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Not getting oscillation as per circuit given

Angy15

Nov 18, 2015
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Nov 18, 2015
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I am trying to generate oscillation to calculate rise time,fall time using circuit given. What change I have done is replaced inveter with SN74LS14. But I am not getting output .Crystal used is FX135A-327 .Any idea why its not working .
Should I change Load capacitance from 22pf to 12.5 pf.Is IC SN74LS14 correct for this testing.
 

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¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
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That circuit uses a 74LVC1GU04. Why do you think you can replace that with a 74LS14?

Those 2 chips have more differences than similarities.

- TTL vs CMOS
- 1 gate vs 6
- Schmitt trigger vs normal input
- buffered vs unbuffered
- significantly different input voltages and currents
- significantly different output voltage and drive characteristics.

My reccomendation is that you try something closer to what is suggested. You may be able to get away with a 74HC04 if you are careful with the other inputs
 

Colin Mitchell

Aug 31, 2014
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By the time you put 22p in parallel with 22p and 330k you are going to have an RC oscillator below 32kHz.
 
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