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LOG101: Is good idea replace LOG101 to LOG114

SeongJae Park
Prodigy 20 points

Part Number: LOG101
Other Parts Discussed in Thread: LOG114, LOG200

Tool/software:

As I said at title, I consider replace LOG101. It's such an old IC that I think it might be discontinued in the future.

So I consider LOG114.

This idea worth it? Please Give to me answer before follow condition.

1. The temperature range of new logamp must equal or greater then LOG101.(I confuse temperature range of LOG114 is 0 ~ 70 or -40 ~ 85. What I follow temperature factor?)

2. The price of a new log amp similar to the LOG101 should be as similar as possible.

3. What are some of the same behaviors as the existing LOG101?

thank you!

  • 0
    TI__Guru 55466 points

    HI Seong Jae,

    The upcoming LOG200 (on preview) and LOG114 (released) are newer logarithmic amplifiers that may be of interest, although these devices are not an exact pin-to-pin replacement to the LOG101 but offer similar functionality. The LOG114 is in production, while the LOG200 is on preview status, expected to release to production later this last quarter of 2024.

    The LOG200 is a high speed precision logarithmic amplifier with integrated photodiode adaptive biasing, two voltage references, and auxiliary op-amp (currently on preview status). The LOG114 is a precision high-speed logarithmic amplifier with a 2.5V Reference and auxiliary Op Amp.  See links below:

    www.ti.com/.../LOG200

    https://www.ti.com/product/LOG114

    Here is a link for a comparison table between the LOG200, LOG114, and LOG101:

    There are differences in the transfer functions, scale factor, and specifications for these devices as shown on the table above.  The LOG200 offers specifications from 0 to +85C temperature, as well as over the extended temperature range, -40C to +125C.

    If you would like us to review your LOG101 schematic, please post the schematic, and provide information on the current ranges on this application that need to be measured, as well as critical performance specifications on the system.  Let us know and we will happy to review/provide suggestions,

    Thank you and Best Regards,

    Luis

  • 0 in reply to Luis Chioye
    Prodigy 20 points

    Thank you for your answer.

    1. So temperature range of LOG114 is 0 ~ 70? According datasheet, its -40 ~ 85 maybe datasheet wrote wrong right?

    2. And what  that mean of extended temperature and specification temperature? Is specification temperature means tested?

    The LOG101 using for logarithm amplification of photodiode current signal and it work on 0 ~ 70 of temperature range. As a result, LOG114 didn't satisfying condition what I want. Maybe LOG200 is best choice I think.

    I want show some schematic for you but I don't want open other people...

  • 0 in reply to SeongJae Park
    TI__Guru 55466 points

    Hi Seong,

    Although the LOG114  (released on 2007) operates/functions over the  -40C to +85C, the LOG114 accuracy min/max specifications are only specified for the ambient temperature range of -5C to +75C as shown on the Electrical characteristics Table on pages 3 to page 6. Hence, for practical purposes, the LOG114 data sheet only provides  performance assurances within the -5C to +75C range.

    The LOG200 is a newer device, and the data sheet offers min/max performance specifications over the 0C to 85C temp range, as well as min/max performance spec for the extended temperature range (-40C to +125C). 

    One comment, the leakage current on photosensors often becomes a dominant source of error and limiting factor at ambient high temperatures above +85C; limiting the ability to measure low level photodiode currents.  On many photodiode data sheets, the photosensor diode performance is only specified over a limited temperature range from -40C to +85C for this reason. 

    As you can see, both the LOG114 and LOG200 cover well the complete 0C to 70C without performance issues.

     I will contact you via E2E private message shortly, so you can share your schematic and application details via private conversation. 

    Thank you and Best Regards,

    Luis