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OPA2340: signal input terminals absolute maximum rating with no power supply voltage

Kai Nomiyama
Expert 5285 points
Part Number: OPA2340

Hi Opamps team,

I have a question about OPA2340 signal input terminals abso max rating.

Datasheet mentions voltage/signal input terminals is -0.5V_min to 0.5V_max(this should be GND-0.5V and Vs+0.5V).
when there is no power supply for Vs(Vs=0V), what is the abso max voltage/signal input terminals? still -0.5V_min to 0.5V_max(this should be GND-0.5V and Vs+0.5V)?

Use-case
input signal is coming with no Vs(Vs=0V) and then Vs is supplied to V+.

Regards,
Kai

  • 0
    Guru 140200 points

    Hi Kai,

    the given values are valid for all supply voltages, even if there's no power supply.

    It's not wise to apply an input voltage while an OPAmp is unpowered. This can cause trouble during power up. I would try to clamp the input voltage to the rails by the help of protection diodes. Between the protection diodes and the input of OPA2340 I would insert a current limiting resistor to limit the residual input current to under 1mA. The protection diodes can be Schottkys. But then you will suffer from a huge leakage current. Or you can use the BAV99 or even BAV199 (low leakage diode). If the voltage drop across the protection diodes exceeds 0.5V, I would use a voltage divider instead of single current limiting resistor. Also, think about connecting a TVS from the supply pin of OPA2340 to signal ground.

    It's best to avoid applying an input voltage while the supply voltage is down.

    Kai