circuit component parasitics

[Krish]

How can i find the a components parasitics. like for inductor, what
are the associated cap and resistor...is there any data table
approximately giving this data.

 

[[email protected]]

How can I find the components parasitics for an inductor, what
are the associated capacitance and resistance...is there any data
table approximately giving this data.

The resistance of any given inductor is usually given as such in the
manufacturer's data sheet. The parallel capacitance has to be deduced
from the self-resonant frequency of the inductor, which is often given
on the data sheet as well.

For a single layer winding, the parallel capacitance often turns out to
be of the order of one picofarad. It's much higher with multi-layer
windings.

Modelling an inductor as a single perfect inductance in parallel with a
single perfect capacitance and in series with a single perfect resistor
is often good enough, but it isn't all that realistic.

 

[Rich Grise]

Modelling an inductor as a single perfect inductance in parallel with a
single perfect capacitance and in series with a single perfect resistor
is often good enough, but it isn't all that realistic.

I'd kind of like to foment a discussion of the difference between "good
enough" and "realistic." ;-)

Cheers!
Rich

 

[Spehro Pefhany]

I'd kind of like to foment a discussion of the difference between "good
enough" and "realistic." ;-)

Cheers!
Rich

Realistic is/was a Radio Shack brand name, and it's hardly good
enough.



Best regards,
Spehro Pefhany

 

[Jim Thompson]

Realistic is/was a Radio Shack brand name, and it's hardly good
enough.



Best regards,
Spehro Pefhany

The "Realistic" brand name has been around for a VERY long time.

When we went to the minister's house to be married 45 years ago, he
had a Realistic brand "HiFi".

I wanted to go find another minister ;-)

...Jim Thompson

 

[[email protected]]

I'd kind of like to foment a discussion of the difference between "good
enough" and "realistic." ;-)

Good enough, in that it captures the behaviour that we need to model.

Unrealistic, in that it doesn't give you a clue about changing the
inductor to change the parallel capacitance - which you can do, for a
multilayer winding, by making the coil as a stack of thin multilayer
coils, rather than winding the coil as a series of cylindrical layers.

 

[Rich Grise]

Good enough, in that it captures the behaviour that we need to model.

Unrealistic, in that it doesn't give you a clue about changing the
inductor to change the parallel capacitance - which you can do, for a
multilayer winding, by making the coil as a stack of thin multilayer
coils, rather than winding the coil as a series of cylindrical layers.

Yes, Pie-wound, which I think really is "pie", and not the Greek letter
"pi". ;-)

But if the operative word here is "model," then wouldn't a lower-C
coil just be modeled with a smaller C in the model?

Or is your point that determining that C value is the hard part?

Thanks,
Rich

 

[John Woodgate]

I read in sci.electronics.design that Rich Grise <[email protected]>

Yes, Pie-wound, which I think really is "pie", and not the Greek letter
"pi". ;-)

But if the operative word here is "model," then wouldn't a lower-C coil
just be modeled with a smaller C in the model?

Or is your point that determining that C value is the hard part?

There isn't just one stray C, even for a solenoid. For a pie-wound coil,
each pie has a self-capacitance and there is also an 'end-to-end'
capacitance.

I suspect that in the ARRL Handbook you can read that a pie-wound choke
can resonate in several modes, with some pies being net inductive and
others net capacitive. Especially if you used the trick of making the
pies of different numbers of turns in an effort to get a high impedance
over a wide range of frequencies. Fun!

 

[Rich The Newsgropup Wacko]

I'd kind of like to foment a discussion of the difference between "good
enough" and "realistic." ;-)

Realistic is/was a Radio Shack brand name, and it's hardly good enough.[/QUOTE]

Come on, Mr. Speff - most of us can tell "Polish" from "polish". ;-)
--
Cheers!
Rich
------
There was a young lady from Siam
Who said to her lover, one Kiam,
"You may kiss me of course,
But you'll have to use force.
Though god knows you're stronger than I am."

 

[John Woodgate]

I read in sci.electronics.design that Rich The Newsgropup Wacko

Come on, Mr. Speff - most of us can tell "Polish" from "polish". ;-)

.... and reading from Reading.

 

[Ian]

I read in sci.electronics.design that Rich The Newsgropup Wacko


... and reading from Reading.

....but from just up the road a bit, can you tell "slough" from the
"Slough of Despond"?

Regards
Ian

;-)

 

[[email protected]]

I read in sci.electronics.design that Rich Grise

Yes, but my point is that you want to be able to change that
capacitance, and for that you need a model that gives you some idea
idea of how the lumped capacitance is built up.

I'm interested in the difference between predicting what a circuit will
do, and understanding what is going on.

There's nothing hard about measuring the capacitance after you've wound
the coil. The trick is in predicting what sort of capacitance you will
get if you wind the coil in a different way.

There isn't just one stray C, even for a solenoid. For a pie-wound coil,
each pie has a self-capacitance and there is also an 'end-to-end'
capacitance.

And this would be what you would have to capture in a quasi-realistic
model.

I suspect that in the ARRL Handbook you can read that a pie-wound choke
can resonate in several modes, with some pies being net inductive and

others net capacitive. Especially if you used the trick of making the

pies of different numbers of turns in an effort to get a high impedance
over a wide range of frequencies. Fun!

More fun than I've yet contemplated - but I've added it to my list of
projects to be attempted when I can find the right customer.

 

[John Woodgate]

I read in sci.electronics.design that Ian <[email protected]>

...but from just up the road a bit, can you tell "slough" from the
"Slough of Despond"?

Not according to John Betjeman, anyway.