F
Fred Bloggs
- Jan 1, 1970
- 0
No not KISS. Didn't you read my OP? I wanted to go passed the simple
cases that everyone talks about and delve deaper. I was taught the
calculation method for input impedances and have used it before but
then I started questioning how voltage and current sources would be
dealt with. Then I realized that I could make circuits (like the
simple one I posted) that would not have a contast Vin/Iin ratio. This
is why I wanted a more STRICT definition of input impedance.
Although I'm a Computer Science student, I do understand Thevenin and
Laplace from my EE course. Thevenin applies to output impedances, and
the method has specific treatments for voltage/current sources when
looking BACK into a circuit. But I always wondered the method required
to treat voltage and current sources for looking INTO a circuit (INPUT
IMPEDANCE). V/I for this circuit is not constant, but other posters
have noted that in such a case we only worry about the incremental
effect on I for each Volt (which is the same result you get if you
short voltage sources and open current sources - much like when
calculating Thevenin output impedances).
Your problem is that you are thinking too much and not paying attention
to the obvious. You have been short changed by the university if they
allowed you to walk out of a networks course with your level confusion.
The Thevenin/Norton reduction theorems say no such thing about an
input/output orientation, the theorems statements are about *equivalent*
two terminal networks. When the equivalent network contains an active
source then it obviously makes no sense to talk about the terminals
being an input or output because it can dissipate as well deliver
energy, isn't that right. The equivalent impedance is an input impedance
when you zero the internal source and it's an output impedance when you
zero the external sources, then let the superposition theorem take it
from there. So you seem to be missing the fact that a single network
port can be an input and output simultaneously. Vin/Iin reduces to a
constant only when Vin is the only source.