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Fed_forward_low_pass_filter

2017-02-16 01:33  
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Fed_forward_low_pass_filter
This circuit allows a signal to be rapidly acquired to final value, but it provides a long filtering constant. Such a characteristic is useful in multiplexed data-acquisition systems, and has been used in electronic infant-weighing scales, where fast, stable readings of weight are needed (in spite of motion on the scale platform). The point at which the filter switches from a short to a long time constant is set by the 1-kΩ pot. Normally, this is adjusted so that switching-occurs at 90% to 98% of final value. However, the waveforms shown in Fig. 7-45B were obtained at a 70% trip point to show circuit operation. National Semiconductor, Linear Applications Handbook, 1991, p. 835.