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[Slightly off-topic request]
Hi. As of the other post of mine, another part of my weekend was spent trying to get a XOR gate to oscillate with a XTAL. I have a working 74HC14 oscillator: "One gate of a 74HC14. 470ohm resistor from gate output to the parallel of 1Mohm//XTAL. 10pF and 33pF (from the junkbox) capacitors to ground on each side of the XTAL." Since my project calls for a frequency doubler, which I want to implement with a XOR gate, I wanted to use one XOR gate of a 74HC86 as oscillator. Remaining gates would work as buffer, delay line, digital mixer. (I have Googled newsgroups and found an interesting discussion about XOR frequency doublers, so I am aware of its limitations.) So I moved the oscillator circuitry (R; C; R, XTAL; C) from the 74HC14 to the 74HC86, pulling the other input of the XOR gate to "1", so that I would produce an inverter. Nothing happens. I used a 10.0 MHz XTAL. I understand that the 74HC14 has Schmitt trigger inputs and that a 74HC86 might have higher propagation delays. Still, is it possible to use a XOR gate as an inverter and oscillator? Do I overlook something? In the end I recovered the 74HC14 oscillator, but this adds one component to the final circuit I have in mind that wastes energy, space and is underutilized. Looking forward to your always helpful replies! Paolo IK1ZYW |
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