HCT crystal oscillator

HCT crystal oscillator: The wide frequency range, low power consumption and well-defined switching levels of HCMOS inverters make these devices eminently suited to building quartz crystal oscillators with 171. compatible outputs. Here, the six cares in a 74HCT04 package are used to build three crystal oscillators. The only difference between the 2 MHz, -16 MHz and 24 MHz oscillators is the capacitance around the quartz crystal., which in all cases must be a type that resonates at the fundamental frequency: overtone crystals cannot be used here.

For output frequencies, ƒo, other than the ones used here, use the following design data:
C2 = 723 / ƒo;

C1= C2 / 4.
where ƒo is in MHz and C1, C2 in pF. For 1-MHz crystals with a high impedance:
C1 = C2 / 10.
When one of the oscillators is not built, make sure to fit a wire link in PCB position C 1, C3 or C5. This ensures a low level at the input of the first oscillator gate, preventing high current consumption and spurious oscillation of the HCT04.

HCT crystal oscillator Schematic diagram

HCT crystal oscillator Schematic diagram

Parts list
Resistors:

R1, R3, R5 = 10 M Ω

R2, R4, R6 = 220  Ω

Capacitors:

C1 = 82 pF

C2 = 330 pF

C3 = 12 pF

C4 = 47 pF

C5 = 5.6 pF

C6 = 22 pF

C7= 100 nF
Integrated circuits:

IC 1 = 74HCT04
Miscellaneous:

X1 = crystal 2 MHz

X2 = crystal 16 MHz

X3 = crystal 24 MHz

HCT crystal oscillator Schematic diagram

HCT crystal oscillator Schematic diagram

HCT crystal oscillator Schematic diagram

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