inverting circuit diagram using uA 741

Discussion in 'General Electronics Chat' started by Adnan Samra, Feb 10, 2008.

  1. Adnan Samra

    Thread Starter New Member

    Feb 10, 2008
    7
    0
    hi guys,
    I was wondering if any one could send me an inverting circuit diagram using uA 741 op I need it to trigger a triac for a ups design so that when the pulse is applied to inverting input the out put would be zero and triac will not work and visa versa could any one help me?
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    An inverting OpAmp will output a negative level with a positive input, and a positive level with a negative input.

    http://www.allaboutcircuits.com/vol_3/chpt_8/3.html

    If you must, for some reason, limit yourself to the UA741, you could use a diode to clamp the negative signal to no more than -0.7V. But it would be better to use a comparator, such as the LM311, LM393, or LM339. You might need a transistor of some kind to "beef up" the output of the comparator.

    For that matter, you might be able to use a simple transistor inverting amplifier (Common emitter or common source) and dispense with a chip altogether.
     
  3. Adnan Samra

    Thread Starter New Member

    Feb 10, 2008
    7
    0
    well the triac wont work all the same because it locks on on state once initialized I really need to trigger a darlington transistor that can tolerate 3A load with a 741 op any diagram that can help me or even using a comparator please?
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Do we understand that you are trying to control DC and not AC current?
     
  5. Adnan Samra

    Thread Starter New Member

    Feb 10, 2008
    7
    0
    Yes I am,
    let us forget about the triac Hi, everyone
    can any one help me with this task?
    I need to do the following :
    1- use an inverting op to switch on a darlington transistor to feed 1.3 A of 12V
    I need to do this because I need to make a dc usp , the concept I am thinking of is the following :
    when Main electricity is on using 220AC/12VDC adaptor a signal taken from that dc is to be fed to an inverting OP so that the out put of the op is null and once main electricity is off then the op inverter cercuit should give a signal to the darlington transistor to switch onthe (+) polar of the backup battery to the load , this whole circuit will be fed from back up battery so that it will always stay on whether the main is on or not , so once main power is on again the out put of op will be off again and so the darlington circuit will switch off power from Back up battery, what do you think ?
    is this good enough ? any ideas or diagrams to do this?
     
  6. Adnan Samra

    Thread Starter New Member

    Feb 10, 2008
    7
    0
    my problem was solved when I used 741 in shmitt trigger configuration followed by a TIP 102 Darlington transistor with the right base resistor I can handle big loads in several amperes, thank you
     
Loading...