# Question about transistor biasing

Thread Starter

#### hkntrt

Joined Jun 20, 2012
13
Firstly i want to say thanks for that great documentation.I have a question about transistor biasing formula used in that lesson.Why Re resistor is 470Ω ?
My calculation is wrong ?

#### t_n_k

Joined Mar 6, 2009
5,455
Actually

$$V_{BB}=I_BR_B+V_{BE}+V_E$$

Thread Starter

#### hkntrt

Joined Jun 20, 2012
13
Hmmm 1μA . 33κΩ = 0.33 V

1.5 V = 0.33 V + 0.7 V + Ve

Ve=0.47

Ic = 1 mA

Ic≈Ie

0.47 V / 1 mA = 470 Ω

Now i understood , thanks #### Rbeckett

Joined Sep 3, 2010
208
Firstly i want to say thanks for that great documentation.I have a question about transistor biasing formula used in that lesson.Why Re resistor is 470Ω ?
My calculation is wrong ?
What lesson are you talking about? Which book, and chapter are you looking at please. I missed that so I had better go and learn it now, before I get into a mess.
Thanks.
Wheelchair Bob

#### absf

Joined Dec 29, 2010
1,949
They are discussing about Vol 3 (semiconductor) Chapter 4 - biasing calculations http://www.allaboutcircuits.com/vol_3/chpt_4/10.html

Allen

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