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Hot![Solved] : Alternative Part Number of Operational Amplifier OP07

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karan123
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2020/09/14 11:33:32 (permalink)
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[Solved] : Alternative Part Number of Operational Amplifier OP07

Hi,

Is there any alternative Part Number of OP07 from microchip or any other company?

--
Thanks
post edited by karan123 - 2020/09/18 21:22:21
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    Antipodean
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    Re: Alternative Part Number of Operational Amplifier OP07 2020/09/14 12:02:10 (permalink)
    +1 (1)
    karan123
    Hi,
    Is there any alternative Part Number of OP07 from microchip or any other company?
    --
    Thanks



    Do Microchip make an OP07? I didn't think they did. It is a very old part originally made by Burr-Brown which has been absorbed by TI. various other companies second sourced it.
     

    Do not use my alias in your message body when replying, your message will disappear ...

    Alan
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    PStechPaul
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    Re: Alternative Part Number of Operational Amplifier OP07 2020/09/14 18:40:53 (permalink)
    +1 (1)
    The OP07 is still available from Digikey for as little as 50 cents in single quantities. There is also an OP77 which has improved specs, but costs $10 or more. They are made by Analog Devices and Texas Instruments.

     
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    karan123
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    Re: Alternative Part Number of Operational Amplifier OP07 2020/09/14 19:22:26 (permalink)
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    PStechPaul
    The OP07 is still available from Digikey for as little as 50 cents in single quantities. There is also an OP77 which has improved specs, but costs $10 or more. They are made by Analog Devices and Texas Instruments.


    Thanks both of you...

    Is there any part number that has matched specs with OP07 plus auto nulling in which TRIMing (as on Pin 1 and 8) will not needed.


    --
    Karan
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    PStechPaul
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    Re: Alternative Part Number of Operational Amplifier OP07 2020/09/14 19:56:38 (permalink)
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    The OP77E has typical 10 uV offset and maximum 20 uV, so nulling may not be necessary. The OP-07A has similar specs. Chopper stabilized op-amps can get down to around 5 uV, but there are limitations. What are your actual needs? There may be better options, such as instrumentation amplifiers.

     
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    karan123
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    Re: Alternative Part Number of Operational Amplifier OP07 2020/09/14 22:02:03 (permalink)
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    PStechPaul
    The OP77E has typical 10 uV offset and maximum 20 uV, so nulling may not be necessary. The OP-07A has similar specs. Chopper stabilized op-amps can get down to around 5 uV, but there are limitations. What are your actual needs? There may be better options, such as instrumentation amplifiers.

    Application is used as Integrator for Rogowski Coil.
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    PStechPaul
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    Re: Alternative Part Number of Operational Amplifier OP07 2020/09/15 22:01:11 (permalink)
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    I use an AD620 or INA118 with two 200k resistors and a 220 nF Polypropylene capacitor for that. The ens of the Rogowski coil connect to 1k resistors tied to GND. Works fine for an instrument which can measure currents from about 20 amps to as high as 100,000 amps to better than 1% accuracy.

     
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    karan123
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    Re: Alternative Part Number of Operational Amplifier OP07 2020/09/16 20:18:22 (permalink)
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    Hi

    Thanks..

    1) AD620 and 1NA118 are instrumentation amplifier. How they are better for intergrator then general OpAmp like (OP07) ?

    2) Do you any idea of waveform for Rogowski coil before or after (Internal)Differentiator
    and
    Before or After (External) Integrator. ?

    --
    Karan
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    PStechPaul
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    Re: Alternative Part Number of Operational Amplifier OP07 2020/09/17 02:20:55 (permalink)
    +2 (2)
    The Rogowski coil measures magnetic field, which is the derivative (or differential) of the current through the conductor it's wrapped around. Thus, for a steady pure sine wave of fixed frequency, it will be a sine wave (or perhaps more accurately a cosine wave). But as it produces a voltage proportional to rate of change of current, it will have very high voltage spikes if the current suddenly changes, or otherwise has high frequency components. A practical R-C integrator will reconstruct the original current waveform, within certain limits, determined by the values of resistance and capacitance. If the integrator is comprised of two high value resistors and a capacitor, the voltage on the capacitor will be well within the normal mode range of the inputs of a instrumentation (differential) amplifier, so the high voltages that can be produced by the Rogowski coil will be limited, and the resistors (along with zeners or other protection devices) can protect the amplifier.
     
    An "ideal" op-amp integrator will use a series resistor and a capacitor as feedback from output to input, but because an op-amp does not have infinite gain nor zero offset voltage and current, the output will drift when the input voltage does not change. So you must either preset the circuit to initial conditions before applying the signal to be integrated, or you can add resistance across the capacitor which will eventually discharge it and stabilize the output to a known condition. But the output will only have the correct value for a period of time determined by the RC time constant.
     
    I have found that using an instrumentation amplifier with two resistors and one capacitor provides a good integration of signals in the power line range, including reasonable representation of the actual current waveform. I also use two 1k resistors from each end of the Rogowski coil to provide a ground reference, and a shielded pair cable from the coil to the integrator presents a balanced signal which is relatively immune to induced noise, especially when the conductor pairs are twisted inside the grounded shield. I could not find specific examples of this configuration, but it has proven to be reliable and accurate in instrumentation similar to your welding current application.
     
    https://en.wikipedia.org/wiki/Op_amp_integrator
     
    https://www.electronicshub.org/operational-amplifier-as-integrator/
     
    https://www.analog.com/media/en/training-seminars/design-handbooks/designers-guide-instrument-amps-complete.pdf
     
     

     
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