op-amp

Discussion in 'The Projects Forum' started by CircuitSurfer, Sep 30, 2009.

  1. CircuitSurfer

    Thread Starter New Member

    Sep 19, 2009
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    Does anyone know if the pinouts for these two models of op-amps is the same?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    The pin-outs are clearly not the same. The LM741 is a single op amp, the LF358 is a dual.

    Or are you asking something else?
     
  3. CircuitSurfer

    Thread Starter New Member

    Sep 19, 2009
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    0
    I haven't noticed that they are different. Thanks for pointing it out.
    Can you tell me if pins 1,2,3,4 and 8 of LM358 correspond to pins 1,2,3,4 and 8 on LM741.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    The pins do, but the functions differ. One will not substitute for the other.
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    As a general rule of thumb, single op amps follow the same layouts, dual op amps follow the same layouts, and quads follow the same layouts. You can not mix a single with a dual or quad, and so on.

    The LM339, a quad comparitor, has a totally different layout from quad op amps.
     
  6. CircuitSurfer

    Thread Starter New Member

    Sep 19, 2009
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    I realize now that they are different. However my project only calls to use 5 out the 8 pins on the LM358 in effect I think it uses only one of the op-amp circuits. Since LM741 is a single op-amp I want to use that. Having said that what would be the substitute pins 4 and 8 of LM358 on LM741. Or their amplificatoin properties are completely different?
     
  7. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    What five pins do you think the instructor wants you to use?
     
  8. Tahmid

    Active Member

    Jul 2, 2008
    344
    25
    Hi,
    For LM358:
    pin1 = out1
    pin2 = -in1
    pin3 = +in1
    pin4 = gnd
    pin5 = +in2
    pin6 = -in2
    pin7 = out2
    pin8 = vcc

    For 741:
    pin1 = not required
    pin2 = -in
    pin3 = +in
    pin4 = gnd
    pin5 = not required
    pin6 = out
    pin7 = vcc
    pin8 = not required

    Pin4 of 741 and LM358 are the same. Pin8 of LM358 has the same function as pin7 of 741. The rest can be observed from the comparison I have mentioned above.
     
  9. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The opamps are different and might not work if a 741 opamp is used instead of the LM358:
    1) The LM358 works with a supply voltage as low as 3V. The 741 needs 10V or more.
    2) The LM358 works when the input voltages are as low as the negative supply voltage. The 741 does not work unless its input voltages are higher than 3V above the negative supply voltage.
    3) The output of an LM358 can go down as low as the negative supply voltage. The output of a 741 does not go less than about 3V higher than the negative supply voltage.
    4) The LM358 has a low supply current. The 741 has a normal much higher supply current.
     
    Last edited by a moderator: Oct 25, 2009
  10. CircuitSurfer

    Thread Starter New Member

    Sep 19, 2009
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    0
    Thanks for your replies. This is just what I needed to get the confusion out. Will have to replace the 741 since it is so different than the 358. Howver I will still try to make the 741 work. I will post if it will succeed.
     
    Last edited by a moderator: Oct 25, 2009
  11. Audioguru

    New Member

    Dec 20, 2007
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    Instead of the LM358 I use similar but much better MC33171 single opamp, MC33172 dual opamps and MC33174 quad opamps.
    The minimum supply voltage is also 3V and the maximum supply is higher on the new ones.
    The inputs also work at the negative supply voltage.
    The outputs also go to the negative supply voltage.
    They have exactly the same low supply current.

    But the old ones have horrible crossover distortion and the new ones don't.
    The old ones have a poor response above 2kHz and the new ones go up fine to 35kHz.

    I haven't used a 741 or LM358 opamp for about 40 years.
     
    Last edited by a moderator: Oct 25, 2009
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