# Vol III - BJT - Bias Calculations missing assumption?

Discussion in 'Feedback and Suggestions' started by deBooglel, Nov 26, 2012.

1. ### deBooglel Thread Starter New Member

Nov 26, 2012
1
0
Hi there,

I could be wrong but in the section for the Bias Calculations using the collector feedback method the following is stated based on KVL:

Vcc-IcRc-IbRb-Vbe = 0

I think technically the voltage across Rc is (Ic + Ib)Rc, but as Ic is much much greater than Ib we can assume Ib is negligible. BUT this assumption was not stated and therefore technically the KVL equation is wrong!

I might be wrong though!

D

2. ### Georacer Moderator

Nov 25, 2009
5,150
1,271
The assumption is stated, even if not explicitly. You can read $I_c=(\beta +1) I_b \approx \beta I_c$

I guess it could be more clear, but then again, space and coherence is an issue.

3. ### tshuck Well-Known Member

Oct 18, 2012
3,527
679
Look at line 1: $I_{C}\approx I_{E}$