active devices and passive devices

[James Hanley]

i'm looking at the definition for active device


"active device: A device that requires a source of energy for its
operation and has an output that is a function of present and past
input signals. Note: Examples of active devices include controlled
power supplies, transistors, LEDs, amplifiers, and transmitters."

what active device has a power source but its output is not a function
of its input signals?
Also. An LED doesn't even have input signals does it???!!! I can't
see why it fits into that definition of active device.

thanks

 

[aman]

An active device is any type of circuit component with the ability to
electrically control electron flow (electricity controlling
electricity). In order for a circuit to be properly called electronic,
it must contain at least one active device. Components incapable of
controlling current by means of another electrical signal are called
passive devices. Resistors, capacitors, inductors, transformers, and
even diodes are all considered passive devices. Active devices include,
but are not limited to, vacuum tubes, transistors, silicon-controlled
rectifiers (SCRs), and TRIACs.

Hope this helps.

James Hanley wrote:

i'm looking at the definition for active device


"active device: A device that requires a source of energy for its
operation and has an output that is a function of present and past
input signals. Note: Examples of active devices include controlled
power supplies, transistors, LEDs, amplifiers, and transmitters."

what active device has a power source but its output is not a
function
of its input signals?
Also. An LED doesn't even have input signals does it???!!! I can't
see why it fits into that definition of active device.

thanks

 

[Kitchen Man]

On 2 Mar 2005 10:58:24 -0800 in sci.electronics.basics,
jameshanley39@yahoo.co.uk (James Hanley) wrote msg
<930a4bf.0503021058.5d8031e5@posting.google.com>:

i'm looking at the definition for active device

"active device: A device that requires a source of energy for its
operation and has an output that is a function of present and past
input signals. Note: Examples of active devices include controlled
power supplies, transistors, LEDs, amplifiers, and transmitters."

what active device has a power source but its output is not a function
of its input signals?
Also. An LED doesn't even have input signals does it???!!! I can't
see why it fits into that definition of active device.

You've stumbled into an ongoing debate. I agree (as I think most in the
industry do) with "aman"'s description, but you'll find other sources
that will group diodes as active devices. Don't worry too much about
it.

--
Al Brennan