TTL_STATE_PROBE

Published:2009/7/2 21:13:00 Author:May | From:SeekIC

Uses voltage drop of LED in Schmitt trigger to indicate high, low, opencircuit, and pulse-train conditions at probe input. Indicator is Monsanto MV5491 dual redgreen LED package. High input saturates Tr1, cuts off Tr2, and turns on red LED. Low inputcuts off Tr1, and turns on green LED. For high impedance at input, both LEDs are off. Rectangular waves up to about 1 MHz turn on both LEDs, with relative brightness giving rough indication of mark-space ratio.-J. C. Flower, Logic Probe, Wireless World, Sept. 1976, p 72.



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