Something else that's puzzled me for a good long while. May seem elementary, but maybe it isn't ...
Often one sees two caps placed next to each other, like across a power-supply rail to filter noise, spikes and ripple, like so:
**broken link removed**
It always strikes me that since the two caps are in parallel, what we really have is this:
**broken link removed**
since capacitances in parallel are simply added together (same as resistances in series). In other words, the small capacitance should be all but completely swamped or subsumed by the larger one.
But obviously this isn't the case. So isn't what we really have more a case of this?
**broken link removed**
or maybe even this?
**broken link removed**
In effect creating a "pi" filter. Otherwise, what would be the point of adding a little bitty capacitor next to a big old electrolytic, for example?
So enlighten me ...
Often one sees two caps placed next to each other, like across a power-supply rail to filter noise, spikes and ripple, like so:
**broken link removed**
It always strikes me that since the two caps are in parallel, what we really have is this:
**broken link removed**
since capacitances in parallel are simply added together (same as resistances in series). In other words, the small capacitance should be all but completely swamped or subsumed by the larger one.
But obviously this isn't the case. So isn't what we really have more a case of this?
**broken link removed**
or maybe even this?
**broken link removed**
In effect creating a "pi" filter. Otherwise, what would be the point of adding a little bitty capacitor next to a big old electrolytic, for example?
So enlighten me ...