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LM338: Interfacing with LM308 Op Amp

Donald Livesay
Prodigy 20 points
Part Number: LM338

  Having a person run through hoops just to get a question answered is just ridiculous.

On the data sheet provided by your company on LM338T/NOPB figure 42. Adjustable 15-A Regulator,  in the middle of the circuit you show a trace from the third LM338 to pin 7 of an LM308. the LM308 is a 16 volt IC and the output of the LM338 is to 25 volts in this circuit so will that not fry the LM308 giving it 24 volts. is this a mistake or am i just missing something here. can i replace this IC with a 36 volt op amp instead.
also you show no protection of any kind in this circuit as you do in others,  can you please explain why you omitted your own safety precautions in this circuit and where and how can i implement them or are they needed.

Request# 1-3894386033

[THREAD ID: 1-1SEM8BD]

[SR THREAD ID: 1-1SEM7HT]

  • 0
    TI__Guru 55940 points
    Hi Donald,

    I apologize if you have been directed multiple places while trying to find an answer to your question. For your knowledge, the E2E forums (where you are now) is the best place to start for TI support.

    The LM308 was a +/1 18 V device sold by National Semiconductor (now TI). Several companies have a similar device by the same name that may have a lower voltage rating, but National assumed that a customer using their LDO would also want to use their LM308 amp. Since the negative rail is tied to GND, the positive rail can be connected to 36 V (2 x 18).

    The example given in Figure 42 of the LM338 datasheet is meant to help give a starting point for a customer on their specific application design. Every application will vary; therefore, we do not provide every detail in the design but rather enough to communicate a design concept. You are welcome to use whatever amp that satisfies your application requirements.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 20 points
    It was a hassle getting here but the end result was good. i do thank you for the very informative answer and thus i will implement safety precautions according to the general guidelines provided and op amp of choice.