# Can i test my base bias circuit in this way?

Discussion in 'Homework Help' started by simpsonss, Oct 7, 2010.

1. ### simpsonss Thread Starter Active Member

Jul 8, 2008
173
0
hi,

I'm learning on base biasing for BJT. Below is the circuit. Can i test my biasing in this way?which i input a signal and have a look on the output to conclude whether it is properly bias or not. I do it in this way because i'm not sure what value should i go for the resistors. And i get this result from the Vo. And it seems like it works fine. So can i do it in this way?

thank you.

2. ### Georacer Moderator

Nov 25, 2009
5,154
1,281
If you got this output by feeding the maximum expected signal amplitude you are good to go. If signal of larger amplitude may be used on the input, try it and observe the output again.

But if you are interested in some theory on how to bias that layout in general, other members could help you better than me.

3. ### Jony130 AAC Fanatic!

Feb 17, 2009
4,868
1,364
If you want max output swing the you should always aim to set Vce = 0.5*Vcc.
So for RL =1K CE amplifier is not the bast chose.
Rc = 0.1*RL = 100Ω
Ic = 6V/100 = 60mA
Rb = β*(Vcc - Vbe) / Ic ≈ 134 * (12V - 0.79V)/ 60mA = 25KΩ
The voltage gain
Au ≈ gm* Rc||RL = 40* Ic * Rc||RL ≈ 219
And this type of bias circuit does not work good in practice.
In practice we use voltage divider and RE resistor.