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LM319 - Input voltage range

Hirotaka Matsumoto
Guru 27565 points
Other Parts Discussed in Thread: TLV3201, TLV3502, LMV7235, TLV3202, LM119

Hello all,

Would you mind if we ask LM319?

<Question1>
In case of V+=5V, V-=0V, the data sheet shows that Input Votage Range is Min=1V, Max=3V.
If input volage will be less than 1V or over than 3V, will the device be damaged or not? 
When we use input voltage range 0～5V, how much of voltage for V+=5V, V-=0V should we suply?  

<Question2>
In case of V+=5V, V-=0V, how much of Input Votage Range will be?
If you have the characteristic table which indicates "supply voltage(V+, V-) - Input Voltage Range",
could you let know us?

Kind  regards,

Hirotaka Matsumoto

  • 0
    TI__Guru 52396 points

    Hello Hirotaka,

    No. 0V and 5V will not damage the inputs. Differential Abs Max is ±5V. But the output condition may not be correct at those levels.

    As you saw, the input range limits are (V+) - 2V and (V-) + 1V.  The "Common Mode Limits" graphs show the change over supply and temperature.

    Take a look at the schematic on page 7.

    If the input voltage is below 1V, you pinch-off the input stage current source Q2.

    The input pair (Q1 & Q2) and R1, R2 & R3 need some headroom to function, which accounts for the 2V below V+ requirement.

    There is some chance of the output being correct if the upper common mode limit is violated by one input with the other input within the common mode range since at least one input transistor is still on.

    But violating the lower common mode limit cuts off the current source to the entire input stage, so the output will be indeterminate.

    Is there a particular reason you want to use the LM319? Speed? There are better low-voltage alternatives available. The LM319 is very old device from the 30V days.

    See the LMV7235 (single), TLV3201 (Single), TLV3202 (dual) and TLV3502 (single) for more modern 5V devices..

    Regards,

  • 0 in reply to Paul Grohe
    Guru 27565 points

    Paul san,

    Thank you for your prompt update!

    As you mentioned , "the input range limits are (V+) - 2V and (V-) + 1V", we would like to confirm one point.
    Common Mode Limits of LM319 on P7 datasheet show  (V+) -1.2 and  (V-) + 1V in the worst case.

    So, in case of V+=9V, V-=0V, are  the input range limits (V+) - 1.2V and (V-) + 1V ?(the range from 1V to 7.8V)

    Therefore, in case of VS=±15V,  we guess that  the input range limits are (V+) - 1.2V and (V-) + 1V ?
    (the range from -14V to 13.8V?)

    We need your help.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    Guru 27565 points

    Paul san,

    We guess that you are busy day, but could you reply about our question?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Guru 52396 points

    Hello Hirotaka,

    For ±15V, the table already specifies this as +13V to -13V typical.

    From the LM319 graph, assuming worst case temp operation, then it would be as you surmised; (V+) - 1.2V and (V-) + 1V, or -14 to +13.8V.

    Both the above and the table are typical and are not guaranteed for the LM319. Since it are not tested in production, these points may vary up to 10-20% across devices - so do not design too close to these limits.

    I would suggest using 1.5V from each rail (±13.5V) as a optimistic-conservative design limit.

    If you want guaranteed, then the LM119 and LM219 have guaranteed ±15V limits of 3V from the rails (±12V in). Remember that these limits are for a wider temp range.

    Regards,

  • 0 in reply to Paul Grohe
    Guru 27565 points

    Paul san,

    Thank you for your reply!

    Kind regards,

    Hirotaka Matsumoto