One-shot provides frequency discrimination

Posted on Apr 14, 2012    6184

You use a frequency discriminator to compare one signal frequency with another one. A functional feature, retriggering, of a monostable, one-shot 74xx123 multivibrator can yield frequency discrimination. Figure 1 shows a frequency discriminator that determines the relation of input-pulse frequency to a reference frequency. The external components, R1 and C1, set the reference frequency.

These values determine the 74xx123`s reference frequency as follows: fR=1/tW, and tW=kR1C1. The multiplication factor k depends on C1`s value and the power-supply voltage. The rising edge of the input pulse starts the one-shot, whose output swit

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