[SOLVED] Active Devices & Passive Devices

[tahir4awan]

Someone replied for the question what are active and passive devices. The answer was,

"Active devices : the devices in which the electron flow( current) can be controlled electrically.

Passive devices : the devices where electron flow ( current ) cannot be controlled electrically.

Linear and Nonlinear generally applies to Active devices, even if there is no Passive device perfect linear.

Following the above definition, diode is an Active device."


It is confusing that many people say that diode is an active device while some say that it is a passive device because there is now control pin in diode.

what do you thing is diode an active or passive device?

 

[darkseid]

Diode is an active device as it can alter a signal. Moreover, we need to bias a diode (provide external power) in order to operate it.

 

[LvW]

I consider the answer to such a question (passive/active) as not too important.
However, to me the diode is a passive device. According to my understanding (and my personal philosophy) the main property of an active device is the ability to amplify. But - as mentioned above - it's not so relevant.

 

[Andrew8611]

A diode is a passive element, beacuse it needs an external source to operate, but as they say it is not very important.

 

[krishna1234]

diode is an active device because it can alter the signal.it respond differently for positive and negative voltages.but a passive elements like resistor responds same for both positive and negative voltage levels, and it can't alter a signal.

 

[LvW]

diode is an active device because it can alter the signal.it respond differently for positive and negative voltages.but a passive elements like resistor responds same for both positive and negative voltage levels, and it can't alter a signal.

I recognize the above as your personal definition. OK?
Or did you find something similar in any textbook?

 

[krishna1234]

I recognize the above as your personal definition. OK?
Or did you find something similar in any textbook?

so many textbooks are mentioning it............
it is not my personal definition
by definition passive elements can't alter a signal but diode alter the signal so it is an active device.

 

[sweetchoto]

Passive device: Passive device is that device which needs external source of excitation,without it it would do nothing except laying passively in the circuit or anywhere. Antenna is a big example of a passive device as it will not radiate anything unless being fed or disturbed by some external source.

Active Device: Active devices are those for which it is not a must to have external source of excitation as they can produce power(roughly) or alter a signal on their own.

I totally agree with krishna that diode is an active device,there is not a single text book/article where i have seen it being described as passive device.

"The main property of an active device is the ability to amplify",its not always true. The main property of an active device is that it can radiate energy on its own without any external source of excitation.

hope it helps.
/SC

 

[FvM]

I notice, that most text books classify all kind of semiconductor diodes as active devices, some are however discussing those with amplifier properties (e.g. Gunn diodes) explicitely as active diodes (e.g. Meinke/Gundlach Taschenuch der Hochfrequenztechnik). I however completely agree with LvW, that the classification is not so relevant, and in my opinion, almost arbitrary.

I think, that the arguments given by various contributors, why diodes have to be considered active devices are not really convincing and apply to a wide range of non-linear passive components as well. All in all, the classification of diodes is more a matter of convention than something, that clearly derives from their properties.

The main property of an active device is that it can radiate energy on its own without any external source of excitation.

Seems not understandable anyhow. Please explain in case of a diode...

 

[alexan_e]

Passive device: Passive device is that device which needs external source of excitation,without it it would do nothing except laying passively in the circuit or anywhere. Antenna is a big example of a passive device as it will not radiate anything unless being fed or disturbed by some external source.

Active Device: Active devices are those for which it is not a must to have external source of excitation as they can produce power(roughly) or alter a signal on their own.
How is a transistor different from an antenna in a circuit without any kind of signal of power supply
/SC

I don't get that, take for example a transistor, what does it do if you don't give it proper signal/supply, it is "lying passively in the circuit" , the same as a resistor , according to your definition this is a passive component too.
Actually the only active components would be a solar panel, a generator and in general any device that can create electrical power power.
A resistor can also "alter a signal on their own", they attenuate it, does this make it an active device?

According to wikipedia:

A passive component, depending on field, may be either a component that consumes 
(but does not produce) energy, or a component that is incapable of power gain.
A component that is not passive is called an active component.

according to that definition, diode is a passive component.

Alex

 

[LvW]

Quote sweetchoto: I totally agree with krishna that diode is an active device,there is not a single text book/article where i have seen it being described as passive device.

I can name you at least a hand full of textbooks. For example, here are two excerpts from Horowitz/Hill (The art of electronics):
1.) "diodes ....are passive - meaning that they don't have a built-in source of power ".
(In this context, I think a good indication for passive/actice could be the fact if the corresponding spice macro model contains a controlled source or not).

2.) "an active device can amplify and produce an output signal with more power in it than the input signal. The additional power comes from an external source of power power supply)".
________________________________________________________

Quote krishna: by definition passive elements can't alter a signal but diode alter the signal so it is an active device.

Again the question: your own definition? By the way: can a resistive voltage divider "alter a signal"? Whaz about thermistors and PTC's ? What does your definition say?
_________________________________
LvW

---------- Post added at 17:16 ---------- Previous post was at 17:15 ----------

 

[alexan_e]

tahir4awan,
I think you have opened Pandora's box, we have entered an endless loop and each one of us
tries to convince everyone else that what he thinks or read is correct.

The bottom line as noted in a few posts earlier is that it doesn't matter if a specific component is active or passive,
you choose a component for a specific task according to the properties it has which are very well documented.

Alex

 

[LvW]

I agree with Alex. It's a good "final word".

 

[tahir4awan]

What I understand of Active Devices is simply "They have Ability to control electrons (signal) with or without external signal" so diode is an active device.
Passive devices don't have ability to control though they can alter the signal like capacitors and inductors but they don't have control over signal.

 

[FvM]

It's your choice to join one of the arbitrary definitions of an active device, that has been given in the previous discussion. I think, they won't get you anywhere, except for collecting some stuff, that can be reproduced in an examination, if your professor likes it simple.

The underlying assumptions can be mostly refuted. You can make a passive component, e.g. an inductor, "controlling a signal" and operate as an amplifier, powered from an external source. More generally, any electronic device exposing a non-linear characteristic has an ability to get active this way.

P.S.: Do you think, that an electric bell, a kind of electromagnetical oscillator, is an active or a passive device? Electric bell - Wikipedia, the free encyclopedia

 

[tahir4awan]

I don't think that electromagnet bell is an active device because electromagnet does not control electrons but it simply produces magnet field so there is no control of electrons in this device. Electromagnet bell is simple an electrical and mechanical arrangements so that device work in a specific way.

 

[FvM]

I guess, you didn't look for the operation principle. Of course the switch involved in the electric bell controls electrons when it switches the current on and off.

 

[keremcant]

diode is an active device because it can alter the signal.it respond differently for positive and negative voltages.but a passive elements like resistor responds same for both positive and negative voltage levels, and it can't alter a signal.

what is meant by altering, I mean a capacitor or an inductor can also alter a signal.

I guess the thing is the necessity of an external power supply. what I mean is to make an op amp work even if you will not amplify anything or whatever, you have to supply power to it. but in the case of a capacitor or inductor you don't need external sources.

so from this point of view diode is also a passive component, because it doesn't need any external resources.

 

[LvW]

.....................
so from this point of view diode is also a passive component, because it doesn't need any external resources.

100% correct.

 

[tahir4awan]

The controlling of electrons by switch is not same as control of electrons by active devices.
Switch is just opening and closing circuit. If you think that switch is controlling electrons then rheostat is also a control device. What would you name the rheostat ? an active device? definitely not.