cut-off

Ic, Ie, Ib = 0

Saturation

Vbe = 0.7

Vbc = 0.5

Vce = 0.2

No Constraints on Current

B-E Juncion = ON

B-C Junction = OFF

Forward Active

Vbe=0.7, Vbc < 0.5

Vbe(on) - Vbc(on) = Vce(sat)

Ie = Ies(e^(Vbe/Vt))

Ic=α_f*Ies(e^(Vbe/Vt))

Ib = (1-α_f)Ies(e^(Vbe/Vt))

Ic/Ib=α_f/(1-α_f) = β_f (usually 100)

Ic/Ie = α_f

B-E Junction = Off

B-C Junction = On

reverse active

Ic = -Ics(e^(Vbc/Vt))

Ie = -α_r*Ics(e^(Vbc/Vt))

Ib = (1-α_r)Ics(e^(Vbc/Vt))

Ie/Ib=α_r/(1-α_r) = β_r (usually about 1)

r_Π

r_{Π=Vt/Ib = (βf*Vt)/Ic}

(bjt)

gm 

gm = Ic/Vt

(bjt)

r_o

r_o = Va/Ic

(bjt)

IcRc

IcRc = Vcc - Vout(opt) = 1/2[Vcc - Vce(sat)]

(mosfet)

gm

gm = 2*Id/(Vgs-Vt)

(mosfet)

ro

ro = 1/(λ * Id)

Vin(dm)

Vin(dm) = Vin₊ - Vin_-

Vin(cm)

Vin(cm) = (1/2)* ( Vin₊ + Vin_-)

(bjt)

gm(Re) (for common collector)

gm(Re) = α_f * Ie*Re/Vt