741amplifier practical; working circuit

Discussion in 'General Electronics Chat' started by diwa2000@gmail.com, Jun 19, 2008.

  1. diwa2000@gmail.com

    Thread Starter Active Member

    Apr 15, 2008
    40
    0
    guys can any one please help with the proper circuit diagram/ connection diagram of how to set up a LM741 opamp as a amplifier. as I have tried number of times Im not able to receive any amplification. It would be very kind of you if you could please let me know the (+5) and (-5) connections to be done and what to do about the common ground that comes out by making a +5 and -5 connection.any information needed please post back.
    by the way Im using the LM741 amplifier to trigger the timer 555 circuit which requires 1/3Vcc. My case Vcc is +5V.
    Please help.
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    Here are schematics with formulas to calculate the opamp amplifier.

    Greetings,
    Bertus
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Since your lousy old 741 opamp has a positive 5V and a negative 5V supply, its output will go to -3.8V which might blow up the input of the 555 that should never go below 0V.

    An old LM358 dual opamp and an MC33171 and an MC34071 operate from a single positive 5V supply (minimum 3.0V). Their outputs go very close to 0V and up to about +3.8V when they have a positive 5V supply.
     
  4. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,438
    368
    Yes, dump the 741. I can think of no use for it in 2008.
     
  5. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,438
    368
    "Hello Blocco
    thanks for a wonderful answer ....I was just expecting that....If you could possibly not help in a situation like this at least dont comment like this. I have the use of LM741 in my project...thats why Im making use of it. Please dont do like this to others.
    Take care
    Regards"

    You don't need to PM, the advice is good. There are much better op-amps available that run at single supply and drive rail to rail. Just because you have a 741 does not mean you have to use it.

    If you want to make life more difficult for yourself by using an archaic device then please do so.
     
  6. acebodge1

    Member

    Jun 18, 2008
    13
    0
    hiya folks,a handy book i`ve used is forrest mimms circuit scrapbook,loads of usefull stuff for the begginer,doesn`t cover everythin`tho`,some handy stuff about using op amps in it.
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    For most low freq aplications the 741 is a good part, I tend to use its cousin, the 1458, because you have 2 op amps in one 8 pin package, but for your application it should definately be good enough. What is your current schematic?

    A good section to review on op amps is the AAC eBook Vol III Chapter 8.

    Dual supplies aren't absolutely necessary, but I suspect this part will have some problem using 5 Volt, it needs more. LM741 Datasheet

    Even +/- 5V might not be enough, for this reason you might need to use something else. An LM339 would do nicely, but a pull up resistor is required on the output. LM339 Datasheet

    Here is how I would do it...

    [​IMG]

    Note: This is a quad part, 4 for the price of 1. The other parts need connected as shown to eliminate undesirable side effects.
     
    Last edited: Jun 19, 2008
  8. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Hi Bill,
    An LM339 quad comparator does not have the frequency compensation capacitors of an opamp so it cannot be used with negative feedback like an opamp.
    An LM324 quad opamp has the same front end as an LM339 but it has frequency compensation capacitors.
     
  9. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    The LM339 will go down to 2V on the power supply, which is why I grabbed it. For OP reference, here is the LM324 Datasheet. It can use as little as 3V for power. Thanks AG.

    It's also a quad, so same rules for extra op amps apply. Pretty close to a 741 overall.
     
Loading...