DIGITAL_FREQUENCY_DETECTOR

Published:2009/7/6 2:32:00 Author:May | From:SeekIC

A simple inventer and NAND gate can be connected to yield a highly compact and reliable digital frequency detector. This circuit can detect frequencies up to 3 MHz with 50% duty cycles. When a frequency, fi, appears at the input, points A and B detect a logical high dc level. Thereupon point E increases the latch sets and the LED lights. If the input frequency is absent and if the voltage is either at a constant high or low level, points A and B will be complementary and point E will decrease. This will reset the latch and extinguish the LED.



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