Schematics > Test and measurement > Frequency Comparator
Frequency ComparatorThis circuit uses a 74HCT74,
74HCT00, and a LM311 to form a frequency comparator. The two pulse trains are fed
to two D-type flip-flops (triggered by the leading edges). The flip-flops' outputs
are compared in a NAND gate. If the output of the NAND gate becomes "0", the flip-flops
are reset. If the frequency of F1 is higher than the frequency of F2, the signal
"Q2" consists of needles and "Q1" is a pulse train.
Therefore, the energy content of Q1 is higher than that of Q2.
Q1 and Q2 come via a low-pass filter (consisting of R1, R2 and C1) and are compared
by an analog comparator circuit (IC3). The comparator drives an LED and can act
as a digital output. For the case when the frequency of F1 is lower that the frequency
for F2, the signal Q1 consist of needles and Q2 is a pulse train.
Title: Frequency Comparator
Source: unknown
Published on: 2005-08-27
Reads: 327
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