BSIM3v3.2.2 MOSFET Model - The University of Texas at Dallas
BSIM3v3.2.2 MOSFET Model - The University of Texas at Dallas
BSIM3v3.2.2 MOSFET Model - The University of Texas at Dallas
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Strong Inversion Current and Output Resistance (S<strong>at</strong>ur<strong>at</strong>ion Regime)<strong>The</strong> parameters A i and B i are determined from extraction. I sub will affectthe drain current in two ways. <strong>The</strong> total drain current will change because itis the sum <strong>of</strong> the channel current from the source as well as the substr<strong>at</strong>ecurrent. <strong>The</strong> total drain current can now be expressed [21] as followsI = Idso+ Ids⎡⎢= Idso⎢1+Bi⎢⎣ Aisub⎤( Vds− Vds<strong>at</strong>)⎥Bl ⎥iexp( ) ⎥Vds− Vds<strong>at</strong>⎦(2.6.14)<strong>The</strong> total drain current, including CLM, DIBL and SCBE, can be written as(2.6.15)Vds− Vds<strong>at</strong>Vds− Vds<strong>at</strong>Ids = Wvs<strong>at</strong>Cox ( Vgst − AbulkVds<strong>at</strong>)( 1+)( 1+)V VASCBEwhere V ASCBE can also be called as the Early voltage due to the substr<strong>at</strong>ecurrent induced body effect. Its expression is the followingAVASCBE=BiBl iexp( )AiVds− Vds<strong>at</strong>(2.6.16)From Eq. (2.6.16), we can see th<strong>at</strong> V ASCBE is a strong function <strong>of</strong> V ds . Inaddition, we also observe th<strong>at</strong> V ASCBE is small only when V ds is large. Thisis why SCBE is important for devices with high drain voltage bias. <strong>The</strong>channel length and g<strong>at</strong>e oxide dependence <strong>of</strong> V ASCBE comes from V ds<strong>at</strong> andl. We replace Bi with PSCBE2 and Ai/Bi with PSCBE1/L to yield thefollowing expression for V ASCBE<strong>BSIM3v3.2.2</strong> Manual Copyright © 1999 UC Berkeley 2-29
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