VARIABLE_HYSTERESlS_SCHMITT

Published:2009/7/2 4:18:00 Author:May | From:SeekIC

Uses standard 555 timer with only five additional components to give fully TTL/DTL-compatible Schmitt trigger that responds to slow input ramps as well as straight DC levels. When input is 0, output goes high and tums on Q1. When input increases to 5.8 V, output goes low and Q1, tums off. Decreasing output to 4.7 V (lower threshold point) makes output high again. For values shown, hysteresis is thus 1.1 V. Threshold points and hysteresis value can be adjusted as required by changing zeners used.-M. K.Lalitha and P. R. Chetty, Variable-Threshold Schmitt Trigger Uses 555 Timer, EDN Magazine, Sept. 20, 1976, p 112 and 114.



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