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opa847

Jeff Wang25
Prodigy 200 points

Other Parts Discussed in Thread: OPA847

I run a simulation test of OPA847. The result shows  about 100MHz band width with gain of  -10. the data sheet shows about 600MHZ.  Does have problem in OPA847.TSC model? Attached is design file.opa847_bode.TSC

  • 0
    Prodigy 200 points

    I ran a quick test for the gain of -20 test. The resistor value one case 1k,20K, the other 100, 2k. The bode plot shows the bandwidth very different. Is this voltage feedback amplifier like current feedback, the feedback resistor dictates the bandwidth.

  • 0 in reply to Jeff Wang25
    TI__Genius 12631 points
    Jeff,
    The amplifier is voltage feedback, however you cannot increase the feedback resistance too much because the feedback resistance interacts with the input capacitance of the amplifier to cause a zero in the Noise Gain that then reduces the bandwidth of the amplifier. I would stick with a feedback resistance of close to 750Ohm like the datasheet suggests. Furthermore, please note that the amplifier needs a minimum stable gain of +12V/V, keeping it at 10V/V gain is going to cause instability issues. Even at a gain of 12V/V there is peaking in the frequency response. My recommendation is to use this amplifier in at least a gain of 15V/V to get good time-domain and frequency-domain response characteristics.
    -Samir