You can call it generalized Ohm's law.
There is a vicious rumor that diodes are not resistors, but they are resistors. They are nonlinear resistors (if we neglect the dynamic parasitics, of course and assume the exponential curve in the VI plane is what characterize them).
If you need to invoke the principle of authority to defend this assertion, you can always quote Chua, Desoer, Kuh, "Linear and Nonlinear Circuits". This is what I call "THE bible of circuit theory". It's not some high school or vocational school textbook for courses limited to the easiest circuits.
Well, up to a few posts ago, "nonlinear resistor" was an oxymoron, so it's progress.
Try this. Go here: https://automobiles.honda.com/ (or any other car manufacturer) and try to find a Formula1 race car for sale.
If you can't find it then Formula 1 race cars are not cars.
Helen is a woman, even if you don't find it in the list of women whose name starts with K, like Kate.
Just for entertainment value?Yes.
non linear system has linear approximation around a small operating point....
STOP THE PRESSES!
... oh wait, that's the underlying principle of how spice AC analysis works.
Small signal analysis has nothing to do with what we are discussing here.
The resistance I talk about is the static resistance, not the dynamic or incremental resistance of small signal analysis.
Try again.That was your long winded and dithering proof:So, we are now seeing the diode as a voltage dependent resistor. Let's see... what is the resistance 400mV? Let's zoom in:
[MASSIVE IMAGE]
I'd say it's about 23.2 kohm.
Let's see what is the resistance at, I don't know, 660 mV (about 5mA of diode current). We can compute it by hand of course, but on the graph we see it is 132 ohm.
[MASSIVE IMAGE]
Now, let's see if we can make something with these values...
[snipping conversational fluff]
Ok, exact same results, if we neglect a bit of rounding error in reading and setting the values.
Now, take your black boxes out of the fridge. Put the diodes D1 and D2, and the resistors R1 and R2 inside a black box each. Shuffle them around. And tell me: without looking inside the black boxes and without resorting to second order effects (like temperature dependence, or changing the other circuital parameters to change the operating points) can you tell me which are the diodes and which are the resistors, by simply measuring voltages, currents and powers?So to try and claim you're not relying on the well known small signal AC parameters is plainly incorrect.
If you dont like relying on small signal characteristics, perhaps "try again" with your explanation/justification.
Again, small signal analysis has nothing to do with anything I have written in that post.
Nothing.
I zoomed in on the V-R characteristic to find an accurate value of the static resistance. Not the dynamic, or incremental, or small signal resistance.
Then I used the static resistance at a chosen voltage or current to choose the limiting resistor that would have set the chosen operating point.
Then I showed that using a resistor with the correct static resistance value would give the same variables in the circuit..
If you want to waste a bit of time you can create in LTspice a voltage controlled resistor that has the same R=R(V) dependence of a 1N4148. You will then see that it will behave (secondary effects apart) as a diode, confirming that it's the variable resistance. that gives a diode its behavior.
Go ahead and try.
To the OP.
Are you sure you are talking about a 'normal' diode, and not a 'special' type of (apparently chaotic) diode?
Oh new words and definitions to play with. How about we take the IEEE dictionary as the authoritative reference:
static resistance (semiconductor rectifier device) (forward or reverse) The quotient of the voltage by the current at a stated point on the static characteristic curve.
small-signal resistance The resistive part of the quotient of incremental voltage by incremental current under stated operating conditions.
small-signal A signal which when doubled in magnitude does not produce a change in the parameter being measured that is greater than the required accuracy of the measurement.
As I said in my opening statement, you're just playing with small signal analysis a well known and entirely un-novel method. There is nothing interesting here as most anything can be described as a small signal resistor (with bounds on some other dimension). So you're still wrong and trying to twist definitions to your liking while ignoring the consensus and the established science.
From: A.C. Fischer-Cripps, in Newnes Interfacing Companion, 2002
3.3.7 Log amplifier
A non-linear resistor is connected into the feedback circuit. In practice, this can be a diode, but a transistor connected as a diode is used since the forward biased transfer function is more accurately exponential. The exponential nature of the forward biased diode leads to a logarithmic decrease in gain of the circuit as the input signal is increased.
A non-linear resistor is connected into the feedback circuit. In practice, this can be a resistor, but a resistor connected as a resistor is used since the forward biased transfer function is more accurately exponential. The exponential nature of the forward biased resistor leads to a logarithmic decrease in gain of the circuit as the input signal is increased.
Oh new words and definitions to play with. How about we take the IEEE dictionary as the authoritative reference:
static resistance (semiconductor rectifier device) (forward or reverse) The quotient of the voltage by the current at a stated point on the static characteristic curve.
Yes, this is the only one I have used. Did you not realize it?Quotesmall-signal resistance The resistive part of the quotient of incremental voltage by incremental current under stated operating conditions.
small-signal A signal which when doubled in magnitude does not produce a change in the parameter being measured that is greater than the required accuracy of the measurement.
As I said in my opening statement, you're just playing with small signal analysis a well known and entirely un-novel method. There is nothing interesting here as most anything can be described as a small signal resistor (with bounds on some other dimension). So you're still wrong and trying to twist definitions to your liking while ignoring the consensus and the established science.
No, I have not used small signal analysis. Where did you study small signal analysis? You are mistaken. Please seek tutoring from someone you trust to straighten this out.
Notice that they didn't write this:QuoteA non-linear resistor is connected into the feedback circuit. In practice, this can be a resistor, but a resistor connected as a resistor is used since the forward biased transfer function is more accurately exponential. The exponential nature of the forward biased resistor leads to a logarithmic decrease in gain of the circuit as the input signal is increased.
In order to be able to use nonlinear resistors effectively in a practical design, it is necessary to understand some basic properties.We will illustrate these properties by considering a prototypical example of a nonlinear resistor, the pn-junction diode (henceforth referred to as diode). Although we model diodes as nonlinear resistors, they are so important in circuit theory that they have their own symbol[...]
In order to be able to use nonlinear resistors effectively in a practical design, it is necessary to understand some basic properties.We will illustrate these properties by considering a prototypical example of a nonlinear resistor, the pn-junction diode (henceforth referred to as diode). Although we model diodes as nonlinear resistors, they are so important in circuit theory that they have their own symbol[...]
Ok, it really is basic comprehension of inclusion.
This is a set of...
of...
...nonlinear resistors!
Yeahhhhh!
Now take this big huge set of nonlinear resistors, and put it near the set of linear resistors (they also have their own symbol).
What have you got now? What is the set formed by the set of linear and nonlinear resistors?
It's a set of...
...
Resistors!
Yeahhhh!
QuoteThey are not. The resistor is the industry standard term for a device that is designed to create the effect of resistance in a well defined manner. While electrical resistance is a physics phenomenon where something opposes the flow of current in a electrical circuit.
What is the point you are trying to make with this thread? That a diode has electrical resistance? Or that everything that exhibits electrical resistance should be called a resistor?
I am trying to uncover the roots of this cognitive dissonance. First you say that varistors are resistors that... And then you say no, they are not resistors, because resistors are only linear.
Go on that Vishay page that shows how to simulate nonlinear resistors (a term that up to a few messages ago you people thought I had invented, LOL) and simulated your resistor with an exponential characteristic. There you have your diode. It is a nonlinear resistor.
From: A.C. Fischer-Cripps, in Newnes Interfacing Companion, 2002
3.3.7 Log amplifier
A non-linear resistor is connected into the feedback circuit. In practice, this can be a diode, but a transistor connected as a diode is used since the forward biased transfer function is more accurately exponential. The exponential nature of the forward biased diode leads to a logarithmic decrease in gain of the circuit as the input signal is increased.
There's no reason why you couldn't call every 2-leaded device as a resistor:
- A diode is a non-linear resistor that conducts current exponentially with applied voltage, and only in one way
- A capacitor is a giga-ohm resistor with two electrodes that conducts through dielectric materials, it also happen to store charge too.
- An inductor is a low-value resistor made with coils of copper wire wrapped around something, that also happens to store energy in the magnetic field.
You can invent your own method of describing a circuit. You can invent your own mathematical system. You can invent your new language. We simply agreed on what we commonly use to get everyone on the same page, and not having to explain everything from scratch every single time.
(Pure) Resistors, (Pure) Capacitors, (Pure) Inductors