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Consider a simple op-amp in a feedback configuration. You can consider the op-amp to be dominant pole compensated and approximated as a first order system.

Let's say that the transient performance (mainly rise time) in response to an input step of the closed-loop system is too slow.

The first option I have is to increase the bandwidth (and drop the gain, maintaining a fixed GBW) and this will make the system faster.

My question is: Will increasing the DC gain help the transient performance? I know it will reduce the BW. But intuitively, it makes sense right, a large gain means the op-amp can react more aggressively in voltage levels to bring itself back to steady-state

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  • \$\begingroup\$ It increases the slew rate up to the amplifier's slew rate but you won't hit your target output value any faster because it is higher too if you increase the gain. \$\endgroup\$
    – DKNguyen
    Aug 4 at 14:16
  • \$\begingroup\$ @DKNguyen sorry, what do you mean that the target is higher too? \$\endgroup\$ Aug 4 at 14:18
  • \$\begingroup\$ If my input is 1, what is the output if my gain is 5 vs 10? You might go twice as fast (up to the slew rate) but you also have twice as far to go \$\endgroup\$
    – DKNguyen
    Aug 4 at 14:18
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    \$\begingroup\$ You are losing the gain, silly. \$\endgroup\$
    – DKNguyen
    Aug 4 at 15:50
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    \$\begingroup\$ Oops. Forgot the whole purpose of the op amp in the first place. \$\endgroup\$ Aug 4 at 15:51

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No, because although your output slope increases (up to the max slew rate) as you increase the closed-loop gain, so too does your output value. You might go twice as fast but you have twice as far to go.

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