition region, etc.). Consequently, a variety of filters may be required in the circuit prior to the multiplexer. Usually these filters are implemented with operational amplifiers (op amps) in combination with fixed resistors and capacitors.