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| promach:
For the Improvements_in_biasing_and_compensation_of_CMOS_opamp (second reference link), why the author break open the connection between gates of M3A and M3B ? And how to derive the inequality expression (14) in the document ? |
| Wimberleytech:
--- Quote from: promach on April 16, 2019, 10:32:15 am ---For the Improvements_in_biasing_and_compensation_of_CMOS_opamp (second reference link), why the author break open the connection between gates of M3A and M3B ? And how to derive the inequality expression (14) in the document ? --- End quote --- Set P3 < P1 and simply do the algebra. Eq 14 appears to have an error...should be gm2b in numerator, not gm2a |
| promach:
--- Quote ---Set P3 < P1 and simply do the algebra. Eq 14 appears to have an error...should be gm2b in numerator, not gm2a --- End quote --- I will check your advice regarding the inequality expression, but why set P3 < P1 ? Is it dominant pole compensation or something else ? I try to incorporate the author schematics (Figure 6 in the second reference link) into the opamp, but it resulted in erroneous bode plot Which part is wrong in the schematics ? |
| Wimberleytech:
--- Quote from: promach on April 17, 2019, 03:00:49 am --- --- Quote ---Set P3 < P1 and simply do the algebra. Eq 14 appears to have an error...should be gm2b in numerator, not gm2a --- End quote --- I will check your advice regarding the inequality expression, but why set P3 < P1 ? Is it dominant pole compensation or something else ? --- End quote --- yes, essentially --- Quote --- I try to incorporate the author schematics (Figure 6 in the second reference link) into the opamp, but it resulted in erroneous bode plot Which part is wrong in the schematics ? --- End quote --- ALWAYS check bias points before even looking at your ac response. In this case, your biasing is broken. |
| promach:
See the following circuit : I am having problem using the miller lead compensation (M24 mosfet in triode region) Any help ? When I saw this 90MHz bandwidth opamp OPA838, I am inspired to do the same, but my current circuit bandwidth is only 10MHz. |
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