The answer to your question was given already in post#10:Hello, What is the meaning of gain -1 stable, gain of +1 stable for an opamp as shown below?
Does it somehow says that the input signal to the opamp needs to connect on plus or minus to the opamp so it will be stable?
Thanks.
Hello Dana, what about filter? do you recommend to plug a filter to the output of the second stage to cancel oscillations and noise?
Thanks.
Klaus - I rather think that the effect of limited slew rate is caused by saturation of the opamps input stage - until the delayed feedback brings the unit back to linear operation. During this very short time of saturation the input stage acts as a current source which loads the Miller capacitance of the second stage (frequency compensation) and, thus, causes this nearly linear signal slope which allows the definition of the slew rate.High dV/dt not only causes problems with the limited output dV/dt, but it may cause the input stage to saturate.
But the filter you posted in another thread only looking for 1 Khz BW ? If so your slew rateHello , I need to amplify sine waves only.square wave test is only to test stability in a lab for closed loop system.
Dana in post 24 suggested that my slew rate is not good at LT1028 that why i switched to AD8034
regarding input capacitance which could cause instability pole.
Is there a way to put some tuning mechanism on the layout that could change input capacitance of the opamp and avoiding it from being unstable?
Thanks.
View attachment 188729
A good ap note on internal versus external slew rate considerations. Attached.Klaus - I rather think that the effect of limited slew rate is caused by saturation of the opamps input stage - until the delayed feedback brings the unit back to linear operation. During this very short time of saturation the input stage acts as a current source which loads the Miller capacitance of the second stage (frequency compensation) and, thus, causes this nearly linear signal slope which allows the definition of the slew rate.
SR correlates with GBW or BW in 1st order partial integrator compensation types like the 741. in small signal BW or large signal with current limits from internal feedback or ext load.For designs with little or no Cload ( OP seems to indicate with no external loading in sim )
slew rate is governed by internal OpAmp considerations :
But to the broader point this covers both internal and external slew considerations :
Regards, Dana.
That torn jacket on the Graeme OA book brings back memories of the late 70's when we each had 2 shelves worth of NSC handbooks and Graeme's book.For designs with little or no Cload ( OP seems to indicate with no external loading in sim )
slew rate is governed by internal OpAmp considerations :
View attachment 188762
But to the broader point this covers both internal and external slew considerations :
Regards, Dana.
--- Updated ---
A good ap note on internal versus external slew rate considerations. Attached.
Excellent foundation book by Graeme, discusses SR extensively, attached.
Regards, Dana.
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