# Designing DC Bias Circuit

#### sparkey2000

Joined Mar 9, 2008
8
Please can someone help me answer the attached question; I can work through examples and calculate IC, IE, VCE, IB and VBE etc.

However I'm stuck with the following question and I will need to do this for an exam this week; and help will be much appreciated.

#### Attachments

• 38.8 KB Views: 44

#### beenthere

Joined Apr 20, 2004
15,819
What results have you got for the problem?

#### yubyub

Joined Aug 13, 2008
19
Rc + Re ~= 16k, since Vcq = Vcc/2, Rc ~= Re = 8k

Ib ~= 6.67µA R1 ~= 2.4M (i think?) R2 = R1?

Those are approximations, and i'm not sure about R1, R2. The lack of working would cause you to get no marks though.

Assuming you have a textbook with BJT's, you should have no problem doing the working out properly.

#### mik3

Joined Feb 4, 2008
4,843
Please can someone help me answer the attached question; I can work through examples and calculate IC, IE, VCE, IB and VBE etc.

However I'm stuck with the following question and I will need to do this for an exam this week; and help will be much appreciated.
Vcq equals 8 volts because it is half the Vcc, thus Rc=(Vcc-Vcq)/Ic

Rc=8V/1mA=8K

then we assume that Ie equals Ic and that Ve equals Vcc/10

thus Re=Ve/Ie=1.6V/1mA=1.6K

then we assume that R2 equals 0.1*150*Re

thus R2=24K

then Vb equals Ve+0.7=2.1V

then make the voltage divider equation to find R1
{"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0}