2_20_kHz_SELF_TUNING_BANDPASS

Published:2009/7/2 8:13:00 Author:May | From:SeekIC

Center frequency of filter is automatically adjusted to track signal frequency, for optimum noise rejection when input frequency varies over wide range as it does with many types of vibrating transducers.Requires no reference frequency and no intemal oscillator or synchronizing circuits. Flequency range can be extended in decade steps by capacitor switching. When filter is not tuned to input frequency, phase shift is not 180° and phase detector applies error signal to gate of FET to control its drain-source resistance. Phase detector A4-A5-CR2-CR3 and FET form part of negative-feedback loop around filter, so error in phase changes resistance of FET and thereby retunes filter, Article gives design equations, operational details, and waveforms at various points in circuit.-G. J. Deboo and R.C. Hedlund, Automatically Tuned Filter Uses IC Operational Amplifiers, EDN/EEE Magazine, Feb.1, 1972, p 38-41.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Basic_Circuit/Filter_Circuit/2_20_kHz_SELF_TUNING_BANDPASS.html

Print this Page | Comments | Reading(3)