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    Calculate the load capacitance in oscillators

    Hi
    I am using a ring oscillator like the one attached and I am wondering how to calculate the CLoad in this case. Because I want to do some tests in stressing the circuit but I am not sure what would be a normal/relax value and what would be a stress capacitance value. I hope you could help me.

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  2. #2
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    Re: Calculate the load capacitance in oscillators

    Is it even possible to calculate the load capacitance from this?



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  3. #3
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    Re: Calculate the load capacitance in oscillators

    Each logic gate has some resistance in its output stage. This means it can provide (source) limited amount of current to the load. Your capacitor load tries to draw maximum current for the time it takes to charge. Probably in the low mA range, seeing this discussion:

    http://forum.allaboutcircuits.com/th...4ls-ttl.84712/

    In addition it makes a difference whether your capacitor is discharging since then the IC must sink current coming back through its output stage.

    Small C value rapidly charges and discharges, so the IC probably won't be terribly stressed. Large C value takes a longer time to charge so it draws current for a longer time. It won't necessarily destroy your IC but to be safe you should install a resistor to limit current.


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