BJT small signal analysis

[Betta]

Hi all

Who can tell me how can i go from one model to another, i mean Re to R-pi,check out the attachment!

Thanks a lot

 

[junas]

hey,
these relations should help-
1. r-pi=beta(hie)*re
2. gm=1/re
3.ro=1/hoe
4. hre=r-pi/(r-pi +ru)