TransWikia.com

How to calculate small signal parameter for a BJT when early voltage is taken into consideration?

Electrical Engineering Asked by SUNITA GUPTA on January 29, 2021

I have proved one formula of

output impedance
ro = (Va+Vce)/Ic = Va/Ic’

where Ic is collector current and Ic’ is collector current neglecting early effect.

But reading from standard texts other formulas are diverging like for
gm{trans-conductance} = Ic/Vt

is formula given in Razavi, Neamen .

But I am getting

gm=β/rb = Ic’/Vt

where rb is base emitter resistance and β is common emitter current gain.

Am I doing some mistake or its rather approximation the books are taking and in later case plz comment if the approximation is rather universally valid.

One Answer

Model those like this

schematic

simulate this circuit – Schematic created using CircuitLab

Answered by analogsystemsrf on January 29, 2021

Add your own answers!

Ask a Question

Get help from others!

© 2024 TransWikia.com. All rights reserved. Sites we Love: PCI Database, UKBizDB, Menu Kuliner, Sharing RPP