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Thread: Op Amp choice

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    Re: Op Amp choice

    Here is the datasheet for the part if you didn't already have a look at it:
    http://ww1.microchip.com/downloads/e...Doc/22041b.pdf.

    There are different surfaces that people are mounting to, so different packages. Pick one that you think you can solder and that will fit your board and its layout.


    Quote Originally Posted by turtle dude  View Original Post
    An ideas why these would be different??? Same part no. different package (by the eye), and why do they make different SM packages? I understand through hole DIP to SM.

    Regards

    Baz.

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    Re: Op Amp choice

    Ok I see, have left data sheet on the printer at work, will have a read through tonight, why the different discription though? Linear/precision/general or should I wait until I've read the data sheet before asking this:sarcy:
    Regard
    Baz

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    Re: Op Amp choice

    Quote Originally Posted by turtle dude  View Original Post
    why the different discription though? Linear/precision/general or should I wait until I've read the data sheet before asking this
    Yes. Only the data sheet matters.

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    Op Amp choice

    Hi Baz,
    You can use any 4 channel low power rail to rail op-amps, no need to go specifically with opa since they are expansive and overkill anyway for this application (5.5mhz). The reason I used them coz I got really good deal on eBay for a lot of 50.. (Plus DIP always will be a little more expansive than SMD).. As for using high resolution ADC without amplifiers, personally I think it won't work as nice as with simple amp circuit.. 12 or 16 bit ADC will only add zeros and if there any noise(and thrust me, there will be a lot of noise..) you will simply read it with higher precision.. Plus precision is not what we after but stable accurate readings. I tried 12 bit ADC without opamp and readings were very unstable.. (Correct me if I'm wrong, Cys also tried using adc without opamp and end up using one in his controller project)
    For the software calibration I will send you a code for reference.
    But, I will be also interested if somebody here can contribute their ideas abut software calibration. Doesn't matter if it's for PIC, AVR or ARM..
    Cheers Nick.


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    Re: Op Amp choice

    I've been using a 24 bit ADC for a couple years now, an LTC 2442. It's way overkill, but I like the part. It works great, and readings are stable to 0.01 mV.







    .
    Last edited by cys; 24th September 2014 at 03:40.

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    Supporting Member nicklinux is an unknown quantity at this point nicklinux's Avatar
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    Op Amp choice

    Quote Originally Posted by cys  View Original Post
    I've been using a 24 bit ADC for a couple years now, an LTC 2442. It's way overkill, but I like the part. It works great, and readings are stable to 0.01 mV.







    .

    That is very interesting chip ! Looks like it comes with integrated amps. "Boosted" signal goes thru adc with 24bit resolution.
    Spi bus also nice ! Did you use existent support library's or wrote your own? Like you said it's a little bit over kill but why not ! $3 extra for the good chip won't kill anybody... Especially when it comes to your own life !



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    Re: Op Amp choice

    I don't boost or amplify the signal at all. The amplifier is used with unity gain (1x) as a buffer. I wrote my own code to run it from scratch using the data sheet as a reference.



    Quote Originally Posted by nicklinux  View Original Post
    That is very interesting chip ! Looks like it comes with integrated amps. "Boosted" signal goes thru adc with 24bit resolution.
    Spi bus also nice ! Did you use existent support library's or wrote your own? Like you said it's a little bit over kill but why not ! $3 extra for the good chip won't kill anybody... Especially when it comes to your own life !



    Sent from my MK15 using electronics pod.

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    Op Amp choice

    Quote Originally Posted by cys  View Original Post
    I don't boost or amplify the signal at all. The amplifier is used with unity gain (1x) as a buffer. I wrote my own code to run it from scratch using the data sheet as a reference.

    Interesting, I've been using arduinos 10 bit adc with terrible results.. Don't know if it's coz layout of the board or long distance between controller board and cell or something else..
    Let me ask you this, do you have a lot of noise during sampling with this chip? I would guess you use delta readings per second for function return to minimize these fluctuations.


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    Re: Op Amp choice

    I don't see any significant noise, and I don't average any values from the part.

    Quote Originally Posted by nicklinux  View Original Post
    Interesting, I've been using arduinos 10 bit adc with terrible results.. Don't know if it's coz layout of the board or long distance between controller board and cell or something else..
    Let me ask you this, do you have a lot of noise during sampling with this chip? I would guess you use delta readings per second for function return to minimize these fluctuations.


    Sent from my MK15 using electronics pod.

  10. #20
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    Re: Op Amp choice

    Quote Originally Posted by cys  View Original Post
    I don't see any significant noise, and I don't average any values from the part.
    Hi cys, if I understand correct you use direct readings from ADC in your project, is this correct?

    Igor P

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