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ADA4096 not clamping input in unity gain buffer test circuit

I'm testing the ADA4096-2 amplifier. The testing circuit is an unity gain buffer with a 30Hz sine signal, with dual +/- 3V supply, both amplifiers receive the same signal. I see the output is clamped correctly to the supply voltage values, however, as I increase the amplitude of the signal (>4V above the positive rail), the positive clamping starts to fail and the voltage in the positive power supply rail starts to raise. I'm attaching the image of the test circuit and the signals we are seeing (the red trace is the source signal, the yellow one is the amplifier output).

Am I doing anything wrong? I expected the clamping to work up to 32 V above and below the power rails and not to affect the power rails at all.

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  • FormerMember
    0 FormerMember

Mario,

  Are you talking about the output voltage rising or the power supply rail rising?

See fig 54 and 55 in the d.s.  Some slight Vout rise is normal, but if your +3V supply

rail is rising, you don't have a stiff enough supply or one that can only source current

and not sink current.  When the input voltage is high, the current gets shunted to

the rails;  see fig 53.

Harry

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  • FormerMember
    0 FormerMember

Mario,

  Are you talking about the output voltage rising or the power supply rail rising?

See fig 54 and 55 in the d.s.  Some slight Vout rise is normal, but if your +3V supply

rail is rising, you don't have a stiff enough supply or one that can only source current

and not sink current.  When the input voltage is high, the current gets shunted to

the rails;  see fig 53.

Harry

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