Author: David HarmonDate: 19:24 02-08-07
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What exactly is the definition of an "active" device? I think of it as
"capable of being used in some way to provide amplification" but that
seems horribly imprecise,
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Author: NobodyDate: 20:07 02-08-07
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On Thu, 02 Aug 2007 16:24:25 -0700, David Harmon wrote:
> What exactly is the definition of an "active" device? I think of it as
> "capable of being used in some way to provide amplification" but that
> seems horribly imprecise,
One definition is something which requires a power source distinct from
the signal.
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Author: JeffMDate: 20:56 02-08-07
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David Harmon wrote:
>What exactly is the definition of an "active" device? I think of it as
>"capable of being used in some way to provide amplification"
>but that seems horribly imprecise
Trying to define it so that a relay is excluded[1]
but semiconductors used in digital mode aren't is kinda tough.
The definition offered by "Nobody"
http://www.google.com/search?q=define:active+device ??
doesn't do a good job at that.
.
.
[1] or does someone consider a relay an active device?
Konrad Zuse perhaps?
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Author: Bob MyersDate: 21:21 02-08-07
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"JeffM" <jeffm_@email.com> wrote in message
news:1186102598.910040.275650@z24g2000prh.googlegroups.com...
> Trying to define it so that a relay is excluded[1]
> but semiconductors used in digital mode aren't is kinda tough.
> The definition offered by "Nobody"
> http://www.google.com/search?q=define:active+device ??
> doesn't do a good job at that.
> .
> .
> [1] or does someone consider a relay an active device?
> Konrad Zuse perhaps?
I think I'd have to consider a relay "active" in a broad enough
sense of that term - and I'm also having problems narrowing
it down such that it doesn't exclude some other things that ARE
commonly thought of as "active."
Some other possible definitions:
A passive device would be any which either dissipates energy,
(resistors) passes it along (ideally without change - I'm trying to
think of the right terminology to cover transformers as well as
simple conductors and such), or temporarily stores it (reactances),
with no other function; active devices are pretty much everything
that's left.
Active devices (a) require an external source of power in addition
to the signal or current being controlled or acted upon, and/or
(b) contain one or more non-linear elements (tricky, though -
"nonlinear" could be a problem when we start looking at
magnetic components with hysterisis and such.
We could, of course, just start by throwing things into bins -
all the wires, resistors, inductors, capacitors, transformers, and
simple switches go into the "passives" bin, all the transistors, tubes,
diodes, and ICs go into the active, and we leave anything not yet
covered to the reader as an exercise, with extra points to be
awarded for sufficiently clever explanations as to why they chose
to put a given sort of part into a given bin....:-)
Bob M.
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Author: Jonathan KirwanDate: 21:28 02-08-07
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On Thu, 02 Aug 2007 16:24:25 -0700, David Harmon <source@netcom.com>
wrote:
>What exactly is the definition of an "active" device? I think of it as
>"capable of being used in some way to provide amplification" but that
>seems horribly imprecise,
I think this is a good question because it made me thing a little more
about the idea.
Basically, I used to look at an active device or function block as one
that requires attachment to a power source in order to properly
operate.
In contrast, a passive device or function block is one where it can
perform its service without access to a separate power source.
So a passive block looks like:
,---------,
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signal in -----> | | -----> signal out
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'---------'
and an active block looks like:
pwr
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,---------,
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signal in -----> | | -----> signal out
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'---------'
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gnd
A transistor is active because it cannot perform most of its usual
actions (control action, voltage or current amplification, or power
gain) without access to a power source. A resistor is passive because
it usually doesn't require the supply of power to perform its action.
However, none of that is perfect.
Is a diode active or passive under these definitions?
Jon
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Author: Bob MyersDate: 22:22 02-08-07
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"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in message
news:7uv4b391sa63iof2jpan1d86gvlr503ui7@4ax.com...
> However, none of that is perfect.
>
> Is a diode active or passive under these definitions?
Under this definition, it's passive, as it requires no external
power source. That was the same problem I had with that
definition.
Or, just to throw more JP-4 onto the fire..:-) - what's a
solar cell? A photodiode?
Bob M.
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Author: JeffMDate: 23:09 02-08-07
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JeffM wrote:
>>Trying to define it so that a relay is excluded[1]
>>but semiconductors used in digital mode aren't is kinda tough.
>> [1] or does someone consider a relay an active device?
>>
Bob Myers wrote:
>I think I'd have to consider a relay "active"
>in a broad enough sense of that term
>
REALLY broad, IMO.
> - and I'm also having problems narrowing it down
>such that it doesn't exclude some other things
>that ARE commonly thought of as "active."
>
Yup. Kirwan mentioned diodes.
>I'm trying to think of the right terminology to cover transformers
>
...and when considering wound components,
*saturable reactors* are a fly in the ointment.
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Author: Michael BlackDate: 23:27 02-08-07
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JeffM (jeffm_@email.com) writes:
> JeffM wrote:
>>>Trying to define it so that a relay is excluded[1]
>>>but semiconductors used in digital mode aren't is kinda tough.
>>> [1] or does someone consider a relay an active device?
>>>
> Bob Myers wrote:
>>I think I'd have to consider a relay "active"
>>in a broad enough sense of that term
>>
> REALLY broad, IMO.
>
But really, all that's needed is a broad definition, and
then add that there are expections.
The poster is trying to wrap his head around the concept, not
fully define the term.
Start with why there is a defining line, either it serves
a purpose or there was no good reason for drawing that line.
Once one understands why there is a need to divide between
active and passive, then the definition becomes more obvious.
Transistors, capacitors and relays (or no relays) are merely
examples of active and passive devices. They don't define
the terms.
So once someone figures out a basic definition, that should
suffice, avoiding the examples completely, or more likel
using the examples to reinforce the definition, rather defining
with the examples.
SO long as you use examples to define, there will always be
exceptions, and likely even some devices that can fall into
either camp, depending on useage.
Michael
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Author: EeyoreDate: 23:35 02-08-07
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Jonathan Kirwan wrote:
> Is a diode active or passive under these definitions?
A diode is a non-linear resistor and it requires no 'external' power to
function. So passive.
Graham
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Author: EeyoreDate: 23:36 02-08-07
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JeffM wrote:
> David Harmon wrote:
> >What exactly is the definition of an "active" device? I think of it
as
> >"capable of being used in some way to provide amplification"
> >but that seems horribly imprecise
>
> Trying to define it so that a relay is excluded[1]
> but semiconductors used in digital mode aren't is kinda tough.
> The definition offered by "Nobody"
> http://www.google.com/search?q=define:active+device ??
> doesn't do a good job at that.
> .
> .
> [1] or does someone consider a relay an active device?
> Konrad Zuse perhaps?
A relay can provide power amplification. That certainly rules it out as passive
in my book.
Graham
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Author: JeffMDate: 00:22 03-08-07
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JeffM wrote:
>>>>Trying to define it so that a relay is excluded[1]
>>>>but semiconductors used in digital mode aren't is kinda tough.
>>>>[1] or does someone consider a relay an active device?
>>>>
Bob Myers wrote:
>>>I think I'd have to consider a relay "active"
>>>in a broad enough sense of that term
>>>
JeffM wrote:
>>REALLY broad, IMO.
>>
Michael Black wrote:
>But really, all that's needed is a broad definition, and
>then add that there are expections.
>
>The poster is trying to wrap his head around the concept, not
>fully define the term.
>
>Start with why there is a defining line, either it serves
>a purpose or there was no good reason for drawing that line.
>Once one understands why there is a need to divide between
>active and passive, then the definition becomes more obvious.
>
>Transistors, capacitors and relays (or no relays) are merely
>examples of active and passive devices. They don't define
>the terms.
>
>So once someone figures out a basic definition, that should
>suffice, avoiding the examples completely, or more likel
>using the examples to reinforce the definition, rather defining
>with the examples.
>
>SO long as you use examples to define, there will always be
>exceptions, and likely even some devices that can fall into
>either camp, depending on useage.
Well, now you're just making it too easy. 8-)
An active device controls an output voltage or current
by means of an input voltage or current
or it has an intrinsic turn-on threshold or non-linear curve.
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Author: David HarmonDate: 00:57 03-08-07
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On Fri, 03 Aug 2007 04:35:44 +0100 in sci.electronics.basics, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote,
>
>Jonathan Kirwan wrote:
>> Is a diode active or passive under these definitions?
>
>A diode is a non-linear resistor and it requires no 'external' power to
>function. So passive.
How about a tunnel diode?
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Author: Phil AllisonDate: 01:01 03-08-07
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"David Harmon"
>
> What exactly is the definition of an "active" device?
** The short answer is - there isn't one.
The term " active " is a name used to classify strictly electronic devices
as opposed to merely electrical devices and is defined by popular usage,
not science.
It includes all semiconductors, valves ( or tubes) and maybe even the humble
neon lamp.
Electromechanical devices, like relays, are not included because they are
electrical rather than electronic.
...... Phil
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Author: Michael BlackDate: 01:04 03-08-07
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David Harmon (source@netcom.com) writes:
> On Fri, 03 Aug 2007 04:35:44 +0100 in sci.electronics.basics, Eeyore
> <rabbitsfriendsandrelations@hotmail.com> wrote,
>>
>>Jonathan Kirwan wrote:
>>> Is a diode active or passive under these definitions?
>>
>>A diode is a non-linear resistor and it requires no 'external' power to
>>function. So passive.
>
> How about a tunnel diode?
>
That's the example I was thinking of that can be both passive
and active, depending on useage.
Michael
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Author: Dr. PolemicDate: 02:14 03-08-07
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On Fri, 3 Aug 2007 15:01:07 +1000, "Phil Allison" <philallison@tpg.com.au>
wrote:
>
>"David Harmon"
>
>>
>> What exactly is the definition of an "active" device?
>
>
>** The short answer is - there isn't one.
>
>The term " active " is a name used to classify strictly electronic devices
>as opposed to merely electrical devices and is defined by popular usage,
>not science.
>
>It includes all semiconductors,
Eeyore disagrees with you on this. I think you should insult him.
>valves ( or tubes) and maybe even the humble
>neon lamp.
>
>Electromechanical devices, like relays, are not included because they are
>electrical rather than electronic.
>
>
>
>
>...... Phil
>
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Author: Rich GriseDate: 15:52 03-08-07
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On Thu, 02 Aug 2007 17:56:38 -0700, JeffM wrote:
> .
> [1] or does someone consider a relay an active device?
> Konrad Zuse perhaps?
Only if he wants to start a religious war. ;-)
Cheers!
Rich
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Author: Rich GriseDate: 16:03 03-08-07
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On Fri, 03 Aug 2007 03:27:27 +0000, Michael Black wrote:
> either camp, depending on useage.
> ^^^^^^
Usage.
But, notwithstanding that, the one device that to me perfectly
straddles the active/passive line is the diode.
Stick a diode in the feedback loop of a voltage follower, and
you have a "precision rectifier". Is the diode "active" or
"passive" in this role? >:->
Cheers!
Rich
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Author: Rich GriseDate: 16:05 03-08-07
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On Thu, 02 Aug 2007 21:22:40 -0700, JeffM wrote:
...
> or it has an intrinsic turn-on threshold or non-linear curve.
Boy, that would simplify things!
Active == Non-linear.
;-)
Cheers!
Rich
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Author: Rich GriseDate: 16:09 03-08-07
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On Fri, 03 Aug 2007 04:36:51 +0100, Eeyore wrote:
> JeffM wrote:
>> David Harmon wrote:
>> >What exactly is the definition of an "active" device? I think of
it as
>> >"capable of being used in some way to provide amplification"
>> >but that seems horribly imprecise
>>
>> Trying to define it so that a relay is excluded[1]
>> but semiconductors used in digital mode aren't is kinda tough.
>> The definition offered by "Nobody"
>> http://www.google.com/search?q=define:active+device ??
>> doesn't do a good job at that.
>> .
>> [1] or does someone consider a relay an active device?
>> Konrad Zuse perhaps?
>
> A relay can provide power amplification. That certainly rules it out as passive
> in my book.
Gaw, we could drag this on for months! Is a solenoid active? Is a switch
active? Switches certainly do get "activated", or maybe "actuated"
would
be more accurate. ;-)
But, when you control a switch with a solenoid (i.e., "relay"), I believe
it suddenly becomes an active device.
Then again, I've seen solenoids that certainly do some activity! Ever
played pinball? ;-)
Cheers!
Rich
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Author: Rich GriseDate: 16:19 03-08-07
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On Fri, 03 Aug 2007 05:04:04 +0000, Michael Black wrote:
> David Harmon (source@netcom.com) writes:
>> On Fri, 03 Aug 2007 04:35:44 +0100 in sci.electronics.basics, Eeyore
>>>Jonathan Kirwan wrote:
>>>> Is a diode active or passive under these definitions?
>>>
>>>A diode is a non-linear resistor and it requires no 'external' power to
>>>function. So passive.
>>
>> How about a tunnel diode?
>>
> That's the example I was thinking of that can be both passive
> and active, depending on useage.
^^^^^^
USAGE!
Misspellings like this really impugn your credibility.
Thanks,
Rich
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