Discussion in 'General Electronics Chat' started by *synonymous*, Dec 16, 2013.

  1. *synonymous*

    Thread Starter Member

    Nov 29, 2013
    Hello! and thank you!

    What is a good way to determine a power supply voltage for a given OpAmp?
    If I intend to have a few volt at maximum signal to manage, what real difference does it make to create a power supply with a voltage larger than the OpAmp is designed to work with? If this OpAmp works to within 1 volt of the rail supply, is it really going to make any difference or be better to make a supply of a greater than 1 volt-to-signal? I understand creating a safe cushion, but lets then say, is there a benefit to creating a supply of more than double the signal? What is generally sought after in designing such a circuit?

    Thanks again!
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
    Why bother?

    You want a supply that is twice the input signal? Then just buy op amp that has that feature.
  3. crutschow


    Mar 14, 2008
    Generally you don't need a supply voltage greater than that required to generate the maximum output voltage. This minimizes power dissipation in the op amp. Standard op amps generally require the supply voltage be a couple volts or so greater than the peak output voltage (plus and minus). Rail-rail type amps can typically operate to within a few tens of millivolts of the supply voltages, depending upon the output load. In either case the op amp data sheet will show what is required. Note that you must always have the minimum supply voltage applied, also as stated in the data sheet.
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    just make sure whether you are going to need a double ended supply, such as +12 and -12 or a single ended supply. some of the older ones need a double ended supply to prevent a "lock up" if you get the input voltage wrong.
  5. *synonymous*

    Thread Starter Member

    Nov 29, 2013

    The OpAmp in question is the LME49740 and I plan to power it +- 6V supply for a line level audio signal. The datasheet says it's good for +-2.5V to +-17V, so I assume based on the above comments that what I plan is about ideal. Any higher voltages and it's just added dissipation for the OpAmp

    Thanks again!