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Is there a "classic" diode?

Discussion in 'Electronic Basics' started by Michael, Dec 28, 2003.

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  1. Michael

    Michael Guest

    Is there a "classic" diode? One that is designed to do only what diodes are
    famous for - only allow current to flow in one direction? I'm guessing that
    it's the 1N4001 - because that's the diode I see used the most. But I could
    also be completely off. What do you think? Thanks!

  2. Make it a 1N4004 and you are pretty close.
  3. Michael

    Michael Guest

    I looked up the datasheet for the 4004 - and then I realized that it was
    the same datasheet as the 4001!
    ( So essentially 1N4001-
    1N4007 are the same diodes - just with increasing Peak Repetitive Reverse
    Voltages (which is something I'm not even familiar with - though using
    common sense I have a good idea) So is there any reason that one couldn't
    be substituted for the other in a design as long as you weren't expecting
    the diode to encounter large Peak Repetitive Reverse Voltages? Also - does
    this kind of diode come in a package with 18awg leads? I can't stand thick

  4. CFoley1064

    CFoley1064 Guest

    Is there a "classic" diode? One that is designed to do only what diodes are

    The "desert island" question for diodes. Hmmn....

    1N400X -- Obvious choice for a first power rectifier diode. Good for 1 amp,
    PRV dependent on X (get 1N4007 if you only want to stock one, because its PRV
    is 1000V, and you can always substitute a 1N4007 for any of the others.
    Inexpensive due to popularity.

    1N914B/1N4148 -- These diodes sub for each other, as well as 1N914 and 1N914A.
    One of the problems with the 1N400X is that it has a large diifuse die area and
    high junction capacitance, and as a result isn't very good at high speed
    rectification (anything over about 1KHz). When voltage across the diode
    switches, the junction capacitance has to charge up before it blocks current,
    and this charge passes through the diode. The 1N4148 is made with a smaller,
    much better defined P-N junction, and so has less junction capacitance, and
    works well at higher speed. It doesn't have as high a voltage or current
    rating (75V @ 150 mA), but is very useful to have. This diode is also called a
    "switching diode" or "computer diode". Again, inexpensive due to large volume.

    The above would be the first two I'd get a hundred of just to have around in
    the parts bin. After that, it kind of depends on where you want to go. The
    above diodes are standard silicon. You have germanium and schottky diodes too,
    as well as a wide range of currents/speeds/leakage current requirements.
    That's why there are so many different kinds.

    Good luck.
  5. The "Thick leads" are there to conduct heat away from the diode so it
    doesn't overheat and fail. Buy a small pair of needle nose pliers to
    shape the leads the way you want them.
    Merry Christmas!

    Take care, and God bless.
    Michael A. Terrell
    Central Florida
  6. ---------------------
    If you mean sort of like the 2N2222A/2N2907 and 2N3904/2N3906 are for
    transistors, then yes. The "classic" small signal logic diode is the
    1N914/1N4148, and the classic power diode is the 1N400x family, where
    the x signifies ranges of breakdown PIV.

  7. cpemma

    cpemma Guest

    Also - does this kind of diode come in a package
    The 1N4000S series come with 0.6mm leads (1N4000 are 0.8mm), mainly aimed at
    auto-insert equipment, but they're the same price in small quantities. Rapid
    do them in the UK
  8. volume.

    Actually the junction capacitance isn't usually the reason why the 1N400X
    series devices aren't appropriate for high frequency use. The 1N400X
    devices are known as standard recovery rectifers. That is, their reverse
    recovery time is quite long somewhere in the low microseconds range.
    Reverse recovery currents are a different phenomena than the junction
    capacitance displacement current, although they often both occur at about
    the same time during a switching event and therefore are difficult to
    separately distinguish.

    If current is flowing in the forward direction through the diode at the
    moment just before the diode becomes reverse biased, the diode will not
    instantly start blocking the voltage/current. Instead a large transient may
    occur momentarily until the diode can start blocking properly. The energy
    contained in this transient is generally much larger than the energy that is
    contained in the diode's junction capacitance, however the exact value is
    not fixed, but depends on a number of factors such as die temperature, dI/dt
    of the switching event, and the current that was flowing just prior to
    polarity reversal. If forward current is not flowing through the diode
    several microseconds prior to polarity reversal there will be no reverse
    recovery transient.

    The duration of this reverse recovery time can be reduced by deliberately
    introducing impurity metals such as gold and platinum into the crystal which
    introduces intermediate energy levels between the valence and conduction
    bands. These extra energy levels serve as centers for recombination.
    Diodes such as fast recovery, and ultra fast recovery use this type of
    method to improve their switching performance.
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