Electronics > Beginners

Ripple current / voltage, what is too much?

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FriedMule:
Wow thanks a LOT!!

I have tried to use LTSpice but it do seem hard to use I think.

Sorry for my questions but a drop of 2V or more, that will go t heat, right?

Dave tells that the FET solution mean that you can get wary high caps-"multiplication" since it don't use any current on the gate and therefor the resistor can be wary high.

So the resulting ripple is about 1.2 mV?
If I drop the FET and use two BJT in one of the configurations, that should give less heat, but also the same ripples?
Can I get even better data in both heat and ripple with other solutions?

T3sl4co1l:
Note that the output resistance is 1/Gm, or around an ohm for typical MOSFETs at typical load currents.

Output resistance is defined as a change in voltage for a change in (load) current.  So, you will get ripple voltage produced from a ripple-current-drawing load.

Tim

mvs:

--- Quote from: FriedMule on October 25, 2018, 06:58:02 pm ---Sorry for my questions but a drop of 2V or more, that will go t heat, right?
--- End quote ---
Yes, its linear circuit, P=U*I.


--- Quote ---So the resulting ripple is about 1.2 mV?
--- End quote ---
No, it is only after cap. multiplier.
LM317 does some ripple rejection too... Voltage regulators have PSRR typicaly at least 60dB (1:1000) at 100/120Hz, meaning you do not even need this cap. multiplier stage to get ripple down to few mV.

FriedMule:
Okay I se but how low do ripple have to be if I maybe want to power a sensitive chip?

Sorry I am a noob:-)

T3sl4co1l:
What chip is sensitive?

Tim

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