This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM124 ESD Protection

Other Parts Discussed in Thread: LM224, LM124, LM139, LM124-N

I've done some searching through the datasheet and I think I have found the answer to the following questions below but I would like a second opinion. The LM124/LM224 does not show ESD diodes for protection in the schematic below, but in the datasheet ESD tolerance is listed as a max of 250V.  Where is this ESD protection from?

1)   Are there any ESD protection diodes or other protective devices on the output connections?

2)   If yes, what are their characteristics?

3)    If no, what is the path that ESD current follows?

 

  • Hello Jeramie,

    The LM124/158 family does NOT have dedicated ESD diodes on any of the pins. This also applies to the LM139/193 comparator family.

    Positive currents will flow through the device itself, and the negative currents will flow through the substrate diode. This is all mentioned in notes 6 and 10 of the LM124 datasheet.

    This is why the ESD ratings are lower than current parts.

    The process is old enough that the structures are large enough to handle the currents. ESD was not a big issue during the Nixon administration, so most of the bipolar devices from the 1970's do not have dedicated ESD diodes (though they may have input clamps).

    If large transients are expected, external clamp diodes to the supplies should be used. Continuously hammering the devices will eventually cause damage to the devices.

    A similar question was answered in a previous thread. See:

      http://e2e.ti.com/support/amplifiers/precision_amplifiers/f/14/t/160419.aspx#583177

    Regards,

    Paul Grohe

    SVA Precision Applications

  • Hello, I have two questions, first, is the quiescent current of LM124 the sum of four current source, i.e. 160uA? (with quiescent current  i mean the current with NO load) and second what is the source and sink current, if Vcc =12 V and Vee=-5V and the Load is 1 ohm, what is the source and sink current? I am very confuse with that... Thank you very much.

  • Hello Dimitris,

    The quiescent current is typically 1.4mA for ALL four amplifiers combined (or 350uA per amplifier).

    One ohm is much too large of a load. it will never be able to drive that.

    The sinking and sourcing capability is shown in the Output Sinking/Sourcing graphs (Figs 1 & 2 for LM124 datasheet, Figs 10 and 11 for LM124-N datasheet).

    The graphs show the output voltage as a delta from the rail. The more current, the farther from the rail the output will swing.

    If you were to sink 1mA, the output would only swing to about 0.7V above VEE.

    If you were to source 1mA, the output would only swing to within 1.2V of VCC. Note that the LM124 is not a R-R output and does not completely swing to VCC.

    So at VCC=+12V, sourcing 1mA, you would swing to +10.8V (+12V-1.2V).

    With a -5V VEE, sinking 1mA, you would swing to -4.3V (-5V + 0.7) .

    I'm note sure where the 160uA comes from...is that your expected load?

    Regards,
  • Dear Paul,

    thanks for your response.

    The  quiescent current (350uA) always exist, I mean this current flows in all conditions, independently of power supplies, so i have to summarize to Icc if I want to compute the needed power from the source? 

    I thought the Iq was the sum from four current source that shown in schematic on datasheet. 

    This site ("www.ti.com/.../LM124") refers that the Iq per channel is 0.175mA, is this the quiescent current, because I did not find the number (1.4mA) you said me.

    Thanks in advance,

    Dimitris 

  • Dimitris,

    It is here in data sheet