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Mimimum base current for 2N3055

Discussion in 'Electronic Design' started by [email protected], Feb 15, 2013.

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  1. Guest

    Could some electronics guru please help ?
    What is the minimum base current for the
    2N3055 ? The On Semi data sheet that I
    downloaded is not very helpful. Thanks in
    advance for your help.
     
  2. Phil Allison

    Phil Allison Guest


    ** You Q makes no sense.

    Some context is ESSENTIAL !!



    ..... Phil
     
  3. Minimum base current? You can probably feed it 10nA and get ~1uA from
    the collector... but that would be a pretty silly thing to do.

    If you're looking at the same data sheet I down loaded then figure 2
    shows typical current gain vs collecter current. (divide Ic by hfe
    and you have an estimate of the base current you'll need.) Unless you
    want to saturate the thing... then figure 3 is your friend.

    As Phil and JF said, more context is needed if you want more specific
    advice.

    George H.
     
  4. Tim Williams

    Tim Williams Guest

    Or if you mean direction, not just magnitude, then you can probably sink
    five or ten amperes out of it ("IB2 = -5A" or whatever), during reverse
    recovery of the B-E junction. It'll only last a couple microseconds
    though.

    Tim
     
  5. You could feed it a negative current too.. minimum current to damage
    the E-B junction? Minimum current to burn off the bonding wire?
     
  6. Yes I was torn between "zero" and some negative damage threshold.

    I thought I saw something about 2N3055 being good for a low noise
    amplifier, which sounds ridiculous but could be related...

    [...]
     
  7. whit3rd

    whit3rd Guest

    It's not a switching device, so the current into the base
    has a 'minimum' only in the sense that a hot device under
    bias leaks from the collector. So, to reliably turn OFF the
    transistor, you might need to sink 200 mA/beta
    at 25 C, 60Vce (that's circa 2 mA).

    The specs on beta (also known as h_fe) are, of course,
    very loose; 20 to 70 at 4A, and there's temperature
    and collector-current variations in the charts.

    My source here is the RCA file #145, dated August 1966
    (that's the most complete data sheet I know of for this part).
     
  8. Robert Baer

    Robert Baer Guest

    Zero.
     
  9. Guest


    Finally someone who can actually understand the question.
     
  10. Guest

    I did that on a physics exam in college. The question didn't
    eliminate the trivial answer. The prof thought I was being a smartass
    and I thought he was throwing out one of his famous trick questions.
    It did seem a little odd that zero being the answer to that question
    made the next quarter of the exam result in zero answers, also (a bit
    much for a trick question but it was correct). He was a bit miffed
    but gave me credit on the exam. It was a correct answer.
     
  11. Jamie

    Jamie Guest

    I think you're talking about the Beta(Hfe) curve..
    should be a chart in the spec showing at what point the
    transfer is at the max.

    That's an old part and many published data sheets.

    Some one told me once that a 3055 was just a ball
    park component, soured from various other high power
    transistors that may have not met their mark. If that
    being the case, it's possible you may find large noticeable
    differences from lot to lot.


    Jamie
     
  12. Phil Allison

    Phil Allison Guest

    "George Herold"
    Minimum base current? You can probably feed it 10nA and get ~1uA from
    the collector

    ** That is VERY unlikely - the Hfe of power BJTs falls at low ( and high)
    currents so much so that most data sheets do not spec it below about 50mA
    Ic.

    Long time ago, I was checking the Hfe of a batch of Motorola MJ4502s - I
    came across one that tested 450 at 1mA Ic.

    I thought of framing it....


    ..... Phil
     
  13. Well OK, I've been using these TIP31/32 's in to220 pacs as temp
    sensors,
    diode conected transitors. At 10nA of collector current the ideality
    is starting to fall off, 100nA looks OK. I figured a higher power BJT
    might be 'good' to 1uA.

    Have you measured a 3055 at 1uA?
    (I did say probably..)

    George H.
     
  14. Phil Allison

    Phil Allison Guest

    "George Herold"
    "Phil Allison"
    Well OK, I've been using these TIP31/32 's in to220 pacs as temp
    sensors, diode conected transitors. At 10nA of collector current the
    ideality is starting to fall off, 100nA looks OK. I figured a higher
    power BJT might be 'good' to 1uA.


    ** So you just fucking guessed.

    How typical for this NG.

    ** Hundreds of them.


    FYI:

    I just tested a vintage 1983 MJ802.

    With 1uA base current, Ic = 4uA

    With 100uA base current , Ic = 1.8 mA

    With 4.5mA base current, Ic = 0.6 A



    ..... Phil
     
  15. Guest

    According to urban legends, some manufacturers even branded failed VHF
    transmitter transistors as 2N3055 and caused huge stability problems
    in existing circuits :)

    So if the original specification called for fT > 0.8 MHz, so it would
    be OK to sell a transistor with fT > 500 MHz as long as the other
    requirements were met.
     
  16. legg

    legg Guest

    That's Icbo to all you sports fans out there.

    RL
     
  17. Guest

    Thanks. As one of the other posters have noted,
    the specifications are pretty loose, in that
    most (like the one from On Semi) state that
    hfe varies between 20 - 70, and at hfe of 70,
    the collector current is 4.0 A, which is not
    very helpful. What you have said, is however
    a lot more concrete.
     
  18. Guest

    I fully agree.
     
  19. Phil Allison

    Phil Allison Guest

    ** You are fully a fuckwit and a troll.

    Learn to write English properly or else **** OFF !!!!



    ..... Phil
     
  20. Phil Allison

    Phil Allison Guest


    ** OK so you CANNOT read English either.

    You are quite wrong and you have no comprehension of the topic.

    **** off.


    ...... Phil
     
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