### Author Topic: The Common Emitter Amplifier Circuit  (Read 82435 times)

#### Fu-Kwun Hwang

• Hero Member
• Posts: 3062
##### The Common Emitter Amplifier Circuit
« on: February 26, 2011, 02:41:00 pm »
The following is a simulation for a Common Emitter Amplifier Circuit.

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The single stage common emitter amplifier circuit shown above uses what is commonly called "Voltage Divider Biasing". This type of biasing arrangement uses two resistors as a potential divider network and is commonly used in the design of bipolar transistor amplifier circuits. This method of biasing the transistor greatly Voltage Divider Network reduces the effects of varying Beta, ( ? ) by holding the Base bias at a constant steady voltage level allowing for best stability. The quiescent Base voltage (Vb) is determined by the potential divider network formed by the two resistors, R1, R2 and the power supply voltage Vcc as shown with the current flowing through both resistors. Then the total resistance RT will be equal to R1 + R2 giving the current as i = Vcc/RT. The voltage level generated at the junction of resistors R1 and R2 holds the Base voltage (Vb) constant at a value below the supply voltage. Then the potential divider network used in the common emitter amplifier circuit divides the input signal in proportion to the resistance.
\$V_B=frac{R2}{R1+R2}Vcc\$

Then \$V_{RE}=V_B-V_{BE}\$ (assume \$V_{BE}=0.7V\$)
\$I_E=frac{V_{BE}}{R_E}\$
and
\$I_E=I_C+I_B=(1+eta) I_B\$
So \$I_C=eta I_B=frac{eta}{1+eta}I_E\$
Finally, \$V_{CE}=V_{cc}-V_{RL}-V_{RE}=\$ \$V_{cc}-I_C R_L-I_E R_E>V_{sat}\$
(\$V_{sat}=0.2V\$)

You are welcomed to check out similar applet at Common Emitter Transistor Amplifier

#### moraein

• Newbie
• Posts: 1
##### Re: The Common Emitter Amplifier Circuit
« Reply #1 on: June 24, 2013, 08:45:33 pm »
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=2116.0

Hi i enjoyed with your simulation. very nice

I need Vcc=12 and Rl=10k .. can u do it for me ?

#### Fu-Kwun Hwang

• Hero Member
• Posts: 3062
##### Re: The Common Emitter Amplifier Circuit
« Reply #2 on: June 25, 2013, 12:10:58 am »
You can adjust parameters with sliders from the simulated circuit. Try it!
You need to adjust R1 and R2.

#### jn300

• Newbie
• Posts: 1
##### Re: The Common Emitter Amplifier Circuit
« Reply #3 on: December 28, 2013, 03:04:38 am »
Hi, I stumbled across this very useful simulation and it has helped me somewhat. I know this is slightly off topic to what you posted, but I was wondering how exactly do you determine individual component values for a common emitter circuit with only 2 variables given. vcc=12v and voltage gain being 10.

thank you