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Question about low value capacitor charging

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Kevin Weddle

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capacitor charging

When using a low value capacitor, a nonlinear situation can occur. Each value of the signal produces a DC charging because the RC is very short. For a signal to stay proper, it must charge and discharge the capacitor on the most linear portion of the charging curve.
 

Re: capacitor charging

I didn't understand the purpose of your post: is this a question or you are stating something ?

Regarding the post itself, you never have "nonlinear situations" with linear components, such as resistors, capacitor and inductors.
 

Re: capacitor charging

It is for this reason the capacitor will distort a square wave and not pass it.
 

Re: capacitor charging

You will have a first order circuit. The output is the result of a first order differential equation circuit. It is evident that for a square wave with frequency similar to the inverse of the time constant RC, the wave form will be distorced (its the integral or derivative of the input) for high frequency the pulse will pass of from the RC circuit. It is the same problem that you have in the input of an osciloscope in AC mode.

bastos
 

Re: capacitor charging

Kevin Weddle said:
a nonlinear situation can occur.

instantenos current in cap is C*(dV/dt). Voltage is the integral. Resistance theoretically is a constant.

Operations like derivation and integration are fully linear. Hope this helps
 

Re: capacitor charging

I think you have confused yourself on the definition of a linear system.
Refer to **broken link removed** for a refresher course. As others have mentioned, resistors, capacitors and inductors are fully linear components.
 

Re: capacitor charging

The square wave is low pass filtered, i.e., its high frequency components are attenuated. If you are familiar with the Fourier theory you know what this means. This is a completely linear operation.

I know it is common to say that the square wave is "distorted", and this can surely lead to confusion. Here, "distorted" means "changed", but this does NOT mean that the RC circuit causes distortion, which is a very well defined concept in electrical circuits.

You can refer to the material indicated by the other guys.
 

Re: capacitor charging

Linear charging is the process where the rate of charge is constant and not variable. Distortion is what happens when the input signal does not mimick the output signal. Such as when a square wave is filtered because of the capacitor. We don't want to change the signal when we pass it through a capacitor.
 

Re: capacitor charging

The point is that there is NO "nonlinear situation", as you state on your first post.
 

Re: capacitor charging

checkmate said:
I think you have confused yourself on the definition of a linear system.
Refer to h**p://aurora.phys.utk.edu/~forrest/papers/linear-systems/ for a refresher course. As others have mentioned, resistors, capacitors and inductors are fully linear components.


It makes sense to me.
 

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