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Finding transconductance/gm in BSIM4 model.

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ehsanaiman

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Hello,

Im doing calculation for determining W/L ratio in OTA. So, I need some parameters from BSIM4 model MOSFET such as threshold voltage and transconductance.
This is BSIM4 model I get from simulation netlist i think;
Code:
Model Name: n12.1  
 BSIM4 Model (Level 54)
    MOBMOD = 0
    BINUNIT = 1
    PARAMCHK = 1
    CAPMOD = 2
    DIOMOD = 1
    RDSMOD = 0
    TRNQSMOD = 0
    ACNQSMOD = 0
    RBODYMOD = 1
    RGATEMOD = 1
    PERMOD = 1
    GEOMOD = 1
    RGEOMOD = 0
    FNOIMOD = 1
    TNOIMOD = 0
    IGCMOD = 1
    IGBMOD = 1
    STIMOD = 0
    VERSION =      4 
    TOXREF = 2.05e-09 
    TOXE = 2.05e-09 
    TOXP = 1.4e-09 
    TOXM = 2.05e-09 
    DTOX = 6.5e-10 
    EPSROX =    3.9 
    CDSC = 0.0002 
    CDSCB =      0 
    CDSCD =      0 
    CIT =      0 
    NFACTOR =    1.7 
    XJ = 2.8e-08 
    VSAT = 1.138e+05 
    A0 =      1 
    AGS =  1e-20 
    A1 =      0 
    A2 =      1 
    AT = 3.3e+04 
    KETA =   0.04 
    NSUB =  6e+16 
    NDEP = 1.94e+18 
    NSD =  2e+20 
    NGATE =  2e+20 
    GAMMA1 =      0 
    GAMMA2 =      0 
    VBX =      0 
    VBM =     -3 
    XT = 1.55e-07 
    K1 =    0.4 
    KT1 =  -0.11 
    KT1L =      0 
    KT2 =  0.022 
    K2 =   0.01 
    K3 =      0 
    K3B =      0 
    LPE0 =      0 
    LPEB =      0 
    DVTP0 = 1.2e-09 
    DVTP1 =    0.1 
    W0 = 2.5e-06 
    DVT0 =      1 
    DVT1 =      2 
    DVT2 = -0.032 
    DVT0W =      0 
    DVT1W =      0 
    DVT2W =      0 
    DROUT =    0.5 
    DSUB =    0.1 
    VTH0 =  0.397 
    EU =   1.67 
    UA =  6e-10 
    UA1 = 4.31e-09 
    UB = 1.2e-18 
    UB1 = 7.61e-18 
    UC = -3e-11 
    UC1 = -5.6e-11 
    U0 = 0.0547 
    UTE =   -1.5 
    VOFF =  -0.13 
    VOFFL =      0 
    MINV =   0.05 
    FPROUT =    0.2 
    PDITS =   0.08 
    PDITSD =   0.23 
    PDITSL = 2.3e+06 
    DELTA =   0.01 
    RDSW =    180 
    RDSWMIN =      0 
    RDWMIN =      0 
    RSWMIN =      0 
    RDW =     90 
    RSW =     90 
    PRWG =      0 
    PRWB = 6.8e-11 
    PRT =      0 
    ETA0 = 0.0074 
    ETAB =      0 
    PCLM =   0.06 
    PDIBLC1 =  0.001 
    PDIBLC2 =  0.001 
    PDIBLCB = -0.005 
    PSCBE1 = 8.14e+08 
    PSCBE2 =  1e-07 
    PVAG =  1e-20 
    WR =      1 
    DWG =      0 
    DWB =      0 
    XW =      0 
    XWREF =      0 
    XL = -4e-08 
    XLREF = -4e-08 
    B0 = -1e-20 
    B1 =      0 
    ALPHA0 =  0.074 
    ALPHA1 =  0.005 
    AGIDL = 0.0002 
    BGIDL = 2.1e+09 
    CGIDL = 0.0002 
    PHIN =      0 
    EGIDL =    0.8 
    AIGC =  0.012 
    BIGC = 0.0028 
    CIGC =  0.002 
    AIGSD =  0.012 
    BIGSD = 0.0028 
    CIGSD =  0.002 
    AIGBACC =  0.012 
    BIGBACC = 0.0028 
    CIGBACC =  0.002 
    AIGBINV =  0.014 
    BIGBINV =  0.004 
    CIGBINV =  0.004 
    NIGC =      1 
    NIGBINV =      3 
    NIGBACC =      1 
    NTOX =      1 
    EIGBINV =    1.1 
    PIGCD =      1 
    POXEDGE =      1 
    XRCRG1 =     12 
    TNOIA =    1.5 
    TNOIB =    3.5 
    NTNOI =      1 
    XRCRG2 =      5 
    BETA0 =     30 
    IJTHDFWD =   0.01 
    IJTHSFWD =   0.01 
    IJTHDREV =  0.001 
    IJTHSREV =  0.001 
    XJBVD =      1 
    XJBVS =      1 
    BVD =     10 
    BVS =     10 
    VFB =  -0.55 
    GBMIN =  1e-10 
    RBDB =     15 
    RBPB =      5 
    RBSB =     15 
    RBPS =     15 
    RBPD =     15 
    CGSL = 2.653e-10 
    CGDL = 2.653e-10 
    CKAPPAS =   0.03 
    CKAPPAD =   0.03 
    CF = 1.16e-10 
    CLC =  1e-07 
    CLE =    0.6 
    DWC =  5e-09 
    DLC = 7.5e-09 
    DLCIG = 7.5e-09 
    DWJ =      0 
    VFBCV =     -1 
    ACDE =      1 
    MOIN =     15 
    NOFF =    0.9 
    VOFFCV =   0.02 
    DMCG =      0 
    DMCI =      0 
    DMDG =      0 
    DMCGT =      0 
    XGW =      0 
    XGL =      0 
    RSHG =    0.4 
    NGCON =      1 
    TCJ =  0.001 
    TPB =  0.005 
    TCJSW =  0.001 
    TPBSW =  0.005 
    TCJSWG =  0.001 
    TPBSWG =  0.005 
    SK0 =      0 
    SK1 =      0 
    SK2 =      0 
    SL =  2e-06 
    SW =  2e-06 
    K =      0 
    TNOM =  300.1 
    CGSO = 1.9e-10 
    CGDO = 1.9e-10 
    CGBO = 2.56e-11 
    XPART =      0 
    RSH =      5 
    JSS = 0.0001 
    JSWS =  1e-11 
    JSWGS =  1e-10 
    PBS =      1 
    MJS =    0.5 
    PBSWS =      1 
    MJSWS =   0.33 
    CJS = 0.0005 
    CJSWS =  5e-10 
    NJS =      1 
    PBSWGS =      1 
    MJSWGS =   0.33 
    CJSWGS =  3e-10 
    XTIS =      3 
    JSD = 0.0001 
    JSWD =  1e-11 
    JSWGD =  1e-10 
    PBD =      1 
    MJD =    0.5 
    PBSWD =      1 
    MJSWD =   0.33 
    CJD = 0.0005 
    CJSWD =  5e-10 
    NJD =      1 
    PBSWGD =      1 
    MJSWGD =   0.33 
    CJSWGD =  5e-10 
    XTID =      3 
    LMLT =      1 
    WMLT =      1 
    LINT = 7.5e-09 
    LL =      0 
    LLC =      0 
    LLN =      1 
    LW =      0 
    LWC =      0 
    LWN =      1 
    LWL =      0 
    LWLC =      0 
    LMIN =  1e-07 
    LMAX =  2e-05 
    WINT =  5e-09 
    WL =      0 
    WLC =      0 
    WLN =      1 
    WW =      0 
    WWC =      0 
    WWN =      1 
    WWL =      0 
    WWLC =      0 
    WMIN = 1.2e-07 
    WMAX = 0.0009 
    NOIA = 6.25e+41 
    NOIB = 3.125e+26 
    NOIC = 8.75e+09 
    EM = 4.1e+07 
    EF =      1 
    AF =      1 
    KF =      0 
    TRS =      0 
    TRD =      0

Which of these parameters is transconductance value?

Thank you.
 

Hello,

Im doing calculation for determining W/L ratio in OTA. So, I need some parameters from BSIM4 model MOSFET such as threshold voltage and transconductance.
This is BSIM4 model I get from simulation netlist i think;
Code:
Model Name: n12.1  
 BSIM4 Model (Level 54)
    MOBMOD = 0
    BINUNIT = 1
    PARAMCHK = 1
    CAPMOD = 2
    DIOMOD = 1
    RDSMOD = 0
    TRNQSMOD = 0
    ACNQSMOD = 0
    RBODYMOD = 1
    RGATEMOD = 1
    PERMOD = 1
    GEOMOD = 1
    RGEOMOD = 0
    FNOIMOD = 1
    TNOIMOD = 0
    IGCMOD = 1
    IGBMOD = 1
    STIMOD = 0
    VERSION =      4 
    TOXREF = 2.05e-09 
    TOXE = 2.05e-09 
    TOXP = 1.4e-09 
    TOXM = 2.05e-09 
    DTOX = 6.5e-10 
    EPSROX =    3.9 
    CDSC = 0.0002 
    CDSCB =      0 
    CDSCD =      0 
    CIT =      0 
    NFACTOR =    1.7 
    XJ = 2.8e-08 
    VSAT = 1.138e+05 
    A0 =      1 
    AGS =  1e-20 
    A1 =      0 
    A2 =      1 
    AT = 3.3e+04 
    KETA =   0.04 
    NSUB =  6e+16 
    NDEP = 1.94e+18 
    NSD =  2e+20 
    NGATE =  2e+20 
    GAMMA1 =      0 
    GAMMA2 =      0 
    VBX =      0 
    VBM =     -3 
    XT = 1.55e-07 
    K1 =    0.4 
    KT1 =  -0.11 
    KT1L =      0 
    KT2 =  0.022 
    K2 =   0.01 
    K3 =      0 
    K3B =      0 
    LPE0 =      0 
    LPEB =      0 
    DVTP0 = 1.2e-09 
    DVTP1 =    0.1 
    W0 = 2.5e-06 
    DVT0 =      1 
    DVT1 =      2 
    DVT2 = -0.032 
    DVT0W =      0 
    DVT1W =      0 
    DVT2W =      0 
    DROUT =    0.5 
    DSUB =    0.1 
    VTH0 =  0.397 
    EU =   1.67 
    UA =  6e-10 
    UA1 = 4.31e-09 
    UB = 1.2e-18 
    UB1 = 7.61e-18 
    UC = -3e-11 
    UC1 = -5.6e-11 
    U0 = 0.0547 
    UTE =   -1.5 
    VOFF =  -0.13 
    VOFFL =      0 
    MINV =   0.05 
    FPROUT =    0.2 
    PDITS =   0.08 
    PDITSD =   0.23 
    PDITSL = 2.3e+06 
    DELTA =   0.01 
    RDSW =    180 
    RDSWMIN =      0 
    RDWMIN =      0 
    RSWMIN =      0 
    RDW =     90 
    RSW =     90 
    PRWG =      0 
    PRWB = 6.8e-11 
    PRT =      0 
    ETA0 = 0.0074 
    ETAB =      0 
    PCLM =   0.06 
    PDIBLC1 =  0.001 
    PDIBLC2 =  0.001 
    PDIBLCB = -0.005 
    PSCBE1 = 8.14e+08 
    PSCBE2 =  1e-07 
    PVAG =  1e-20 
    WR =      1 
    DWG =      0 
    DWB =      0 
    XW =      0 
    XWREF =      0 
    XL = -4e-08 
    XLREF = -4e-08 
    B0 = -1e-20 
    B1 =      0 
    ALPHA0 =  0.074 
    ALPHA1 =  0.005 
    AGIDL = 0.0002 
    BGIDL = 2.1e+09 
    CGIDL = 0.0002 
    PHIN =      0 
    EGIDL =    0.8 
    AIGC =  0.012 
    BIGC = 0.0028 
    CIGC =  0.002 
    AIGSD =  0.012 
    BIGSD = 0.0028 
    CIGSD =  0.002 
    AIGBACC =  0.012 
    BIGBACC = 0.0028 
    CIGBACC =  0.002 
    AIGBINV =  0.014 
    BIGBINV =  0.004 
    CIGBINV =  0.004 
    NIGC =      1 
    NIGBINV =      3 
    NIGBACC =      1 
    NTOX =      1 
    EIGBINV =    1.1 
    PIGCD =      1 
    POXEDGE =      1 
    XRCRG1 =     12 
    TNOIA =    1.5 
    TNOIB =    3.5 
    NTNOI =      1 
    XRCRG2 =      5 
    BETA0 =     30 
    IJTHDFWD =   0.01 
    IJTHSFWD =   0.01 
    IJTHDREV =  0.001 
    IJTHSREV =  0.001 
    XJBVD =      1 
    XJBVS =      1 
    BVD =     10 
    BVS =     10 
    VFB =  -0.55 
    GBMIN =  1e-10 
    RBDB =     15 
    RBPB =      5 
    RBSB =     15 
    RBPS =     15 
    RBPD =     15 
    CGSL = 2.653e-10 
    CGDL = 2.653e-10 
    CKAPPAS =   0.03 
    CKAPPAD =   0.03 
    CF = 1.16e-10 
    CLC =  1e-07 
    CLE =    0.6 
    DWC =  5e-09 
    DLC = 7.5e-09 
    DLCIG = 7.5e-09 
    DWJ =      0 
    VFBCV =     -1 
    ACDE =      1 
    MOIN =     15 
    NOFF =    0.9 
    VOFFCV =   0.02 
    DMCG =      0 
    DMCI =      0 
    DMDG =      0 
    DMCGT =      0 
    XGW =      0 
    XGL =      0 
    RSHG =    0.4 
    NGCON =      1 
    TCJ =  0.001 
    TPB =  0.005 
    TCJSW =  0.001 
    TPBSW =  0.005 
    TCJSWG =  0.001 
    TPBSWG =  0.005 
    SK0 =      0 
    SK1 =      0 
    SK2 =      0 
    SL =  2e-06 
    SW =  2e-06 
    K =      0 
    TNOM =  300.1 
    CGSO = 1.9e-10 
    CGDO = 1.9e-10 
    CGBO = 2.56e-11 
    XPART =      0 
    RSH =      5 
    JSS = 0.0001 
    JSWS =  1e-11 
    JSWGS =  1e-10 
    PBS =      1 
    MJS =    0.5 
    PBSWS =      1 
    MJSWS =   0.33 
    CJS = 0.0005 
    CJSWS =  5e-10 
    NJS =      1 
    PBSWGS =      1 
    MJSWGS =   0.33 
    CJSWGS =  3e-10 
    XTIS =      3 
    JSD = 0.0001 
    JSWD =  1e-11 
    JSWGD =  1e-10 
    PBD =      1 
    MJD =    0.5 
    PBSWD =      1 
    MJSWD =   0.33 
    CJD = 0.0005 
    CJSWD =  5e-10 
    NJD =      1 
    PBSWGD =      1 
    MJSWGD =   0.33 
    CJSWGD =  5e-10 
    XTID =      3 
    LMLT =      1 
    WMLT =      1 
    LINT = 7.5e-09 
    LL =      0 
    LLC =      0 
    LLN =      1 
    LW =      0 
    LWC =      0 
    LWN =      1 
    LWL =      0 
    LWLC =      0 
    LMIN =  1e-07 
    LMAX =  2e-05 
    WINT =  5e-09 
    WL =      0 
    WLC =      0 
    WLN =      1 
    WW =      0 
    WWC =      0 
    WWN =      1 
    WWL =      0 
    WWLC =      0 
    WMIN = 1.2e-07 
    WMAX = 0.0009 
    NOIA = 6.25e+41 
    NOIB = 3.125e+26 
    NOIC = 8.75e+09 
    EM = 4.1e+07 
    EF =      1 
    AF =      1 
    KF =      0 
    TRS =      0 
    TRD =      0

Which of these parameters is transconductance value?

Thank you.

gm is a small signal parameter of a transistor which is bias dependent. Since, it is not a model parameter, you will not find it in the transistor model.
 

Those are modle parameters and Gm is computed somehow using with these.
Refer to BSIM model book.
 

Hello, thanks for your response. Alright, as you say gm is small signal parameter which is bias dependant, so can you help me on how to do the calculation of W/L ratio for differential amplifier? May I know what BSIM model book?
 
Last edited by a moderator:

Alright, as you say gm is small signal parameter which is bias dependant, so can you help me on how to do the calculation of W/L ratio for differential amplifier?

The differential amplifier design methodology is not on top of my mind by here is how I would tackle it,

1. I have a certain gain and power requirements for the amplifier. From the DC power consumption, I could compute the DC bias current
2. Knowing the gain and a given load (RL) for the amplifier to drive, I can compute the gm of the transistor by knowing the overdrive voltage (Vd,sat=Vgs-Vth)
3. Once I have both the current and the gm, I can solve for the W/L
 

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