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Adaptive Highpass Filter with Independent Gain Block
GR581 DATA SHEET
FEATURES • unity gain 12 dB/oct. highpass Butterworth filter • adaptive frequency range from 200 Hz to 2 kHz • rectifier threshold set to 82 dBSPL (adjustable) • low noise, typically 2.6 µV • 300 µA typical current drain • operates from 1.1 to 3 VDC • preamplifier with 56 dB open loop gain DESCRIPTION The GR581 is a level-sensitive, adaptive highpass filter comprised of a current controlled highpass filter, a half- wave rectifier, a voltage regulator for microphone bias and a separate preamplifier. The internal rectifier senses the long term average signal level and controls the filter response by setting the control current of the filter.