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Questions of LM138

Takahiro Nishizawa
Genius 5575 points
Other Parts Discussed in Thread: LM138

We have questions about LM138.

Question 1.

In datasheet p.12,  8.2.1.1 "Design Requirements",

Vout=1.25V(1+R2/R1)+Iadj(R2)

Please tell us the method to calculate Iadj(R2).

Question 2.

Output voltage is 5V.

What kind of parameters will it affect in voltage variation.



Best regards,


Takahiro Nishizawa
  • 0
    TI__Mastermind 21965 points
    Hey Takahiro-san,

    Question 1:
    Iadj is specified in the datasheet to be 45 uA typical and 100 uA maximum.
    Iadj(R2) is Iadj*R2.

    Q2:
    There are many parameters that effect voltage variation:
    Load Regulation
    Line Regulation
    Reference Voltage Variation
    ADJ pin current change
    Temperature Stability
    Resistor Tolerance

    Thanks,
    Daniel