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Original question:

THS3491: Pspice for TI Simulation Issue

THS3491: unity-gain stable

Hanno Reimer
Intellectual 1670 points
Part Number: THS3491
Other Parts Discussed in Thread: THS3091

is the THS3491 unity-gain stable?

Or is there a better amp for that purpose? 

Thanks and bye 
Hanno

  • 0
    TI__Expert 6050 points

    Hi Hanno,

    The THS3491 is not a unity-gain stable amplifier. The THS3091 is a current feedback amplifier that has similar performance, including the higher supply voltage range, that can operate in a unity-gain configuration. 

    If there are specific performance specs that you need for your application that the THS3091 does not meet, please let me know and I can recommend another part that meets those specs closer.

    Thanks,

    Nick

  • 0
    Guru 48395 points

    Well Hanno, 

    This table shows the suggested Rf vs gain for the 2 packages, the DDA has much higher bond wire inductance interacting with the loop phase margin, this went down to a gain of 2, but I would guess gain of 1 in the RGT would be stable for about 1.2kohm Rf, the sims will show what you need. I sort of set up the THS3491 definition assuming some gain since if you can produce an input signal with its slew rate for a unity gain case, why use the amplifier - hence the input headroom was relatively high to use a design giving better CMRR.