As per my understanding, all the sources of electrical energy are considered to be active component.If I am right, in LC oscillating circuit, capacitor as well as inductor acts as a source asynchronously. Now, do we consider capacitor and inductor active or passive component in this case?

 

The term active does not denote a device's ability to introduce energy into a circuit. It is a more complicated concept and there are grey areas

My electronics dictionary has

"Denoting any device, component or circuit that introduces gain or a directional functio. In practice any device except a pure resistance, capacitance or inductance or a combination of these three is active"

 

But transformer is also passive component...!!!! :?

 

As per my view, active components are those which creates energy of its own and have capacity to amplify signal. But, I don't think diodes have capacity to do so. Than why is it considered as active components?

 

The AAC book states diodes are passive...

http://www.allaboutcircuits.com/vol_3/chpt_1/2.html

 

One thread will do. I will merge the two in one minute.

 

How would you classify a tunnel diode?

 

What is the purpose of making a distinction between active and passive?

 

a tunnel diode can be either. when used as a regular diode, it is passive, when it is used in its negative resistance state, it is active as an amplifier or oscilator.
a transformer is a passive componant, it dosnt change or amplify.

 

There is no reason to use a tunnel diode as a regular diode when the latter will do.

 

My preferred definition is that the only passive components are resistors, inductors, and capacitors (or variations of that, such as transformers). Thus I consider a diode an active device and don't need to split hairs about whether any other device is active or passive. But, as noted, I see no good reason to get all that concerned about an arbitrary definition.

 

FWIW, Mouser does not list diodes under "passive components". I could go either way on a diode but the dictionary definition provided by studiot seems to hold.

When the definition says "gain", would we assume they mean gain>1? A resistor divider provides a gain <1, but surely is not active.

 

The term active does not denote a device's ability to introduce energy into a circuit. It is a more complicated concept and there are grey areas

A transistor has no energy of its own, but I know of no one who would say that it is not an active component.

A photodiode reacts to incident light, and all diodes are photodiodes, if you allow light to enter the junction so it is not unreasonable to classify them as active.

Of course that brings up the question of transducers in general.
And, of course, resistors can be transducers (as in strain bridges).


Perhaps we should have a classification scheme that is more than two way?

 

A transformer can have voltage gain or current gain, but not both at the same time - power gain. This places it clearly in the "passive" category. With an external power source, a tunnel diode can produce sustained oscillation, something no LC combination can do, so I see it as an "active" part. In fact, I mildly disagree with the AAC book about all diodes. Semiconductor junction physics are fundamentally different from anything in the R-L-C camp, so I see all diodes as active devices. True, most don't have power gain, but Rs, Ls, and Cs are all variations of the same theme; diodes just plain ain't.

ak

 

I don't know if this is accurate, but I usually go by the model if the component can be affected by ESD then the component is active.