Diodes

[tweaked]

I have done a bunch of searches but can't find answers to these questions about diodes where it's spelled out simply and clearly...

1. do different diodes have different values (do diodes even have values?)
2. can you use any type of diode when it calls for a diode in a circuit? Can you use an LED any time it calls for a diode?
3. is there a difference in different led's besides the physical dimensions (gets back to question 1)? If there's a difference, how do you know what it is since there are no markings, and what do you have to do to the circuit in order to use the different types?


***also another quick question which is about resistors.... if the circuit calls for a resistor and the value just says 47 or 560 with no "uF" or "mF" after the number... what does that mean? is the "uF" assumed in those cases?

[Seljer]

1. Yep, they have a bunch of various attributes, google the model # of the diode and look over data sheets

among the most common things are:
-forward voltage (how much voltage is needed to 'open' current flow through the diode, for silicon diodes 0.6V, for germanium 0.3V, for leds anything from 1.5V to 5V depending on color)
-breakdown voltage (how much voltage you can apply to the diode in the wrong direction before it goes 'poof')
-reverse leakage (because diodes aren't perfect they still let a couple of nA through in the wrong direction)
-power/current ratings

there are a bunch of different types of diodes common are silicon diodes (the 1n400X series, generally these are power diodes for use in rectifiers), gold-doped silicon diodes (these are faster at responding to signals, lthe 1n914 and 1n4148), zener diodes (they have a specific breakdown voltage while working like a normal diode when used normally)

2. Nope. Different situations call for different power ratings and forward voltages.

3. Different colors have different forward voltages (blue and white leds need need more voltage to turn on than red ones for example), as well as having different magnitudes of brightness at the same current.

[markm]

Check here,
This may help you.

http://ourworld.compuserve.com/homepages/G_knott/index8.htm

[tweaked]

thanks - reading it now!

[tweaked]

1. Yep, they have a bunch of various attributes, google the model # of the diode and look over data sheets

among the most common things are:
-forward voltage (how much voltage is needed to 'open' current flow through the diode, for silicon diodes 0.6V, for germanium 0.3V, for leds anything from 1.5V to 5V depending on color)
-breakdown voltage (how much voltage you can apply to the diode in the wrong direction before it goes 'poof')
-reverse leakage (because diodes aren't perfect they still let a couple of nA through in the wrong direction)
-power/current ratings

there are a bunch of different types of diodes common are silicon diodes (the 1n400X series, generally these are power diodes for use in rectifiers), gold-doped silicon diodes (these are faster at responding to signals, lthe 1n914 and 1n4148), zener diodes (they have a specific breakdown voltage while working like a normal diode when used normally)

2. Nope. Different situations call for different power ratings and forward voltages.

3. Different colors have different forward voltages (blue and white leds need need more voltage to turn on than red ones for example), as well as having different magnitudes of brightness at the same current.

Perfect - thank you!

[Seljer]

"***also another quick question which is about resistors.... if the circuit calls for a resistor and the value just says 47 or 560 with no "uF" or "mF" after the number... what does that mean? is the "uF" assumed in those cases?"

resistors are measured in ohms (also writtena as "Ω"), not farads ("F"). In those cases it means just 47 ohms or 560 ohms (as opposed to larger kiloohms or megaohms)

[tweaked]

"***also another quick question which is about resistors.... if the circuit calls for a resistor and the value just says 47 or 560 with no "uF" or "mF" after the number... what does that mean? is the "uF" assumed in those cases?"

resistors are measured in ohms (also writtena as "Ω"), not farads ("F"). In those cases it means just 47 ohms or 560 ohms (as opposed to larger kiloohms or megaohms)

I have the feeling this will be good to know ;-)

Thanks!