Can I swap these parts?

Discussion in 'General Electronics Chat' started by Jacob J, Apr 29, 2011.

  1. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
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    Hey all

    I have two swap questions:

    1. can I swap a PN200 with a BC640 PNP transistor? Is it possible to swap these two or any other suggestions to an alternative swap?

    2. Can I swap a LM741 with a TL071CP? Any other suggestions to an alternative swap?

    Thanks in advance!

    /Jacob
     
  2. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
    159
    0
    Hmm could I use a LM393N comparator instead of the LM741 or the other way around maybe, so I dont need to have both a LM393N and a LM741 (or TL071CP).
     
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
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    The BC640 datasheet shows lower minimum current gains than for the PN200, so it may not be a good replacement.
    http://www12.fairchildsemi.com/ds/BC/BC640.pdf
    http://www.fairchildsemi.com/ds/PN/PN200A.pdf

    The TL071 is probably better than the 741 in most respects. Check the details for yourself:
    http://www.national.com/ds/LM/LM741.pdf
    http://focus.ti.com/lit/ds/symlink/tl071.pdf

    You may be able to use an op-amp as a comparator in some situations, but note that op-amps do not usually have open-collector outputs.

    Comparators can't normally be used to replace op-amps - apart from the open-collector output they are not designed for use as stable negative feedback amplifiers.
     
  4. Jacob J

    Thread Starter Active Member

    Jun 18, 2009
    159
    0
  5. Adjuster

    Well-Known Member

    Dec 26, 2010
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    The BC557 seems to have a significantly lower ft, 100MHz compared to 250MHz for the PN200, which might or might not be a problem depending what you want the transistor for. There may of course be other differences - look at the datasheets for yourself.

    I don't know what your application requires, so it's not clear what would be critical. Finding completely equivalent devices can be difficult, so it may help to know what parameters may be most important for a given circuit.
     
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