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The INA143 difference amplifier datasheet states that the device supports G=10 and G=0.1 when connected in difference amplifier configuration. However, the datasheet only gives specifications for the G=10 case.

The bandwidth there is given as 0.15MHz for the G=10 case (where the internal op amp will see a gain of 11), but I'm interested in the bandwith at G=0.1 (where the op amp's gain is 1.1). Given that op amps typically have a 20db/decade gain/frequency relation, can I extrapolate that the bandwidth in the G=0.1 configuration will likely be around 1MHz or above?

I plan to use the amplifier inside a feedback loop, so good bandwidth will be essential for stability.

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    \$\begingroup\$ It doesn't look like they say. \$\endgroup\$
    – Andy aka
    Commented Feb 10, 2015 at 12:32
  • \$\begingroup\$ Is your application cost sensitive? For a few dollars more there are faster instrumentation amps. \$\endgroup\$
    – George Herold
    Commented Feb 10, 2015 at 15:03
  • \$\begingroup\$ It's not particularly cost-sensitive. \$\endgroup\$
    – Medo42
    Commented Feb 10, 2015 at 15:09
  • \$\begingroup\$ One thing to look out for though is that the input voltage is up to +-30V on the positive input. With the default three amplifier configuration, the in-amp would have to run from +-30V supplies. It seems far easier to find diff-amps which support that range, since they divide the voltage down before it reaches an amp. \$\endgroup\$
    – Medo42
    Commented Feb 10, 2015 at 15:14

2 Answers 2

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I would expect the gain-bandwidth product to be a constant, but it's worth comparing the two on the bench before designing it in (I suggest measuring both the gain-of-10 -3dB point and the gain-of-0.1 -3dB point to have a point of comparison with the datasheet limits).

Note that the slew rate is typically a fairly good 5V/us, but you'll run into that at high amplitudes.

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  • \$\begingroup\$ Thanks for the answer. The slew rate doesn't limit me here, because the controlling amplifier itself is pretty slow. 0.5V/µs would probably be enough already. \$\endgroup\$
    – Medo42
    Commented Feb 10, 2015 at 15:08
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I suppose the opamps are unity-gain compensated. Therefore, it is logical to assume that the closed-loop bandwidth in case of G=0.1 will be app. 10 times larger that for G=10. To be somewhat conservative, I would expect 1.2...1.5 MHz.

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  • \$\begingroup\$ The op-amp inside the diff-amp doesn't actually see a gain below 1 in the G=0.1 diff-amp configuration. \$\endgroup\$
    – Medo42
    Commented Feb 10, 2015 at 15:54
  • \$\begingroup\$ Ohh - it seems that there was something like a "short" in my brain. Yes - it`s nearly a unity gain configuration. Thank you for correcting me. I will edit my answer correspondingly. \$\endgroup\$
    – LvW
    Commented Feb 10, 2015 at 16:42

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