+ Post New Thread
Results 1 to 7 of 7
  1. #1
    Advanced Member level 4
    Points: 6,208, Level: 18
    Achievements:
    7 years registered

    Join Date
    Jan 2012
    Location
    Italy
    Posts
    1,099
    Helped
    41 / 41
    Points
    6,208
    Level
    18

    wide band operational amplifer

    Dear friends,

    I found this cell from analog library of my foundry, it is classified as wide band amplifier,

    my question what the thing makes it wide band, what this architecture named so I can make further research on it

    Thank you

    Best Regards

    Click image for larger version. 

Name:	wideband amp.png 
Views:	12 
Size:	23.2 KB 
ID:	158302

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 3
    Points: 6,121, Level: 18
    Dominik Przyborowski's Avatar
    Join Date
    Jun 2013
    Location
    Norway
    Posts
    785
    Helped
    342 / 342
    Points
    6,121
    Level
    18

    Re: wide band operational amplifer

    It's ordinary Miller OTA working in class A-AB.
    it is wideband because is not narrowband (it is not a joke).
    Don't pay too much attention to names.

    More precisely, this guy is WB because can work from dc to some frequency (maybe several MHz), while narrowband is by definition operating in narrow frequency range (bandpass filter transfer function with 3dB band being small part of center freq), like LC tank LNAs.


    1 members found this post helpful.

  3. #3
    Advanced Member level 3
    Points: 10,657, Level: 24

    Join Date
    Nov 2001
    Location
    US
    Posts
    935
    Helped
    341 / 341
    Points
    10,657
    Level
    24

    Re: wide band operational amplifer

    Not sure how wideband this can be. It is kind of a push-pull amplifier, but apart from that it is just a Miller compensated stage. The UGBW is still gm1/Cm as in regular OTAs. Since the output stage is push-pull, you get gm2=gmp+gmn or some portion of it, which has potentially the ability of pushing the non-dominant pole towards higher frequencies for better phase margin. But I'm not uite sure how well this works because the inputs of the second diff pair connect to points with unequal driving capability/voltage swing.


    1 members found this post helpful.

    •   AltAdvertisement

        
       

  4. #4
    Advanced Member level 4
    Points: 6,208, Level: 18
    Achievements:
    7 years registered

    Join Date
    Jan 2012
    Location
    Italy
    Posts
    1,099
    Helped
    41 / 41
    Points
    6,208
    Level
    18

    Re: wide band operational amplifer

    Dear friends,

    Thank you for your reply,

    I will try to simulate the circuit to see the bandwidth,

    I am not surprised by the name of the circuit more than I didn't understand the structure of the circuit, he used the push pull amplier with starnge connection,

    I see he is using three stage ampliifer, is that have a benifit on the ampliifer bandwidth ?



  5. #5
    Advanced Member level 3
    Points: 10,657, Level: 24

    Join Date
    Nov 2001
    Location
    US
    Posts
    935
    Helped
    341 / 341
    Points
    10,657
    Level
    24

    Re: wide band operational amplifer

    Practically, it is a two stage amplifier. The 1st stage feeds directly the NMOS in the output stage. And the second diff pair has very limited gain, probably in the order of 1, which means it is supposed to have high frequency poles and not really limit the frequency response of the main amplifier.


    1 members found this post helpful.

    •   AltAdvertisement

        
       

  6. #6
    Advanced Member level 4
    Points: 6,208, Level: 18
    Achievements:
    7 years registered

    Join Date
    Jan 2012
    Location
    Italy
    Posts
    1,099
    Helped
    41 / 41
    Points
    6,208
    Level
    18

    Re: wide band operational amplifer

    Dear friends,

    I have simulated the circuit, the result is shown below,

    This cell as I have mentioned before is provided by the foundary, from the simulation result it doesnt looks like it is described as a wide band amplifier, if I increase the bias current it zero will come inside the GBW range,
    and by any way it has zero peak even before 0 dB,

    what is you opinio ?

    Click image for larger version. 

Name:	wb.png 
Views:	5 
Size:	26.8 KB 
ID:	158419



  7. #7
    Advanced Member level 3
    Points: 10,657, Level: 24

    Join Date
    Nov 2001
    Location
    US
    Posts
    935
    Helped
    341 / 341
    Points
    10,657
    Level
    24

    Re: wide band operational amplifer

    Looks OK to me. Enough phase and gain margin, at least in that corner.


    1 members found this post helpful.

--[[ ]]--