# How diode is passive component?

#### ISB123

Joined May 21, 2014
1,236
Anything that is controlled by current or voltage is active device in my book.

#### WBahn

Joined Mar 31, 2012
26,156
Anything that is controlled by current or voltage is active device in my book.
So a resistor is an active device because the current is controlled by the voltage (and vice-versa, for that matter).

#### ISB123

Joined May 21, 2014
1,236
Resistor controls the current,its resistance
doesnt change if you apply more voltage to it..Its dependant on temperature.

#### WBahn

Joined Mar 31, 2012
26,156
Resistor controls the current,its resistance
doesnt change if you apply more voltage to it..Its dependant on temperature.
If I apply more voltage I get more current.

Since current qualifies as a subset of "anything", we have an "anything" being controlled by a voltage, which satisfies your definition of an active device.

#### WBahn

Joined Mar 31, 2012
26,156
Oh, and if you want to change your definition so that it is active if and only if the device parameters change with current or voltage (so that you can exclude resistors, capacitors, and inductors), then a diode would not be active since the parameters in the constitutive equation for a diode do not depend on voltage or current. But, then again, that is also the case for a BJT transistor, so a transistor would not be an active device by that modified definition.

#### ISB123

Joined May 21, 2014
1,236
If I apply more voltage I get more current.

Since current qualifies as a subset of "anything", we have an "anything" being controlled by a voltage, which satisfies your definition of an active device.
By applying more voltage you will get more current not more resistance. So you can't change the original value of resistor to some other resistance by applying more voltage.And key purpose of resistor is to provide set resistance which wont change dependently on voltage or current.

#### WBahn

Joined Mar 31, 2012
26,156
By applying more voltage you will get more current not more resistance. So you can't change the original value of resistor to some other resistance by applying more voltage.And key purpose of resistor is to provide set resistance which wont change dependently on voltage or current.
But your definition, namely, "Anything that is controlled by current or voltage is active device," does not say that "anything" has to be restricted to the resistance of a resistor. Your definition says that it is an active device if "anything" is controlled by either current of voltage. Are you claiming that current through a resistor is not "anything"? If so, then what is and is not an "anything"?

#### ISB123

Joined May 21, 2014
1,236
It shouldn't be able to change the original purpose of the component. Do you change the resistance of the resistor if you apply more voltage to it?No. Do you change the diode junction from PN to NP if you apply more voltage across it?No.

#### WBahn

Joined Mar 31, 2012
26,156
It shouldn't be able to change the original purpose of the component. Do you change the resistance of the resistor if you apply more voltage to it?No. Do you change the diode junction from PN to NP if you apply more voltage across it?No.
Do you change any of the junctions in a transistor from PN to NP or vice-versa if you apply more voltage across it? No. So now you would seem to be saying that a BJT is not an active component.

Again, in your definition of what makes a device active, what is "anything", since it obviously is NOT actually "anything"?

Whatever your definition is going to be, when that definition is applied to a device that is universally accepted as being passive, your definition must conclude that it is passive. Similarly, when applied to a device that is universally accepted as being active, your definition must conclude that it is active. If you need to place constraints on what "anything" can mean in order to make this happen, then those constraints must be a part of the definition.

#### ISB123

Joined May 21, 2014
1,236
I'm just not going to say anything because this discussion can go to infinity and beyond.
Cheers!

#### recklessrog

Joined May 23, 2013
985
Wow!!! this discussion takes me back to when I was working on the engine control computers (analogue) for Concorde. I had to write a report about any failed components. A diode was leaky and I described it as active because at the time, my view was, as it was essential that it only conducted when forward biased, it was "actively" operating. However, I was reprimanded by a senior technician who claimed it was passive. This started a long and drawn out discussion amongst all of us and we eventually agreed it was dependent upon its application. But then we could not agree on which applications were active or passive???? and so it was never really resolved.

#### WBahn

Joined Mar 31, 2012
26,156
Wow!!! this discussion takes me back to when I was working on the engine control computers (analogue) for Concorde. I had to write a report about any failed components. A diode was leaky and I described it as active because at the time, my view was, as it was essential that it only conducted when forward biased, it was "actively" operating. However, I was reprimanded by a senior technician who claimed it was passive. This started a long and drawn out discussion amongst all of us and we eventually agreed it was dependent on its application. But then we could not agree on which applications were active or passive???? and so it was never really resolved.
I can just imagine.

It really is a gray area because, as you guys decided, the very meaning of "active" and "passive" is context-dependent. But even trying to include the context as part of the definition only helps so far for parts, like diodes, that just seem to always be close to the fence such as subtle differences in implied meaning can swing the decision one way or another.

#### WBahn

Joined Mar 31, 2012
26,156
I'm just not going to say anything because this discussion can go to infinity and beyond.
Cheers!
Understand. Please note that I am not trying to be contrary just for contrariness sake, but rather trying to help you solidify a "fluffy" definition into something that is more defensible.

Aside: What is the critter in your avatar? I know I've seen it before, but nothing comes to mind.

#### kubeek

Joined Sep 20, 2005
5,733
My definition of a passive device is one that only consumes power (attenuates the signal) and doesn't alter the signal. By this definition, a diode is definitely active, since it significantly alters the signal.
What do you mean by signal?

#### ISB123

Joined May 21, 2014
1,236
Understand. Please note that I am not trying to be contrary just for contrariness sake, but rather trying to help you solidify a "fluffy" definition into something that is more defensible.

Aside: What is the critter in your avatar? I know I've seen it before, but nothing comes to mind.
That animal is a sloth.

#### SLK001

Joined Nov 29, 2011
1,548
What do you mean by signal?
What is going into the device. Maybe I should have used "waveform".