Ca3140

Discussion in 'The Projects Forum' started by Msinks, Mar 5, 2012.

  1. Msinks

    Thread Starter New Member

    Mar 3, 2012
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    I need a replacement for CA3140. I came across TL082CP. Can it work as a sub?
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,649
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    Hello,

    It depends on the needs.
    The CA3140 has offset inputs and a strobe pin.

    [​IMG]

    The TL082 is a dual opamp with none of those pins.

    [​IMG]

    The TL081 does have offset inputs, but no strobe input.

    I have attached the datasheets for both.

    Bertus
     
  3. Msinks

    Thread Starter New Member

    Mar 3, 2012
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    My circuit shows me that i only need pins 2,3,4,6 and 7 from the CA3140. from the info u gave me, am worried pin 6 does not macth with that on the TL082.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,649
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    Hello,

    The TL081 ia almost pin compatable.
    That way the PCB (if used) does not need any changes.

    Bertus
     
  5. Msinks

    Thread Starter New Member

    Mar 3, 2012
    22
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    thanks bertus, u rock
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    You need to post the schematic of the circuit you want to substitute the opamp in.

    The TL08x series has a common mode input that ranges from -V +3v to +V -1.5v; in other words, it won't "see" input that is within 3v of the negative supply, or within 1.5v of the positive supply. The CA3140 has a much wider common mode input range.

    Many of the newer opamps are not available in DIP packages; they are SMT/SMD only. You need to say whether you are building a new circuit based on an old design, or repairing an existing circuit.

    Intersil still makes the CA3140; and it is available from AvnetExpress.com, Digikey.com, Newark.com, Element14.com, and some other authorized vendors.
    Example:
    http://avnetexpress.avnet.com/store...201&action=products&N=0&mfr=ITS&term=CA3140EZ

    Since it's still available, it would be a good idea to use the specified part.
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    896
    The input voltage range of the CA3140 is completely different to the TL081:
    1) The input of the CA3140 can go a little below its negative supply voltage.
    2) The input of a TL081 has the "Opamp Phase Inversion Problem" so if its input gets within 3V from the negative supply then the output suddenly goes positive.

    The minimum supply for a CA3140 is 4V. The minimum supply for a TL081 is 7V.
     
  8. Msinks

    Thread Starter New Member

    Mar 3, 2012
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  9. SgtWookie

    Expert

    Jul 17, 2007
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    If you had tried to use a TL081 with that circuit, the output LEDs would never have turned off, as the output would not fall below 3v.

    I don't know what was specified for LED0. If it's a typical IR LED, then the Vf would be ~1.2V, and so (12v-1.2v)/27 Ohms works out to be around 400mA. That will fry most IR LEDs.
     
  10. Msinks

    Thread Starter New Member

    Mar 3, 2012
    22
    0
    thanks for help guys
     
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