Issue in plotting equation (Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 3-by-1.)

phit=0.026;
Nd1=1e19;


ni=1.5e10;

ni=1.5e10;
q=1.6e-19;



eox=25*8.8*1e-14

eox = 2.2000e-12

tf1=5*10^-7

tf1 = 5.0000e-07

tf2=6*10^-7

tf2 = 6.0000e-07

tf3=7*10^-7

tf3 = 7.0000e-07

tf4=8*10^-7

tf4 = 8.0000e-07

tox=0.8*10^-7

tox = 8.0000e-08

Cox=eox/tox

Cox = 2.7500e-05

p1=q*Nd1*Tsc1

Unrecognized function or variable 'Tsc1'.

esi=8.8*11.7*1e-14


Qss1=3*10^-6
Qc1=2*10^-5
Ec1=1.4*10^6;


Tsc1=1*10^-6;

p1=q*Nd1*Tsc1



alpha_1=-((3*sqrt(3))/4)*(Ec1/Qss1)
beeta_1=((3*sqrt(3))/8)*(Ec1/(Qss1^3))


alpha1=2*tf1*alpha_1
beeta1=4*tf1*beeta_1


Vfb1=1.1
Vds1=0


N=30
Vgd1=linspace(0,1,N);

Qd1=zeros(1,N);



for i=1:N
    syms x
    assume(x,'real')
    eqnLeft = (Vgd1(i)-Vfb1-Vds1)+((x+p1)/Cox)+(((x+p1).^2)/(8*esi*q*Nd1))
    eqnRight =((alpha1)*((x+p1)/2))+(beeta1*((((x+p1)/2).^3)));
    Qd1(1,i)=vpasolve(eqnLeft == eqnRight,x);
    
end

plot(Vgd1,Qd1)

Answer 1

[Walter Roberson]

Your equation is a cubic. vpasolve() is going to return all three values.

phit=0.026;
Nd1=1e19;


ni=1.5e10;

ni=1.5e10;
q=1.6e-19;



eox=25*8.8*1e-14;

tf1=5*10^-7;
tf2=6*10^-7;
tf3=7*10^-7;
tf4=8*10^-7;

tox=0.8*10^-7;
Cox=eox/tox;

Tsc1=1*10^-6;

p1=q*Nd1*Tsc1;



esi=8.8*11.7*1e-14;


Qss1=3*10^-6;
Qc1=2*10^-5;
Ec1=1.4*10^6;




p1=q*Nd1*Tsc1;  %why are you re-initializing p1 ?


alpha_1=-((3*sqrt(3))/4)*(Ec1/Qss1);
beeta_1=((3*sqrt(3))/8)*(Ec1/(Qss1^3));


alpha1=2*tf1*alpha_1;
beeta1=4*tf1*beeta_1;


Vfb1=1.1;
Vds1=0;


N=30;
Vgd1=linspace(0,1,N);

Qd1 = cell(1,N);



for i=1:N
    syms x
    assume(x,'real')
    eqnLeft = (Vgd1(i)-Vfb1-Vds1)+((x+p1)/Cox)+(((x+p1).^2)/(8*esi*q*Nd1));
    eqnRight =((alpha1)*((x+p1)/2))+(beeta1*((((x+p1)/2).^3)));
    Qd1{1,i}=vpasolve(eqnLeft == eqnRight,x);
    
end

Qd1 = cell2mat(cellfun(@double,Qd1,'uniform',0))

Qd1 = 3×30

1.0e-04 * -0.0645 -0.0642 -0.0638 -0.0634 -0.0631 -0.0627 -0.0623 -0.0619 -0.0616 -0.0612 -0.0608 -0.0603 -0.0599 -0.0595 -0.0591 -0.0586 -0.0582 -0.0577 -0.0572 -0.0567 -0.0562 -0.0557 -0.0552 -0.0546 -0.0541 -0.0535 -0.0529 -0.0523 -0.0516 -0.0510 0.0074 0.0067 0.0061 0.0055 0.0049 0.0042 0.0036 0.0030 0.0023 0.0017 0.0010 0.0003 -0.0003 -0.0010 -0.0017 -0.0024 -0.0031 -0.0038 -0.0045 -0.0052 -0.0059 -0.0067 -0.0074 -0.0082 -0.0090 -0.0098 -0.0106 -0.0115 -0.0123 -0.0132 0.0993 0.0995 0.0998 0.1001 0.1003 0.1006 0.1009 0.1011 0.1014 0.1016 0.1019 0.1021 0.1024 0.1026 0.1029 0.1031 0.1033 0.1036 0.1038 0.1040 0.1043 0.1045 0.1047 0.1050 0.1052 0.1054 0.1056 0.1059 0.1061 0.1063

plot(Vgd1,Qd1)

[mohd ayaz]

I want this red line only what should i do for that? since i have to plot current using those values, and that reinitialisation is redundant i'll remove that

[Walter Roberson]

What properties of the red line allow you to distinguish it from the other lines for your purposes?

For example is the rule that you want the "middle" value at each point? If you were to extend further past 1 it looks as if somewhere near 2 the bottom (blue) line might be greater than the red line; would you want to switch to following what was then the middle value? Is the rule that you want the entry with the lowest absolute value?

[mohd ayaz]

Middle 1 has basically lowest absolute value that way we can extract,So what is the syntax for that?

[Walter Roberson]

phit=0.026;
Nd1=1e19;


ni=1.5e10;

ni=1.5e10;
q=1.6e-19;



eox=25*8.8*1e-14;

tf1=5*10^-7;
tf2=6*10^-7;
tf3=7*10^-7;
tf4=8*10^-7;

tox=0.8*10^-7;
Cox=eox/tox;

Tsc1=1*10^-6;

p1=q*Nd1*Tsc1;



esi=8.8*11.7*1e-14;


Qss1=3*10^-6;
Qc1=2*10^-5;
Ec1=1.4*10^6;




p1=q*Nd1*Tsc1;  %why are you re-initializing p1 ?


alpha_1=-((3*sqrt(3))/4)*(Ec1/Qss1);
beeta_1=((3*sqrt(3))/8)*(Ec1/(Qss1^3));


alpha1=2*tf1*alpha_1;
beeta1=4*tf1*beeta_1;


Vfb1=1.1;
Vds1=0;


N=30;
Vgd1=linspace(0,1,N);

Qd1 = zeros(1,N);



for i=1:N
    syms x
    assume(x,'real')
    eqnLeft = (Vgd1(i)-Vfb1-Vds1)+((x+p1)/Cox)+(((x+p1).^2)/(8*esi*q*Nd1));
    eqnRight =((alpha1)*((x+p1)/2))+(beeta1*((((x+p1)/2).^3)));
    temp = sort(double(vpasolve(eqnLeft == eqnRight,x)));
    Qd1(i) = temp(2);
end

plot(Vgd1,Qd1)

[mohd ayaz]

Thanks