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In-circuit Test: how to test Op. Amps

Discussion in 'Embedded' started by zigbee, Apr 8, 2009.

  1. zigbee

    zigbee Guest

    Hi,

    does anybody know how to carry out In-circuit Tests of Operational
    Amplifiers?

    for the sake of knoledge:
    In-circuit tests are carried out by ATE machines with the target
    unpowered (i.e. no power supply)

    I read many Teradyne's articles but couldn't find anything useful.

    thanks for any help,
    Enrico
     
    zigbee, Apr 8, 2009
    #1
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  2. zigbee

    Jim Stewart Guest

    Back when the earth was populated with 709's
    and 741's and I was a bench tech, I'd look to
    see if the two inputs were within a few millivolts
    of each other.
     
    Jim Stewart, Apr 8, 2009
    #2
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  3. zigbee

    zwsdotcom Guest

    In high-volume CE, the _presence_ of _SOMETHING_ on the right circuit
    nodes is used to verify that the chip is present, and a separate,
    powered, functional test is used to check that the circuit is working
    correctly. Or not, as the case may be.

    The question can't be answered without first considering how critical
    the application is. A cheap piece of CE will not be tested
    exhaustively. A life-support system might get somewhat more analysis.
     
    zwsdotcom, Apr 8, 2009
    #3
  4. zigbee

    dkelvey Guest

    Hi
    You can't test an unpowered op-amp. You can
    test the linear devices around it. Testers might
    look for consistant resistance or voltage diode
    drops. This is generally problematic with different
    manufactures.
    As Jim says, when powered up, you should expect
    to see zero volts difference of the + and - inputs. If
    you don't, it may not mean that that amp has gone
    bad but it is usually an indication that something
    related has failed.
    dwight
     
    dkelvey, Apr 10, 2009
    #4
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