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Author Topic: 40106 (hex inverter) as oscillator  (Read 2346 times)
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so I wanted to make a pierce oscillator with the 40106 and a 6MHz crystal. I hooked it up just like the wikipedia article :


now the thing that's boggling me is that when I remove the caps and crystal, it still oscillates(at a slightly higher frequency)! how does this make any sense? A 40106 with a resistor bridging the input and output just oscillates all on its own?

The purpose of the oscillator is the clock input on a 4040 binary counter. I hooked up the 12th stage to an oscilloscope and it reads 1.2KHz, so I guess the inverter is oscillating at around 5MHz. Is there any harm to the 40106 in doing this?
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Sure, it makes sense! Think about it: you are feeding the output of an inverter back to the input. So the output is 0, when presented at the input it makes the output 1, when presented at the input it makes the output 0, etc. The oscillation frequency will be related to the propagation delay from input-to-output of the inverter as well as the rise time of the input, determined by the feedback resistance and capacitance of the inverter's input.

Certain technologies (like the CD4xxx series) seem to work well with this concept, as does 74HC, but others do not and they will settle upon some intermediary steady DC value instead of oscillating.

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Well that makes sense, I just thought you needed something like this

 as a bare minimum. But I guess what that really does is control the frequency. thanks for the reply!
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so I wanted to make a pierce oscillator with the 40106 and a 6MHz crystal. I hooked it up just like the wikipedia article :


now the thing that's boggling me is that when I remove the caps and crystal, it still oscillates(at a slightly higher frequency)! how does this make any sense? A 40106 with a resistor bridging the input and output just oscillates all on its own?

The purpose of the oscillator is the clock input on a 4040 binary counter. I hooked up the 12th stage to an oscilloscope and it reads 1.2KHz, so I guess the inverter is oscillating at around 5MHz. Is there any harm to the 40106 in doing this?

YESSSSSSS , IS JUST OSCILLATES ,USING THE PARASITIC CAPACITANCE
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