12
BJT Small-Signal Models
•h-parameter
model
–More
complex
–Better
for ac operation
–Common
Emitter model
•hie = input impedance (Ω)
•hre = reverse voltage transfer ratio (unitless)
•hfe = forward current transfer ratio (unitless)
•hoe =
output admittance (S)
hfeib
B
E
hie
iC
ie
ib
hreVce
1/hoe