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difference between bipolar and mosfet

Discussion in 'Electronic Basics' started by Skeleton Man, Jan 8, 2005.

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  1. John Fields

    John Fields Guest

    Apology accepted.
  2. John Fields

    John Fields Guest

    Hardly. Your statement:

    "Sadly, pointing out the truth about certain things in this world is
    no longer acceptable. Political-correctness and such like. It's slowly
    getting worse, too. For some factual historical views one can even
    risk imprisonment and have one's carreer and livelihood destroyed. The
    views are too important to hide, so they have to be disseminated by
    stealth. It requires that certain precautions be taken. A shameful
    situation, I grant you."

    contains no mention of the method of anonymity you use, hiding, which
    you admit to later on in the post to which I'm currently replying.

    Consequently, it's not a question of lack of comprehension on my part,
    but a lack of clarity on yours.

    However, I should have guessed that would be your method of choice
    judging from the bob-and-weave tactics you've employed in your earlier
    If you have to hide to preserve your liberty then you have no liberty
    to preserve.
    More bob-and-weave, huh?

    The point wasn't that the change in drop was a large percentage of the
    drop at the knee, it was that the change in drop was small compared to
    the large change in current through the diode. If you recall, the
    application was inserting a silicon diode or two in series with a
    power supply in order to realize the ~ 0.7V drop each diode would
    yield with the device operating, to which you responded with:

    "Um, yeah, but they drop voltage _according_ to current! If they're
    dropping 0,7V., they're not passing much current! Diodes are a crap
    way to drop voltage unless the load is light and predictable!!!"

    which _is_ crap since, in the first place, the load current will be
    predictable since it will vary between two limits and, in the second
    place, the drop across the diode with the variations in load current
    and junction temperature will also be predictable.

    For example, a 1N5400 will drop about 0.7V with about 100mA through
    the junction, but that drop will only increase by 200mV for an
    increase in current to 3A.

    Likewise, a 1N3491 will drop about 0.7V with 100mA through the
    junction, but with 0.9V across the junction the current through the
    diode will be about 8 amps.

    So, in the first case, if a 200mV change in input voltage to a load
    can be tolerated for a load current change of 3 amps, it'll work fine.

    In the second case, an 8 amp change in load current will cause a
    change of only 200 mV in the drop across the diode. Not exactly what
    I'd call a 'light' load, and all of it predictable.
    Well, IME, for the same If, Vf depends on what the diode's made of.

    Easy enough to check it out... get yourself a 9V battery, a 20K
    rheostat, a silicon junction diode, a Schottky diode, a 0-1mA ammeter
    and a 0-1V voltmeter. Making sure you have the rheostat cranked to
    the max resistance position, connect everything up like this:

    |A |
    [DUT] [0->1V]
    | |

    Then, adjust the rheostat to the position required to make the
    milliammeter read 1mA, note whether the DUT is the Schottky or not and
    write that down along with the voltage indicated by the voltmeter when
    the milliammeter reads 1mA. Do the same thing using the remaining
    diode and report back to us with what you find, OK?
    Before you can determine whether or not someone knows how a BJT works,
    you need to know how a diode works. You haven't demonstrated any real
    competence in that arena, so I suggest you do the experiment I
    described and see what you can learn from it.
  3. John Fields

    John Fields Guest

  4. Jamie

    Jamie Guest

    i don't remember ever getting involved in this thread, i was just
    enjoying the bickering that was taking place.
    i don't need to open text books on Silicone theory, let see if i can
    remember anything from years ago. 4 electrons for each (silicone)which
    bond to 4 other atoms, N Dope material that has 5 electrons which allows
    one to move freely and the P material that has 3 electrons which creates
    a hole, or more like a void etc..(poorly worded i know)
    i don't remember the compounds used now for the N an P doping/but
    phosphorus, arsenic, boron,gallium and some others i can't remember.
    all i remember is that they need > 4 electrons for the N dope
    and < 4 for the P dope.
    the above maybe a little vague because i don't sit and study physics and
    have no need to keep that at the top of my head every day.
    SO what ever, transistor theory is basic to me , i understand and
    know how to work with it and i guess that is all that matters.
    Have a good day.
  5. Jamie

    Jamie Guest

    how's it going John.. see your having a nice day :))
    keep up the good work.!
  6. Bob Myers

    Bob Myers Guest

    Ummmm...I would like to point out that the "relative" in most
    relevant cases here will mean "with respect to other DC voltages
    in the circuit," NOT with respect to the magnitude of the B-E
    drop itself. For the purpose of most DC biasing calculations,
    f'rinstance, assuming the B-E junction to be a constant drop of
    ~0.6-0.7V works just fine, thank you very much. You can go
    back and refine things if you like, later on, but you'll generally wind
    up with results far closer to reality than the accuracy you can
    count on in the component values, supply voltage, etc.. So
    what's all the hubbub, bub?

    Why do I get the impression that the "works and plays well
    with others" box was rarely checked on your report card? :)

    Bob M.
  7. Miles Harris

    Miles Harris Guest

    On Fri, 14 Jan 2005 10:58:06 -0600, John Fields

    [semantics snipped]
    More semantics.. Where's the beef??
    Semantics again...

    [snip more bilge]
    No really??? Goodness me!
    I don't have to do this stupid experiment. Any half-competent engineer
    will know that the barrier height potential of the Schottky will be
    *much* lower than a 'comparable' silicon diode. You're talking maybe
    270mV. Germaniums likewise (but you won't remember germanium diodes,
    Junior). Shall we perform your dumb experiment with other types, too?
    How about a back diode? can you get any lower than that?
    If I learned anything new from *that* experiment I'd give up
    electronics altogether tomorrow.
    There's nothing wrong with my diode theory, Junior. I'd probably
    completed my studies before you were even born. Don't talk back to
    your elders and betters. Learn some respect.

    Sorry, no compliment intended. I infer you're older in view of your
    cockiness and the foul language you readily resort to each time your
    ignorance is exposed.
    HAND, Junior!
  8. Miles Harris

    Miles Harris Guest

    I don't know. Ask Fields. He's the one with the problem!
    I'm well aware that diodes are used to drop voltage in many circuits.
    The technique crops up frequently in the drives to Class AB and B
    amplifiers. It has shortcomings, however and I'd never suggest a
    newbie make use of it.
    Correct. No one likes an achiever, but I never gave a damn about
    popularity. My coursework always came first - like myself at the top
    of the class.
  9. John Fields

    John Fields Guest

    Now that I've explained it to you you can pretend you knew it all

    Here's a little something (Positively Fourth Street) from Bob Dylan
    you might identify with: (Pay particular attention to the sixth,
    eleventh, and twelfth verses.)

    You got a lotta nerve
    To say you are my friend
    When I was down
    You just stood there grinning

    You got a lotta nerve
    To say you got a helping hand to lend
    You just want to be on
    The side that's winning

    You say I let you down
    You know it's not like that
    If you're so hurt
    Why then don't you show it

    You say you lost your faith
    But that's not where it's at
    You had no faith to lose
    And you know it

    I know the reason
    That you talk behind my back
    I used to be among the crowd
    You're in with

    Do you take me for such a fool
    To think I'd make contact
    With the one who tries to hide
    What he don't know to begin with

    You see me on the street
    You always act surprised
    You say, "How are you?" "Good luck"
    But you don't mean it

    When you know as well as me
    You'd rather see me paralyzed
    Why don't you just come out once
    And scream it

    No, I do not feel that good
    When I see the heartbreaks you embrace
    If I was a master thief
    Perhaps I'd rob them

    And now I know you're dissatisfied
    With your position and your place
    Don't you understand
    It's not my problem

    I wish that for just one time
    You could stand inside my shoes
    And just for that one moment
    I could be you

    Yes, I wish that for just one time
    You could stand inside my shoes
    You'd know what a drag it is
    To see you

    Bob Dylan
    And yet, "knowing" all that you chose to make this unqualified
    statement earlier on?:

    "You *do* realize that one diode drop at room temperature is only just
    over half a volt, don't you, Junior?"

    I'd say that sentence speaks volumes about your competence.
    Sure I do. they were after copper oxide and selenium, but before
    An experiment can't be dumb, [stupid] but the experimenter can.
    That's why I suggested that _you_ start with the pot cranked to
    maximum resistance.
    I'd have to look it up to find out, but the subject isn't diodes with
    a negative resistance characteristic, it's just plain ol' garden
    variety rectifiers.
    Hmmm... Where have I heard _this_ before?:

    "You *do* realize that one diode drop at room temperature is only just
    over half a volt, don't you, Junior? "
  10. Miles Harris

    Miles Harris Guest

    I ain't pretendin' nuthin'. This is all *basic* stuff and nowhere near
    even undergrad level.
    None of which is applicable here. Thank God they don't write 'em like
    that anymore.
    I'd say your remark simply shows once again that you either don't
    read, or don't understand, what is written for your consumption. (That
    much was obvious from your tedious exchanges with Kevin). You ought to
    know perfectly well that my earlier comments were in relation to a
    typical silicon diode with a Vbe of 0.6-0.7V. Allow me to quote from
    an earlier post of mine made 2 days ago:

    "Really? So what is it you're taking issue with? Taken as a
    generalization for most silicon diodes I can't see real problem with

    I thereby made it perfectly clear I was *not* including the more
    exotic varieties of diode in my remarks!

    So you did a little research on the Web, uh, Junior? Well it's about
    time you absorbed something for a change. Keep it up!
    How very thoughtful. And there was I about to connect it straight
    across a lead/acid battery...(forward-biased, of course).

    Indeed. So why all this nonsense about Schottkys?
    Your ignorance is only exceeded by your persistence, I'll grant you

    Fine; that's the way it is all too often with you kids today. I blame
    rap music for turning their heads.
    ROTFLMAO!! That's rich, coming from you of all people.
    "FOAD" isn't a swear word; it's an acronym containing one. I wouldn't
    stoop so low as post the 'F-word' in a public forum. And from what
    I've read of Mr. Thompson's contributions, he makes pretty frequent
    use of the acronym himself. "Honi Soi Qui Mal Y Pense" as they say in
  11. John Fields

    John Fields Guest

    What a surprise!
    Don't undestand allusion, huh?
    A 9V lead-acid battery? Where would you propose to find one of those?
    Nonsense? Schottkys _are_ as plain ol' garden variety diodes as
    silicon junction diodes are WRT negative resistance characteristics,
    but that's hardly the point, the point being that you made the
    statement (no matter how you hard you try to slime out of it) that a
    diode's Vf is about 0.5V at room temp, which it is _not_ if you're
    talking about a silicon junction diode, which we were.

    Fine; that's the way it is all too often with you kids today. I blame
    rap music for turning their heads.[/QUOTE]

    Did you really think the lyrics I posted earlier were from a rap song?

    I blame phony, self-important bastards like you who drive them to want
    to do _anything_ but be like you. Watch that eleven-year-old...
    IKYABWAI? Pretty lame, Bozo!
    But you'd stoop even lower by refusing to?

    An interesting picture of you is emerging from this exchange;
    basically that of someone who is afraid to say what he really means or
    with being associated with having said it. Basically, a coward.
  12. Miles Harris

    Miles Harris Guest

    I understand allusion perfectly, Junior. What I don't understand is
    why some spotty-faced, high-school-reject jerkoff like you would want
    to post lyrics from a song that so clearly flags up his own
    self-loathing. You're so full of yourself in your postings, yet you
    cite self-disparaging lyrics that basically show you up to be the sad,
    sorry-assed, sack of s**t loser/loner that you really are. That's
    quite an admission in a world-wide public forum!
    I appreciate you're only trolling here, Junior, but if you do a little
    research on the Web you'll find that such batteries are comprised of a
    series of lower value cells. You just place them in series and stick
    'em in one box and voila: you have the required voltage.
    BTW, I don't appreciate sarchasm from spotty-faced, high school
    rejects, so cut the crap and show some respect, boner.
    You can't have it both ways, Junior. Let me repost that quote of mine
    that you're so fond of citing in this thread:

    Now, please tell us which common-or-garden, run-of-the-mill,
    general-purpose silicon diode *doesn't* have a drop of "just over half
    a volt" at room temperature??

    Yes, I do. As is clear for all to see. Sadly, I don't have Kevin
    Aylward's degree of persistence, however.
    I find it exceedingly tiresome to have to repeat, ad nauseam, the kind
    of entry-level basics that my youngest son was acquainted with a good
    3 years ago.
    Certainly not. I know the song you quoted, but like everything else
    Dylon wrote, it's an overvalued crock of s**t. I'd wager that in truth
    you get off on the likes of Eminem, 50 Cent, Tupac and Dr. Dre. That's
    where you get your dire attitude problem from, IMO.
    Why wouldn't anyone want to be successful and erudite? Why wouldn't
    anyone want to be able to piss all over jerks like you in debates? Why
    wouldn't anyone want to be able to see through the smoke and cut to
    the quick?
    My youngest (like his siblings) is going to grow up to be just like
    his dear old dad - a chip off the old block - whether he likes it or
    not. It's for the best. The alternative is too horrific to
    contemplate. It's just a tragedy that I can't save him from exposure
    to the poisonous, soul-destroying influences of the rap music culture
    that you so clearly embrase and embody.
    I'm not familiar with that term and I shudder to think what it might
    mean, coming from a foul-mouthed young hudlum like you. Kindly
    preserve my igorance!

    No, I'm simply maintaining my place on the moral high ground.
    We don't all live in a free country, Junior. My right to say what I
    believe has been proscribed by the stinking British government. Just
    think yourself lucky that you're alive and well in a country that's
    only too happy for you to sit in front of your dumb TV shows, jerking
    off at all those topless models.

    There's nothing false about me, Junior.
    Does your mommy know you have access to a computer??
  13. Miles Harris

    Miles Harris Guest

    Come on, you gutless bonehead! Respond and defend your position!
  14. Bob Myers

    Bob Myers Guest

    May I ask - are you under the impression that this is some
    sort of competition, and that you will be awarded some sort
    of prize if you "win"?

    If not, then what is the motivation for the above?

    Bob M.
  15. John Fields

    John Fields Guest

    If you weren't so insistent on fooling yourself into believing that
    you're Mister Oh-So-Wonderful it might be easier for you to see that I
    was alluding to your fear of being exposed for the phony that you are
    by using Dylan's "hiding what you don't know to begin with" line to
    point it out to you.
    Boner??? Is that supposed to be some kind of insult where you come
    from? It doesn't make any sense as an insult here, and I'm pretty
    sure it's not supposed to be a compliment, so unless you care to
    explain it, it'll fall on deaf ears. Even if you do explain what you
    mean though, it probably won't make much difference since most of what
    you say is bullshit, anyway. Case in point, that 9V claim of yours.

    With a terminal voltage of about 2.041V,

    There's no way you can get 9V out of any number of lead-acid cells no
    matter how you choose to arrange them or what kind of a box you put
    them in, LOL! Now, you can't get much more basic than batteries, and
    you obviously don't know what you're talking about even there, so
    you're running at about what so far? Zero for two?
    Rather than just handing you the information, I think it would be a
    good thing if you got off of your fat, lazy, ass and performed that
    little experiment I suggested and then post what you find. I mean,
    after that battery fiasco aren't you even interested in finding out
    whether what you think you know about diodes is true?

    Or, obviously, his acumen.

    If you did you would have noticed that if my persistence is >0, then
    at the lower limit of persistence (which I've been exercising so far)
    my ignorance would be zero.
    Commit them to memory, then. I'm getting kind of bored with it as
    As usual, you're wrong on all counts and the attitude only _seems_
    dire to pukes like you because you're used to people falling for your
    crap and not contesting it.
    If the price of achieving those goals is winding up with a personality
    like yours, I can see why a lot of folks would rather be failures.
    They can try if they want to, but I'll just piss back harder.
    LOL! Because when you finally get the chutzpah to look through the
    smoke what you see will scare you to death?
    You're an idiot. You have no idea who I am or what I believe in, and
    yet you consider yourself fit to make pronouncements based upon your
    opinions, pretty much the same way you've fallen on your face
    pretending you have technical skills.
    And you've been around here for thirteen years without running into
    it? Yeah, right! Go see a Pee-Wee Herman movie.
    No need for me to do that, you're doing an admirable job of it
    Crappola. All you're doing is posturing, pretending that you're
    "above it all".
    Yeah, ours was too until we kicked the British government out of here.
    There's a lot better porn on the net than there is on TV, I'm sure you
    know, and it's not luck that we are where we are. First we had to
    kick out the Brits and lose a lot of lives doing that, then we had to
    jump into WW1 to _save_ the Brits and then, a few years later jump
    into WW2 to save the Brits again. We _all_ lost a lot of lives to
    "save the world", and a little luck here and there helped, but it
    wasn't _all_ serendipetous.
  16. John Fields

    John Fields Guest

    Down, boy!
    You don't get to go out and play much, do you?

    You're used to a leash, so you ought to know it'll be _If_ I choose,
    and _when_ I choose.
  17. Miles Harris

    Miles Harris Guest

    So you're saying I can't get 9V from a lead-acid battery?? And I'm not
    talking about relying on any type of rheostat or voltage-dropper here.
    You're saying it's impossible for me to get 9V out of a lead-acid
    battery by itself alone? Are you serious?
    IOW: "Holy crap! Miles has boxed me into a corner here so rather than
    admit to the fact that I was wrong all along I'll try another
    diversionary tactic."
    Look, Junior, your 'experiment' simply demonstrates that the barrier
    height potential of the Schottky is around half the level of a regular
    silicon diode. You OTOH seem to think they're the same thing and
    therefore interchangeable, presumably. I wonder why they bother to
    I'm certainly not used to having my opinions questioned by a
    snotty-faced school kid, that's for sure. You gotta lot of nerve,
    Junior. Most good folks simply accept what I tell them and go away
    wiser for it. Not so in your case, however. :-(
    You don't like my personality? Sounds like sour grapes on your part,
    I haven't seen any evidence of that yet...
    I've made a good living from my technical skills over the years,
    Junior. People don't pay you good money for being a bonehead. Now,
    isn't it about time you stopped jerking off in front of that computer
    and went back to high school?
    Certainly not. it's beneath my dignity.
    Shame you can't kick them out of *here* as well!
    Britain wasn't occupied in either WW so I don't know where you got
    that lofty idea from. And 'you' were quite happy to sit on the
    sidelines and twiddle your thumbs until the Nips blew Pearl Harbor all
    to hell. If that incident hadn't forced your hand after more than 2
    years of inaction, you'd probably have stayed out of WW2 altogether
    and left us to get on with it alone.

    Correct. To my very great intellectual cost!
    I wonder if entering into discourse with the ignorami can eventually
    result in organic brain damage? :-/
    Time will tell.
  18. John Fields

    John Fields Guest

    Yeah, but I'm not talking about cheating and loading the battery down
    so hard that its internal resistance drops 3V (if it's a 12V battery).

    But, I could be wrong, so what did you have in mind?
    The purpose of the experiment is to prove that your statement that the
    Vf of a silicon junction ("regular")diode is a little over 0.5V is
    wrong. The reason for performing the experiment on a Schottky diode
    as well is to show that the Vf of a Schottky is lower than that of a
    silicon junction diode. So do the experiment and prove that I'm wrong
    and that the Vf of a silicon junction diode _is_ close to 0.5V, or
    shut up.
    Well, yes. I tend to be critical of blowhard self-proclaimed
    purveyors of "Trooth", who do little more than proselytize.
    It's not that _I_ like it or dislike it, I do neither. I look on it
    as just another manifestation of an ego trying desperately to seem
    Selective vision at work...
    Well, you may have made a good living, but if you have to ask for help
    with writing a verbal description of the internal resistance of a
    battery, then I suggest that the quality of your "technical skills"
    is suspect.
    If they're bigger boneheads than you are and you can talk them into it
    they will.
    Actually, you're right. This exchange seems to be little more than
    mental masturbation, and I _do_ need to get some development work
    done, so I think after this post I'll just cut you loose and leave
    you to your own devices.
    OK, then, one more thing you _can't_ do.
    Count me out of that one. We've got enough problems over here without
    taking on yours as well. You fix it.
    Had we not jumped in the first time you would have been, and there
    probably would not have been a Britain to defend the second time.
    Well, we preferred to _try_ to remain neutral, but no... somebody
    always has to start shit and then we get involved in it because we get
    asked to or because we get war declared on us and then everything just
    spirals out of control and it turns into a big ol' war.

    As far as the Japs are concerned, they attacked us on December 7th of
    1941, and we probably would have gone off and just taken care of that
    if it hadn't been for Germany declaring war on us a few days later, so
    maybe it's lucky for you all that in addition to being attacked by the
    Japs, the Germans also declared war on us. We eventually would have
    jumped in to help you guys, we always do, but the German action left
    us little choice about the timeline. Anyway, that's all water under
    the bridge, and what we're _really_ talking about is your technical
  19. Miles Harris

    Miles Harris Guest

    5 cells in series, partially-discharged, powering a small transistor
    I've heard of splitting hairs but this is ridiculous, you insolent
    young pup. You are saying both diodes are essentially the same and
    therefore interchangeable. I'm saying no way; certainly not for all
    applications at the very least.
    You want to be careful with those long words, punk; they'll aggravate
    your acne.
    I don't give a fig for being revered. That's a concern solely for
    lonely, lame-ass losers with a fragile sense of self. Ring any bells?
    You gotta try harder....
    Once again, you misunderstand. That's what comes from listening to too
    much rap music. I can't communicate on the same level as young punks
    like you; that's all there is too it.
    Not at all. They beat a path to my door. I don't even have to
    Translation: "My ass can't take no mo' whuppin' from this Miles guy! I
    need to bail out - and fast!!!"
    BTW, if this "development work" you have in mind is to make your dick
    bigger, you'll find the Swedes make the best devices. ;->
    That'd probably be safer. We're fed up with getting shot-up by your
    gung-ho, narcoleptic troops in these all-too-frequent "friendly-fire"
    incidents. :-(
    Nonsense. We had the largest navy in the world at the outbreak of WW1.
    And the Germans never wanted to wipe us out, anyway. They were our
    biggest admirers! Hitler was a great anglophile; it must have broke
    his heart to bomb us.
    So what's your excuse for invading Vietnam? Or Korea? Or Iraq (to name
    but a few) for that matter? I don't recall any of those countries
    attacking your lame ass.
    I possess none. I must add one point, though: when *your* ass is on
    the line, *we* are just as keen to jump in and help you (for what its
    worth with what's left of our vastly downsized armed forces). We don't
    forget past favors and there's still a lot of affection here for you
    ROTFLOL! I can't help but like you in a strange kind of way. You
    remind me of the son I never had - THANK GOD!!! ;->
    Bwahahahahahaha! Nice one, Junior.
  20. John Fields

    John Fields Guest

    If that's the kind of 'expertise' your clients beat your door down
    for, then they must be beating the door down so they can get you and
    haul your sorry ass into court.
    Not at all. Read it over again.
    Ah! A glimmer of hope! Do the experiment! Learn something!
    You need to be careful with technical words, puke, the way you use
    them they'll aggravate your readers.
    No, and I didn't say "being revered", I said "seem important".
    Sad, isn't it? Instead of you being able to communicate with you, at
    my level, I have to continually stoop to yours.
    "Too" it? Tsk, tsk, tsk...
    Damn! What do you do? Deal crack cocaine?

    It must be _something_ like that, unless you've found a ready market
    for partially depleted batteries...
    Translation: OMIGOD! This Fields guy is going to pull out and leave me
    in the lurch and then I'll have to get back to my tawdry, boring,
    intellectually dead life. "Please, John, Oh Please! I BEG you,
    doooon't leave me like this!
    What, did you manage to get yours hard out to three inches long and
    three-quarters of an inch thick?

    Snipped a bunch of pointless politics...
    Same here. :)
    Same here. :)
    You like the simple stuff, huh?

    Here's one for ya:

    Q: Did you hear about the woman who ate a doorknob?

    A: It turned her stomach! :)
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