You may wish to run the following design case, to see if there might be any errors in your equations.
BJT Design
Parameters:
WE
= 0.2 mm;
NDE
=
1019 cm-3
WB
= 0.2 mm;
NAB
=
1017 cm-3
WC
= 2.0 mm;
NDC
=
1016 cm-3
At T = 300K:
niE = 4.3x1010 cm-3
Minority-carrier mobilities: mE = 69 cm2/Vs; mB = 774 cm2/Vs; mC = 437 cm2/Vs
Minority-carrier diffusion lengths: LE = 13.3 mm; LB = 44.7 mm; LC = 33.6 mmZero-bias pn-junction depletion widths: WdepBE = 0.12 mm; WdepBC = 0.33 mm
VBE = 0.806V to achieve IC = 1 mA
Performance Parameters at IC = 1 mA:
tF = 4.7 psbdc = ~110 VA = ~5.5 V VPT = ~4.0 V fT = ~20.4 GHz