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    CA3130 Equivalent with lower supply voltage

    Hi!

    I am using 2 CA3130 on my PCB. The problem is it requires 5V supply voltage. It is not convenient for my circuit where everything else needs <= 3.3V

    Do you know of any other op-amp that could replace this CA3130?

    The characteristics of the circuit: It is for EEG amplification
    - Low input curent (<mA)
    - Low input voltage (uV)
    - Low frequencies (< 60 Hz)

    I want to use that op-amp as an amplifier + filter.

    Thank you!

    Kali

    •   Alt21st June 2016, 13:43

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    Re: CA3130 Equivalent with lower supply voltage

    Hi,

    you should mention whether SO-8 or DIP.

    ****
    If I need to select one I´d go to a distributor and use the interactive selection tool.

    Farnell and many other have those internet sites.

    Klaus



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    Re: CA3130 Equivalent with lower supply voltage

    If your board is really old, it may even be an older package, a round metal can similar to the TO39.

    The CA3130 was externally compensated, because at the time it was designed, the typical slew rate for internally compensated opamps was very slow. Only between 0.5 to 2.0 V/us.
    Newer opamps have far larger bandwidths, so you can safely clip out that capacitor.

    The real question is: do you require the strobe function?
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    Re: CA3130 Equivalent with lower supply voltage

    I'm very sorry for the delay, I completely forgot to come back here and had other projects on my mind.

    To answer your questions, the package I use is a SOIC. Here is the exact model: http://uk.farnell.com/1018162. Also I don't need a specific package as I can just redo the PCB if needed.
    It is actually a new PCB: I am designing it right now. I would like to use a battery as a power supply and it would be more convenient to have <5V as an input.

    Concerning the strobe function, the only thing I do is to link the pin 8 (strobe) to the 1 (offset) with a 1nF capacitor because I read that it's better for the stability of the op-amp. (I think it's the external compensation you refer to)

    Edit: Here is what I found on Farnell, what do you think?
    http://fr.farnell.com/analog-devices...-vf/dp/9425713
    http://fr.farnell.com/linear-technol...ise/dp/1330753
    Last edited by kalifed; 10th July 2016 at 10:51.



    •   Alt10th July 2016, 10:25

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    FvM
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    Re: CA3130 Equivalent with lower supply voltage

    Very unlikely that you want to use a multi 100 MHz bandwidth OP as CA3130 replacement.



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    Re: CA3130 Equivalent with lower supply voltage

    Quote Originally Posted by FvM View Post
    Very unlikely that you want to use a multi 100 MHz bandwidth OP as CA3130 replacement.
    Thank you for your answer. Could you elaborate a bit? If the bandwidth is higher than for the CA3130 it doesn't matter, right?

    I mean: the CA3130 has a 15MHz bandwidth, which is already way above what I need (60Hz)

    Unless I am making a mistake somewhere?



    •   Alt11th July 2016, 03:22

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    Re: CA3130 Equivalent with lower supply voltage

    A high-bandwidth OP is difficult to handle. It's likely to fall into parasitic oscillations if not properly bypassed. It probably never works stable on a breadboard. It has higher quiescent current than necessary.

    There are so many low voltage general purpose OPs with 1 - 10 MHz bandwidth.


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    Re: CA3130 Equivalent with lower supply voltage

    Quote Originally Posted by FvM View Post
    A high-bandwidth OP is difficult to handle. It's likely to fall into parasitic oscillations if not properly bypassed. It probably never works stable on a breadboard. It has higher quiescent current than necessary.

    There are so many low voltage general purpose OPs with 1 - 10 MHz bandwidth.

    Following your advices I found that one:
    http://fr.farnell.com/2376717

    To me more precise, I have an input signal of 2mV amplitude and up to 60Hz. Does it mean that I need at least 2mV * 60Hz = 0.12V/us for the slew rate?



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    Re: CA3130 Equivalent with lower supply voltage

    My math tells that the maximum slew rate of a 2 mV 60 Hz sine is about 0.75 V/s. But slew rate is measured for the OP output, so required slew rate depends on which output is generated by the 2 mV signal.



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    Re: CA3130 Equivalent with lower supply voltage

    Quote Originally Posted by FvM View Post
    My math tells that the maximum slew rate of a 2 mV 60 Hz sine is about 0.75 V/s. But slew rate is measured for the OP output, so required slew rate depends on which output is generated by the 2 mV signal.
    Yes, you are right. I forgot the 2pi factor...

    So after some research, I think I found the ideal replacement for my CA3130 : http://uk.farnell.com/1651305

    I made a table to compare what I believe to be the most important characteristics.
    2016-07-16-08-55-04.png

    What do you think? (It is a Dual but I actually need 2 op-amps so it's not a problem)



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