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LM124: Missing electrical characteristics

Danilo A.
Mastermind 27180 points
Part Number: LM124
Other Parts Discussed in Thread: LM324B

Hi Team,

We would like to ask your help regarding our customer's inquiry below.

I am looking for additional data on the LM124DG4. I got the datasheet, however it doesn't have the parameters that I am looking for. I am looking for the electrical characteristics for LM124 with Vs =(V+/V-)=5 to 36V, datasheet only have the section for LM124 with Vs=5V. Would like to know the output current( source/sink) and short circuit current for the LM124 with Vs=24V (+/-12V).

Regards,

Danilo

  • 0
    TI__Guru**** 154086 points

    Hello Danilo,

    Most of the specs are 15V; not expecting more current at 24V is fine.

    For Ios, short from OUT to -12V (VCC-) can be too much power, unsafe. Short to ground is supported if sourcing current and Ta=25C

    If sinking current, short to GND or VCC+ is not safe. 

    Avoid shorts if possible. 

    I suggest checking out application note for more details about LM124. Design Guidelines for Devices with LM324/LM358 Cores

  • 0 in reply to Ron Michallick
    TI__Mastermind 27180 points

    Hi Ron,

    Thank you for your response. Please see the feedback of our customer below.

    The datasheet indicates  Vcc =5V in LM124 section.   I am looking for Io, Ios for condition : Vs = +/-12V  ( similar with the section for the LM324B and LM124BA, Vs = (V+) – (V-) = 5v to 36v (+/-2.5v to +/18V)

    My questions are in red.

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Guru**** 154086 points

    Danilo,

    Assuming minimum current is the concern 

    1st red question: Power supply is 15V and 0V. output is 0V, so there is 15V of voltage lost. With a +/-12V supply and a short to 0V, there will be 12V lost on output. Sourcing has an active current limit so +/-12V supply short to 0V should be very close to data sheet values. 

    2nd red question: Power supply is 15V and 0V. output is 15V, so there is 15V of voltage lost. With a +/-12V supply and a short to 0V, there will be 12V lost on output. Sinking is set by the transistor's base current and its beta (current gain) so only a small reduction is current would be expected.

    In both cases, the worst case reduction can be calculated by interpolation; 12/15 = 80% ; although 90% is more reasonable conservative expectation.

    If maximum current was the concern, then a different answer would be needed.

  • 0 in reply to Ron Michallick
    TI__Mastermind 27180 points

    Hi Ron,

    Please see the update from our customer.

    Thank you so much for the information.  

     “ If maximum current was the concern, then a different answer would be needed”

    1. Yes, would like to know the answer for the maximum current
    2. Other questions about the output voltage vs output source/sink current curves
      1. Figure 6-36 : "Output voltage referenced to +Vcc (V)",  is this  (Vcc - Vo) ? Single supply 15V/0V or dual supply +/-15V  are the same ?
      2. Figure 6-35:  this is for single supply?  How about the dual supply ?
      3. Figure 6-37: is there similar one for sinking current limit vs temp?
      4. Would like to know the maximum source and sinking current for dual supply op-amps, example: (1) supply +/-12v, max Io source  @Vo = 2.7V ? (2) supply +/-12v, Max Io sinking @ Vo= - 2.7V?

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Guru**** 154086 points

    Danilo,

    Maximum current in the data sheet electrical tables is 60mA at a 5V voltage loss. At 12V loss sourcing current would be close to 5V and die temperature dependent as seen in figure 6-37. Sinking current short at 12V loss could potential cause device damage. I recommend adding some series resistance between output and short.   

    1a Yes (VCC-Vo) which is voltage loss. This table is accurate for all supply voltages.

    1b Fig 6-25 is Vo - [Vcc-] for dual or single supply. 

    1c No there is not. With increased temperature beta goes up so expect more sinking current which is a harmful trend.   

    1d For sourcing 60mA max at 25C or higher ; for sinking I'd guess the same 60mA (just a guess)

    I suggest adding series resistance so the application has the control over short current instead of making the op amp do it.