LM358 single version

Discussion in 'General Electronics Chat' started by Zeebit, Nov 20, 2013.

  1. Zeebit

    Thread Starter Member

    Nov 8, 2013
    72
    0
    Is there a single op amp version of the LM358?
    Is there any other single opamp that has the same or almost the same specs as the LM358?

    I've tried googling but it is not very helpful.
     
  2. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    1,190
    156
    Most times I just write down the spec and go on mouser and search the specs and go from there....
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,033
    Most folks just use one of the two in the package. Voila, a single op-amp.
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,421
    3,357
  5. Zeebit

    Thread Starter Member

    Nov 8, 2013
    72
    0
    I am trying to make the pcb as small as possible so I would like to avoid tying the unused op amp to save space.

    Circuit:
    http://dl.dropboxusercontent.com/u/1181169/easylpm.PNG

    This circuit is to be used in a laser power meter. The sensor is a TEC module and the output is hooked to a voltmeter.
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,033
    Fair enough. What package are you looking at? (thru-hole, surface mount?)
     
  7. Meixner

    Member

    Sep 26, 2011
    116
    21
    I have done that before,the connections to the unused op amp can be made under the IC package. That way it does not use additional space on the PCB.
     
  8. Zeebit

    Thread Starter Member

    Nov 8, 2013
    72
    0
    Never mind. What resistor values are ideal for terminating unused op amps? will two 500K ohms suffice?
     
    Last edited: Nov 20, 2013
  9. Meixner

    Member

    Sep 26, 2011
    116
    21
    I don't use resistors, I tie the output to the - input and ground the + input.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Before wiring an unused channel as a unity-gain voltage follower, make certain that the opamp is unity-gain stable; as quite a few are not.
     
  11. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    The LM358 is absolutely unity gain stable and also allows inputs to be tied to the negative rail so you can ground them even if it is single supply application.
     
  12. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    Is the - output the return? If so, you could wire the unused op amp as a follower and use it's output as the return node. That would give a lower impedance for the return and the resistor divider on the input of that op amp could be higher Ohmic value which would save wasted current burned off the battery.

    There are also some micropower op amps around that will significantly reduce quiescent current drawn off the 9V rail.
     
Loading...