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OPA2210: Phase reversal

Thomas Larsen
Prodigy 80 points

Part Number: OPA2210
Other Parts Discussed in Thread: OPA2192, OPA2986

Hi

I have made a simulation using OPAx210.LIB, where it seems like the opamp makes phase reversal if the inputs gets more that 680mV apart. In unity gain configuration, with 10K from output to negative input, driving it with a sawtooth at 10Hz, rail to rail, 0V to +12V.

I understand that the signal shall be clipped, because it is not a rail to rail input opamp, but it states in the datasheet that it does not make phase reversal, but somehow the simulation shows phase reversal.

Can you explain what happens?

 

Br Thomas 

  • 0
    TI__Expert 8200 points

    Hi Thomas,

    The OPA2210 has differential input protection for high input signals, which is clamping the amplifier and causing the error you are seeing. 680mV is very close to the typical diode drop value of 0.7V, which is when the clamping occurs. This differential input protection can be seen in the functional block diagram of the amplifier in Section 7.2 of the datasheet (see below).

    These back-to-back input diodes are common in bipolar amplifiers, as they help to protection against Vbe breakdown of the input transistors. 

    You can also determine the type of ESD protection an amplifier has by looking at the Absolute Maximum Ratings table of the datasheet. From the below image, we can see that the input differential voltage must not exceed 1V.

    For details on ESD Cells in Op Amps, please see the application note HERE. I discuss the different types of ESD protection amplifiers have, as well as how to best protect an amplifier from ESD and EOS. 

    For an amplifier with similar performance to the OPA2210, but without the back-to-back diodes, please consider the OPA2192 or OPA2986. The OPA2986 is available for sampling right now, and has increased power supply range compared to the OPA2210 and OPA2192. The gain bandwidth of both devices is lower, but all other specifications are very similar. I have provided a high level comparison table below.

    Please let me know if you have further questions.

    Best regards,
    Carrie