1. rohitprakash

    Thread Starter New Member

    Mar 13, 2013
    5
    0
    what is the role of negative supply in opamp. we can make circuit also with single supply. please help...
     
  2. Pramod101092

    New Member

    Mar 12, 2013
    1
    0
    Hmm i also hav d same prblm
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,033
    3,241
    Here are some reasons you would want a negative supply:

    If the op amp is not a rail-rail type you will need a negative supply for the input and/or output to go to zero volts.

    If the op amp is a rail-rail type then you will need negative supply if the signal goes below zero volts (such as an AC signal with average value of 0V) and you want the DC value of the signal to be preserved.
     
    rohitprakash likes this.
  4. rohitprakash

    Thread Starter New Member

    Mar 13, 2013
    5
    0
    please. elaborate it....
     
  5. #12

    Expert

    Nov 30, 2010
    16,330
    6,818
    If the amplifier does not have a negative supply voltage, it can not output a negative voltage. Many amplifiers can not input a negative voltage if they do not have a negative power supply voltage. Therefore, the role of a negative supply voltage is to enable the amplifier to take in and put out negative voltages. The amplifier chip can not make negative power supply voltages for itself.
     
    rohitprakash likes this.
  6. rohitprakash

    Thread Starter New Member

    Mar 13, 2013
    5
    0
    but if we will use a coupling capacitor in the output we can get the negative voltage for ac input..
     
  7. #12

    Expert

    Nov 30, 2010
    16,330
    6,818
    Now you are talking about a specific circuit which we do not know about. Please post a drawing of the circuit.
     
  8. rohitprakash

    Thread Starter New Member

    Mar 13, 2013
    5
    0
  9. #12

    Expert

    Nov 30, 2010
    16,330
    6,818
    I see that you posted but the picture didn't come through. Probably stuck in the self protecting features of the site. It denies some content by people with very little history here until a moderator approves it.
     
  10. rohitprakash

    Thread Starter New Member

    Mar 13, 2013
    5
    0
    i was saying that single supply opamp circuit can be used but why we use negative supply.....
     
  11. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,394
    1,606
    Because a coupling capacitor will *always* introduce frequency response artifacts.

    A dual supply (both positive and negative) has a nice zero volt reference point available to amplify signals against. "Zero" can be used as both an input an output reference/return point.

    A typical dual supply op amp has no idea the supply is a dual supply. It will work to full specification with a single supply if signals are referenced to a suitable point.
     
  12. ramancini8

    Member

    Jul 18, 2012
    442
    118
    If you don't like dual supply op amps don't use them. There is a lot of literature that covers single supply circuit design using op amps.
     
Loading...