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CD4050AE vs CD4050BE

Discussion in 'Electronic Design' started by logjam, May 27, 2007.

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  1. logjam

    logjam Guest

    I have a project that requires a 4050. I bought around 50 CD4050BE
    ICs, but none of them work in place of the old (vintage 1975)

    I lifted legs 2 and 3 out of the IC socket, attached my scope to leg 2
    and connected leg 3 to leg 1. This should have caused pin 2 to go
    high according to the data sheet. The input threshold for high is
    supposed to be 3.5v. Pin 8 is a good hard ground. The voltage supply
    is 5.02v. The CD4050BE (new ones) were pulling the inputs down from
    4.5-5v down to 2.5v (there is a 47ohm resistor in front of the
    inputs). With the CD4050AE part the inputs are not pulled down.

    So either I got an entire tube of bad parts, or the AE / BE indicates
    something important? I haven't been able to find a data sheet
    specifically for the CD4050AE.

    I have tested a vintage 1975 MC14050CP is known to work in place of
    the CD4050AE for this application.

    I will continue to try to find the data sheet.

    Right now I am going crazy. I have tried 8 or so parts from the
    tube. I wouldn't imagine the whole tube would be bad. Even in a test
    circuit I can't get anything out of them... : ( Even if the voltage
    was not high enough to be "high", it was sure loading the inputs a

  2. DaveM

    DaveM Guest

    Download the CD4050A datasheet from

    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

    Life is like a roll of toilet paper; the closer to the end, the faster it goes.
  3. logjam

    logjam Guest

    Unicorn Electronics. I have never had a problem with anything from
    there before... I can't help but think that there might be a
    difference between the AE and BE suffix???

    If the device were damaged by static, is it possible that the inputs
    would have more load?

  4. Bob

    Bob Guest

    The 4xxxB family has a has added input diodes for ESD protection. There may
    be more differences, but I'm not sure.

    I never had any trouble with the B family, but the A parts I used to get
    from Radio Shack had a high failure rate. This, however, was a LONG time

  5. Where did you buy these parts?

    Best regards,
    Spehro Pefhany
  6. Al

    Al Guest

    If I remember correctly, the A series had a max. voltage of 10 whereas the
    B series has a max. voltage of 20. The high and low logic levels are 90% or
    18V when supplied by 20V and 10% or 2 volts for the B series. The high and
    low levels for 10 volts series are 9 and 1, respectively. So a logic high
    would have to be 9 volts or above or for a logic low 1 volt or below. The
    higher values provide more noise immunity. At least that was the thought.
    I'm not sure the B series would work well with a supply voltage of 5V. As
    this is all from memory, take it with a bit of salt.

    I think I have some old databooks lying around and will take a look.

  7. There should be virtually no current going into or out of the inputs
    for applied voltages of 0..12V, even with the Vcc open or shorted to
    Vss. Either they are entirely fried, your pin numbers are wrong, or
    they are actually a different kind of part.

    Best regards,
    Spehro Pefhany
  8. My memory is that the 4000 series cmos had a voltage range from 3 to 18 from
    the getgo. If I'm not mistaken, the B suffix were buffered and had a hard
    time being forced into such things as analog amplifiers and oscillators.

    The guaranteed OUTput of the 4000 series is (as a percentage of Vdd) 90%
    high and 10% low, while the INput had guaranteed switching rates of 70% and
    30% respectively. You always had a guaranteed noise margin of 20%, 3.6
    volts at 18 volts Vdd and 1 volt at 5 volts Vdd.


  9. Ross Herbert

    Ross Herbert Guest

    My recollections are similar. I know that there were definite areas
    where buffered CMOS could not be interchanged for unbuffered devices.

    This TI document refers to this fact in the background paragraph.

    While this doc specifies unbuffered devices as being marked UB I think
    this only applied well after the introduction of the buffered series.
    Initially, only the RCA 4000 (unbuffered) series existed and I think
    they may have begun to use the A suffix to differentiate from the B
    series when the latter started to appear more commonly. My old RCA
    literature may have some further info.
  10. There is little difference except that the -B version
    has a higher supply and input voltage range.

    The 4050 does have a weakness on the inputs. It is
    designed to operate with a logic 1 that can exceed
    the Vcc, up to 20V for the 4050B. In order to do
    this there is little or no protection against a
    positive input overvoltage.

    Your apparent high current taken by the inputs does
    suggest damaged parts.
  11. whit3rd

    whit3rd Guest

    My old RCA CMOS databook has both data sheets; the main difference
    is that the 'B' is good for 3-18V power, and the 'A' is good for 3-12V
    power. Input limits are 20V for 'B' and 12V for 'A'. Both are
    to be driven from higher voltage than the power supply.

    (+) power is on pin 1, (-) power is on pin 8.

    Other differences are minor (guaranteed sink current at 5V is 3.2 mA
    for the 'B' and 3 mA for 'A').
  12. Tim Shoppa

    Tim Shoppa Guest

    Are you sure you got real CD4050BE's? Motorola had a part line with
    numbers beginning like 40xx but they were Motorola's own version of
    TTL and had nothing to do with the similar CD-series CMOS parts.

    It's hard to imagine them being counterfeit parts - it'd be like
    counterfeiting pennies! - but on the surplus market large batches of
    mislabeled or just plain defective parts show up quite regularly. The
    older the chips, or the lower in the distribution chain you go, the
    more likely what you got were factory rejects or floor sweepings. Are
    you sure you didn't get these through a time warp from Poly Paks?

  13. Tim Shoppa

    Tim Shoppa Guest

    Ahah! Now I remember, the MC4050 was a decade counter and maybe a
    display decoder used in lots of 70's/80's vintage frequency counters.
    It won't work nothin like a CD4050.

  14. But the OP specifically said "CD4050BE", which is nothin' like
    "MC4050". But maybe the parts are marked differently from what s/he
    thinks they are.

    Best regards,
    Spehro Pefhany
  15. Precisely.

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