Re: gEDA-user: ESR of 2.2u ceramic capacitor

[John Doty <jpd@xxxxxxxxxxxxx>]

On Feb 25, 2006, at 1:39 PM, Karel Kulhavy wrote:

> What does it mean? That the capacitor loses capacity when switching
> between charge and discharge?

Yes. If you start with your 2.2 µf capacitor discharged, charge it up  
to a volt, it might take the full 2.2 µC it's supposed to. But then  
discharge it to zero volts, you might only get 2.1 µC back! The  
charge doesn't disappear (averaged over many cycles the net DC  
current will be zero), but in general when you push charge in with  
voltage, the capacitor pushes back with less voltage when it's  
discharging. That's a net energy loss to the circuit, dissipated as  
heat. A "Q meter" will register this as resistance, but it's not  
ohmic, and may not have the same effect as ohmic resistance on  
circuit operation.

> Like riding a snowboard with loose boots
> and switching edges?

Sounds about right. I'll have to ask my daughter: she's the  
snowboarder. In my day we only had these skinny pairs of things  
called "skis" ;-)

John Doty              Noqsi Aerospace, Ltd.
jpd@xxxxxxxxxxxxx