Floyd L. Davidson wrote:
ehsjr wrote:

wrote:

ehsjr wrote:


wrote:

The L and the C don't care about your
DC offset, so you must still think of the signal as AC in order to
understand their behavior. They don't care that the overall signal
doesn't reverse polarity, they only care that derivative of voltage
with respect to time is non-zero.


Er - there are cases where the L will be saturated by
the DC component.

Ed


That's about the same as pointing out that some capacitors
are polarity sensitive, and will effectively be a short
if the polarity is wrong. It's true, but does not enter
into the problem at this point.


What you are suggesting is a good issue to keep in mind for
the real
world (and one I had overlooked).
However, what you have actually said is not true.
An inductance - a specific element we both referred to as L -
will not
saturate.

You mentioned the behavior of L and C, which refers to the


Inductors saturate. Inductance doesn't.

Behavior refers to the way the component performs.
Inductance as a property - see the definition, #1 - does not
perform or saturate. Inductance as a component - see the
definition, #2 - performs, and can saturate.

snip


What I referred to is a circuit element that can saturate, as per
the definition for inductance.

http://dictionary.reference.com/search?q=inductance
"1. The property of an electric circuit by which an
electromotive force is induced in it as the result of a changing
magnetic flux.
2. A circuit element, typically a conducting coil, in which
electromotive force is generated by electromagnetic induction."


A circuit element, not a component device.

Try reading the definition, where it says "typically a conducting
coil". What circuit element do you have in mind that is not a
component but in which electromotive force is generated by
electromagnetic induction?

snip



But saturation has nothing to do with the inductance.

Huh? The inductance of a coil lowers as the current through
it drives it into saturation.

snip

After the
right inductance is calculated, then a specific device has to be
chosen, and *that* is when saturation has to be considered. So
do physical size, mounting style, insulation, and perhaps other
parameters too, none of which are related to the original
"inductance" problem.


Very specifically for the op's question,
the possibility of saturation *must* be considered, even though
the question did not include the word inductor. I think those
rules, or whatever you call them, are not correct.


Could be! I don't remember the OP's question... :-)


Maybe you should re-read it.

Ed