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Original question:

TL074: Input tolerant function opamp

TL054: Protecting Op Amp Inputs Driven Outside Power Supply Rails

David Westmoreland
Prodigy 10 points
Part Number: TL054
Other Parts Discussed in Thread: TL084, TL084H,

The "TL05x, TL05xA datasheet (Rev. A)" in the "absolute maximum ratings..." section includes Note 3 "The magnitude of the input voltage must never exceed the magnitude of the supply voltage or 15 V, whichever is less" and also includes a specification for "Input current, II (each input) " of +/-1mA.  What can happen to the op amp if the magnitude of the input voltage exceeds the supplies but is clamped to limit the current so it never exceeds +/-1mA either when the supplies are power cycling or when they have reached their steady-state values? 

The TL084 also includes the same note "The magnitude of the input voltage must never exceed the magnitude of the supply voltage...", but does not include a maximum input current specification (but TL084H does include a note that "Input pins are diode-clamped to the power-supply rails. Input signals that may swing more than 0.5 V beyond the supply rails must be
current limited to 10 mA or less."). 

What can happen to the TL08x-non-H-suffixed devices if the input Voltage exceeds the supply voltage even if the current is limited to +/-1mA?  Would the internal ESD-protection circuitry divert the current to protect the op amp?

  • 0
    TI__Mastermind 22361 points

    Hey David,

    For the TL084H, the 10mA value is a rule of thumb safe input current that the ESD diodes can handle before damage. This is something that should be a temporary value and not over a long period of time.

    For TL054, you can see in the datasheet that there are no ESD diodes on the input/output of the op amp. The recommendation would be external clamping diodes to V+/V- to protect the inputs of the op amp.

    Best,
    Jerry