OPA1632: What is the recommended input protection scheme for OPA1632?

Brian Josephs

Part Number: OPA1632

I'm running the amplifier on +/-5vDC. I'm looking for recommendations on how to protect the inputs as this device will be connected to the outside world. Is it sufficient to clamp input signals to the voltage rails with silicon diodes or should I try to limit the signal to below the common mode limits? How does the device behave when the max common mode or differential signals are exceeded?

over 6 years ago

0 Brian Josephs over 6 years ago

Prodigy 90 points

I could really use some help here. The data sheet indicates that the pins are protected against ESD but I see nothing about max current. If the max common mode is exceeded will the device be damaged?

0 Per-Anders Sjöström over 6 years ago in reply to Brian Josephs

Prodigy 250 points

www.ti.com/.../sszb130b.pdf maybe you can find something here?

0 Keyur Tejani over 6 years ago in reply to Brian Josephs

TI__Intellectual 870 points

As you mentioned, OPA1632 has input protection diodes. These diodes can typically take up to 10mA of current so to protect the inputs, you want to use current limiting resistors that ensure less than 10mA in to the inputs.

As far as voltage goes, input voltages should not exceed ±Vs and Vdiff should not exceed ±3V.

Thanks,

Keyur

0 Per-Anders Sjöström over 6 years ago in reply to Keyur Tejani

Prodigy 250 points

Google with "esd protection differential amplifier" and show pictures can give you some inspiration.

0 Brian Josephs over 6 years ago in reply to Per-Anders Sjöström

Prodigy 90 points

Per-Anders, thanks for the link.

0 Brian Josephs over 6 years ago in reply to Keyur Tejani

Prodigy 90 points

Keyur,

Do you know if there could be damage if the common mode limits are exceeded? From the datasheet:

Input Voltage
Common-Mode Input Range (V−) + 1.5 (V+) − 1 V

I don't expect this to be violated by normal operation, but should a fault put large and similar voltage on both input pins, could damage result?

0 Keyur Tejani over 6 years ago in reply to Brian Josephs

TI__Intellectual 870 points

Brian,

Exceeding the Vcmir spec will not damage the device. The main effect of going beyond the Vcmir spec (and as long as below ±Vs) is that the Vos will increase beyond what corresponds to the CMRR spec.

Thanks,
Keyur

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OPA1632: What is the recommended input protection scheme for OPA1632?