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OPA2990: I am designing am amplifier for the DRV425 sensor

Part Number: OPA2990

 I am curious about ESD. Are the CMOS op amps more susceptible than the older Bipolar op amps? For example the OP275G (actually that one has a JFET front end).

  • Hi Quentin,

    most of the older FET-OPAmps had no ESD protection at the inputs at all and were very suscetible to ESD. Todays CMOS OPAmps always have them and although the modern CMOS OPAmps have way smaller structures on the die, they can usually withstand higher ESD because of the internally added ESD protection.

    Nevertheless, since real world ESD can easily exceed 8kV HBM, adding external ESD protection like TVS, clamping diodes and/or low pass filtering caps is a good design practise when the inputs or outputs can come in direct contact with the environment. External ESD protection should be located close to the points where the signal enters or leaves the board and should be shunted to the metal enclosure either directly or by the help of an Y-cap. ESD should never be allowed to enter the circuit and travel across the board. Using a solid ground plane, proper decoupling caps directly at the OPAmps and the use of shielded cables with the shield 360° bonded to the metal enclosure are also recommended. To avoid ESD from travelling across the board, the cables should not sit at opposite edges of the board. Also, it's a good idea to move the OPAmps in question a bit away from the signal entry point of board in order to isolate them from the high ESD currents and by this to avoid "secondary ESD" issues. 

    It has been reported many times that particularily in situations with non-ideal ESD protection measures (absence of metal enclosure and such things...) taking an OPAmp with a higher ESD rating can indeed help to avoid ESD issues.


  • Hello Quentin, 

    Welcome to e2e!

    This is discussed on section 7.3.7 of the datasheet (including the TVS diodes Kai has mentioned above). 

    All the best,