%BJT Common Base/Emitter Input/Output Characteristics

%Modified version of BJT including Base-Width Modulation and

  %Carrier Multiplication



%Input Eber-Moll Parameters

bjt0



%Limiting Voltages used in Calculation

VbiE=kT*log(NE*NB/ni^2);

VbiC=kT*log(NC*NB/ni^2);

VCB0= 60*(NC/1.0e16)^(-3/4);

m=6;  VCE0=VCB0*(1-aF)^(1/m);



%Choice of Characteristic and Special Calculations

format compact

echo on

%THIS PROGRAM COMPUTES BJT INPUT AND OUTPUT CHARACTERISTICS

% Subprograms BJT0 and BJTmod are run-time requirements.

% Modify entries in BJT0 to change device/material parameters.

% Modify axis commands to change plot min/max values.

echo off

close

c=menu('Specify the desired characteristic','Common Base Input',...
   'Common Base Output','Common Emitter Input','Common Emitter Output');

j=input('Specify number of curves per plot...');

if c~=2,

     bw=input('Include base-width modulation?  1-Yes, 2-No...');

     else

     end

ii=2;

if c==4 & bw==1,

     ii=input('Include impact ionization?  1-Yes, 2-No...');

     else

     end



%Calculation Proper

for i=1:j,



     %Common-Base Input Characteristics

     if c==1,

     VCB=-(i-1)*10;

     VEB=0:0.005:VbiE;

     jj=length(VEB);

         if bw==1,

         bjtmod     %Base-Width Modulation subprogram

         else

         end

     IE=(IF0.*(exp(VEB/kT)-1) - aR.*IR0.*(exp(VCB/kT)-1))*1.0e3;

     %1.0e3 in the preceeding equation changes IE units to mA

     if i==1,

     plot(VEB,IE);  axis([0.35 0.85 0 5]);

     grid;  xlabel('VEB(volts)');  ylabel('IE(mA)');

     else plot(VEB,IE);

     end



     %Common-Base Output Characteristics

     elseif c==2,

     IE=(j-i)*1.0e-3;    

     VCB1=2:-0.01:0;

     VCB2=0:-VCB0/200:-VCB0;

     VCB=[VCB1,VCB2];

     jj=length(VCB);

     IC=(aF*IE-(1-aF*aR)*IR0*(exp(VCB/kT)-1))*(1.0e3);

     if i==1,

     plot(-VCB,IC);  axis([-VCB0/10 VCB0 0 1.3e3*IE]);

     grid;  xlabel('-VCB(volts)');  ylabel('IC(mA)');

     text(5,1.1e3*IE,'IEstep=1mA');

     else plot(-VCB,IC);

     end



     else

     end



     %Common-Emitter Input Characteristics

     if c==3,

     VEC=(i-1)*5;

     VEB=0:0.005:VbiE;

     jj=length(VEB);

         if bw==1,

         VCB=VEB-VEC;

         bjtmod

         else

         end

     IB0=(1-aF).*IF0+(1-aR).*IR0;

     IB1=(1-aF).*IF0+(1-aR).*IR0.*exp(-VEC/kT);

     IB=(IB1.*exp(VEB/kT)-IB0)*(1.0e6);

     if i==1,

     plot(VEB,IB);  axis([.35 .85 -5 20]);

     grid;  xlabel('VEB(volts)');   ylabel('IB(uA)');

     else plot(VEB,IB);

     end



     %Common-Emitter Output Characteristics

     elseif c==4,

     IB=(j-i)*2.5e-6;

     VECA=0:0.01:VCE0/50;

     VECB=VCE0/50:VCE0/200:VCE0;

     VEC=[VECA,VECB];

     jj=length(VEC);

         if bw==1,

         VEB=0;  %Neglect xnEB variation with bias

         VCB=VEB-VEC;

         bjtmod

         else

         end

         if ii==1,

         M=1.0./(1-(-VCB/VCB0).^m);

         aF=M.*aF;

         else

         end

     IB0=(1-aF).*IF0+(1-aR).*IR0;

     IB1=(1-aF).*IF0+(1-aR).*IR0.*exp(-VEC/kT);

     IC=((aF.*IF0-IR0.*exp(-VEC/kT)).*(IB+IB0)./IB1+IR0-aF.*IR0)*(1.0e3);

     if i==1,

     jA=length(VECA);

     plot(VEC,IC);  axis([0 VCE0 0 2.5*IC(jA)]);

     grid;  xlabel('VEC(volts)');  ylabel('IC(mA)');

     text(5,2*IC(jA),'IBstep=2.5uA');

     else plot(VEC,IC);

     end



     else

     end



hold on

end

hold off