 ### Network # Question about Modelling the ESR of a Capacitor

K

#### K2

Hi Guys,

under:

http://www.avxcorp.com/docs/techinfo/eqtant.pdf

you can find some basics about the 'ESR' of a Capacitor.

A formula is shown describing the 'ESR' as: Rp/((2*Pi*f*Cp*Rp)^2+1)
and the 'ESC' is : Cp+1/((2*Pi*f*Rp)^2*Cp)

I guess, that the basic model looks like this:

|| __________ __________
--------o----------||--------o-----|__________|-------|==========|----
| || Cp | Rs Ls
| ___________ |
|---|___________|----|
Rp

My first Questions:

Is the formula for the ESR correct??
Paralleling Cp and Rp should result into an impedance of:
Rp/sqrt(1+(2*Pi*f*R*C)^2)

Or NOT????

My second Question:

I don't have a glue how the 'ESC' has to be calculated at all.
What is the idea behind that?

So long

Karsten

J

#### John Larkin

Hi Guys,

under:

http://www.avxcorp.com/docs/techinfo/eqtant.pdf

you can find some basics about the 'ESR' of a Capacitor.

A formula is shown describing the 'ESR' as: Rp/((2*Pi*f*Cp*Rp)^2+1)
and the 'ESC' is : Cp+1/((2*Pi*f*Rp)^2*Cp)

I guess, that the basic model looks like this:

|| __________ __________
--------o----------||--------o-----|__________|-------|==========|----
| || Cp | Rs Ls
| ___________ |
|---|___________|----|
Rp

My first Questions:

Is the formula for the ESR correct??
Paralleling Cp and Rp should result into an impedance of:
Rp/sqrt(1+(2*Pi*f*R*C)^2)

Or NOT????

My second Question:

I don't have a glue how the 'ESC' has to be calculated at all.
What is the idea behind that?

So long

Karsten

ESR = Rs.

I have no idea what ESC stands for.

Avoid tantalums. They tend to explode.

John

P

#### Phil Allison

"K2"
http://www.avxcorp.com/docs/techinfo/eqtant.pdf

you can find some basics about the 'ESR' of a Capacitor.

A formula is shown describing the 'ESR' as: Rp/((2*Pi*f*Cp*Rp)^2+1)
and the 'ESC' is : Cp+1/((2*Pi*f*Rp)^2*Cp)

** The formulae applies to fig 4 which shows a perfect capacitor in
parallel with a resistor.

I guess, that the basic model looks like this:

|| __________ __________
--------o----------||--------o-----|__________|-------|==========|----
| || Cp | Rs Ls
| ___________ |
|---|___________|----|
Rp

** No.

Fig 4 does not show what you drew.

My first Questions:

Is the formula for the ESR correct??

** For the case shown in of fig 4 only.

My second Question:

I don't have a glue how the 'ESC' has to be calculated at all.
What is the idea behind that?

** To make the parallel and serie scircuits bahave the same at the frequency
of interest.

Same impedance and same phase angle.

........ Phil

J

#### Jean-Yves

K2 said:
Hi Guys,

under:

http://www.avxcorp.com/docs/techinfo/eqtant.pdf

you can find some basics about the 'ESR' of a Capacitor.

A formula is shown describing the 'ESR' as: Rp/((2*Pi*f*Cp*Rp)^2+1)
and the 'ESC' is : Cp+1/((2*Pi*f*Rp)^2*Cp)

I guess, that the basic model looks like this:

|| __________ __________
--------o----------||--------o-----|__________|-------|==========|----
| || Cp | Rs Ls
| ___________ |
|---|___________|----|
Rp

My first Questions:

Is the formula for the ESR correct??
Paralleling Cp and Rp should result into an impedance of:
Rp/sqrt(1+(2*Pi*f*R*C)^2)

Or NOT????

My second Question:

I don't have a glue how the 'ESC' has to be calculated at all.
What is the idea behind that?

So long

Karsten

some beginning of the answer... :
http://members.ozemail.com.au/~bobpar/k7214.pdf

regards,

P
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