DIYbanter - View Single Post - Anyone help me with component ID for X5DIJ-SX039C laptop (k501j mobo)?

Kaz Kylheku

On 2014-01-29, wrote:
"A diode is not active by itself, because it's a two-port circuit. There is no
way for it to have an input which controls an output. "

So your contention then is that tunnel diodes, Gunn diodes and Zener diodes
are not active devices.

I'm trying to classify them as such, but I am unable to think of the
justification.

If that is so, then a magnetron is also passive. It is technically a diode
with an indirectly heated cathode unless you consider the magnet an element.
Also, what of the case of a Hall effct device ? Nothing electronic controls
it, only a magnetic field. Other devices can have more than two terminals
aqnd be passive, so where does the Hall effect fit in there ?

These devices can be active if we broaden the definition of "input", and
"energy" and so on beyond electronics. I already gave an example of automobile
power steering being active.

In the case of semiconductor diodes, we have photodiodes. (Actually any
silicon diode reacts to light, just isn't necessarily packaged for that use.)
The two ports of a photodiode can be configured to pass current from a power
supply. The light falling on the junction can be regarded as an input: a third
port which modulates the current. This is then "active": some energy delivery
is modulated in proportion to the light, and yet most of the energy is not
derived from that light.

Hall effect sensors and such can be conceived similarly.