# set terminal pngcairo  transparent enhanced font "arial,10" fontscale 1.0 size 500, 350 
# set output 'electron.2.png'
set dummy Vd,y
set key at 0.2, 0.0045, 0 right top vertical Right noreverse enhanced autotitles box linetype -1 linewidth 1.000
unset key
set label 1 "-0.5 Vp" at 4.1, 0.625, 0 left norotate back nopoint offset character 0, 0, 0
set label 2 "-0.25 Vp" at 4.1, 1.4, 0 left norotate back nopoint offset character 0, 0, 0
set label 3 "0" at 4.1, 2.5, 0 left norotate back nopoint offset character 0, 0, 0
set label 4 "Vg = 0.5 Vp" at 4.1, 3.9, 0 left norotate back nopoint offset character 0, 0, 0
set samples 160, 160
set title "JFET Mutual Characteristic" 
set xlabel "Drain voltage Vd (V)" 
set xrange [ 0.00000 : 4.00000 ] noreverse nowriteback
set ylabel "Drain current Id (mA)" 
set yrange [ 0.00000 : 5.00000 ] noreverse nowriteback
set rmargin  12
Ie(Vbe)=Ies*exp(Vbe/kT_q)
Ic(Vbe)=alpha*Ie(Vbe)+Ico
Ida(Vd)=Ido*(1-Vg/Vp)**2
Idb(Vd)=Ido*(2*Vd*(Vg-Vp)-Vd*Vd)/(Vp*Vp)
Id(Vd)= (Vd>Vg-Vp) ? Ida(Vd) : Idb(Vd)
Ies = 4e-14
kT_q = 0.025
GPFUN_Ie = "Ie(Vbe)=Ies*exp(Vbe/kT_q)"
alpha = 0.99
Ico = 1e-09
GPFUN_Ic = "Ic(Vbe)=alpha*Ie(Vbe)+Ico"
Ido = 2.5
Vg = 0.3125
Vp = -1.25
GPFUN_Ida = "Ida(Vd)=Ido*(1-Vg/Vp)**2"
GPFUN_Idb = "Idb(Vd)=Ido*(2*Vd*(Vg-Vp)-Vd*Vd)/(Vp*Vp)"
GPFUN_Id = "Id(Vd)= (Vd>Vg-Vp) ? Ida(Vd) : Idb(Vd)"
plot Vg=0.5*Vp,Id(Vd),Vg=0.25*Vp,Id(Vd),Vg=0,Id(Vd),Vg=-0.25*Vp,Id(Vd)