Hi,
I want to change the model of Schottky diode which is avilable in Cadence ahdlLib.
I want to know the $Vt and what $ indicates in veriloga code?

 Vd = V(vanode, vcathode);
`ifdef __VAMS_ENABLE__
     Id = I(<vanode>);
`else
     Id = I(vanode, vanode);
`endif
     // intrinsic diode.
     if (Vd < -5*n*$vt) begin
        if (Vd == -bv) begin
           I(vanode, vcathode) <+ -area*ibv;
        end else if (Vd > -bv) begin
           I(vanode, vcathode) <+ -area*is;
        end else begin
           I(vanode, vcathode) <+ -area*is*(exp(-(bv + Vd)/$vt) -
              1 + bv/$vt);
        end
     end else begin
        I(vanode, vcathode) <+ area*is*(exp((Vd - rs*Id)/(n*$vt)) - 1);
     end      

     I(vanode, vcathode) <+ gmin * Vd;
     // capacitance (junction and diffusion).
     if (Vd <= fcp) begin
        Qd = tt*Id  + area*cjo*phi*(1 - pow((1 - Vd/phi), (1 - m)))/(1 - m);
     end else begin
        Qd = tt*Id + area*cjo*(f1 + (1/f2)*(f3*(Vd - fcp) + (0.5*m/phi)*
           (Vd*Vd - fcp*fcp)));
     end
     I(vanode, vcathode) <+ ddt(Qd);

The $ (dollar sign) is usually used for "system functions and tasks," ie, things the simulator handles:  $strobe, $fopen, etc.  Also $temperature, which is the simulation temperature.

gmadhavareddy wrote on Sep 28^th, 2006, 8:11am:

1) As ken said, $vt is kT/q, the thermal voltage. so NO $vt does not reperesent threshold voltage
2) .