This circuit is a
phase-locked loop (PLL)
dual-frequency precision oscillator.
The main
component of this circuit is the LM567, a
general
purpose tone decoder designed to provide a 'low' TTL output at pin 8
when the input signal present at pin 3 is within the specified pass
band. External components are used to independently set the center
frequency, bandwidth and output delay of the LM567.
The LM567 has
an internal voltage-controlled oscillator that generates a fundamental
frequency fo = 1(R1C1) Hz. If this is used as input to pin 3, the
pin 8 output will be toggled at a rate that's twice fo. Thus, this
precision oscillator circuit provides two outputs to the user - one at
the fundamental frequency fo defined by R1 and C1 and another at a
frequency equal to 2 fo.
See
also:
Phase-Locked Loop IC's
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