Telescopic op amp simulation problem

Discussion in 'Homework Help' started by aliloooz, Jun 16, 2009.

  1. aliloooz

    Thread Starter New Member

    Jun 16, 2009
    1
    0
    Good day everybody,

    I'm using National Instrument's Multisim 10 to design and simulate a fully differntial telescopic op amp. The design picture, Problem source, design details and simulation files are associated.

    The problem is that I can't get the NMOS telesdcopic transistors to work in saturation, the entire biasing voltage is distributed on the PMOS transistors.

    Plz help if anybody knows where's the problem.






    Design details


    Currents in P, NMOS current mirrors are 0.17 mA each. Currents in differential branches are 1.5 mA each.


    Mb2: (PMOS current mirror – 2N6804)
    L=1u W=118.5u
    * RS=0 RD=0 LD=0 CBD=0 CBS=0 CGBO=0
    .MODEL MM PMOS LEVEL=1 IS=1e-32
    +VTO=-0.7 LAMBDA=0.1KP=3.555m
    +CGSO=3.44747e-06 CGDO=1e-11
    .

    M5-7 (PMOS telescopic – 2N6804)
    M1 9 7 8 8 MM L=1u W=1111u
    * RS=0 RD=0 LD=0 CBD=0 CBS=0 CGBO=0
    .MODEL MM PMOS LEVEL=1 IS=1e-32
    +VTO=-0.7 LAMBDA=0.1KP=33.33m
    +CGSO=3.44747e-06 CGDO=1e-11

    M1-4: (NMOS telescopic – 2N7000)
    Cgs 2 3 12.3E-12
    Cgd1 2 4 27.4E-12
    Cgd2 1 4 6E-12
    M1 1 2 3 3 MOST1 W=2.5m L=2u
    M2 4 2 1 3 MOST2 W=2.5m L=2u
    D1 3 1 Dbody
    .MODEL MOST1 NMOS(Level=3 Kp=75m W=2.5m L=2u Rs=20m Vto=0.7 Rd=1.186)
    .MODEL MOST2 NMOS(VTO=-0.7 Kp=75m W=2.5m L=2u Rs=20m)
    .MODEL Dbody D(Is=125f N=1.023 Rs=1.281 Ikf=18.01 Cjo=46.3p M=.3423
    + Vj=.4519 Bv=60 Ibv=10u Tt=161.6n)


    M9: (current source NMOS – 2N7000)
    Cgs 2 3 12.3E-12
    Cgd1 2 4 27.4E-12
    Cgd2 1 4 6E-12
    M1 1 2 3 3 MOST1 W=0.8m L=2u
    M2 4 2 1 3 MOST2 W=0.8m L=2u
    D1 3 1 Dbody
    .MODEL MOST1 NMOS(Level=3 Kp=24m W=0.8m L=2u Rs=20m Vto=0.7 Rd=1.186)
    .MODEL MOST2 NMOS(VTO=-0.7 Kp=24m W=0.8m L=2u Rs=20m)
    .MODEL Dbody D(Is=125f N=1.023 Rs=1.281 Ikf=18.01 Cjo=46.3p M=.3423
    + Vj=.4519 Bv=60 Ibv=10u Tt=161.6n)



    Mb1: (NMOS current mirror – 2N7000)
    Cgs 2 3 12.3E-12
    Cgd1 2 4 27.4E-12
    Cgd2 1 4 6E-12
    M1 1 2 3 3 MOST1 W=45.33u L=2u
    M2 4 2 1 3 MOST2 W=45.33u L=2u
    D1 3 1 Dbody
    .MODEL MOST1 NMOS(Level=3 Kp=1.36m W=45.33u L=2u Rs=20m Vto=0.7 Rd=1.186)
    .MODEL MOST2 NMOS(VTO=-0.7 Kp=1.36m W=45.33u L=2u Rs=20m)
    .MODEL Dbody D(Is=125f N=1.023 Rs=1.281 Ikf=18.01 Cjo=46.3p M=.3423
    + Vj=.4519 Bv=60 Ibv=10u Tt=161.6n)
     
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