I am having some problems finding certain values on the following circuit:
http://img268.imageshack.us/img268/5766/questionyyw.jpg
I started the circuit by finding the base voltage of both stages by using the equation: VB 1 or VB1= VCC x R2 / (R1 + R2)
I then found Ve for both stages by subtracting .7 from VB
I found IE of both stages by= (VB -.7)/ (RE + other resistor between emitter and ground)
I found the AC emitter resistance of both stages by using the following equation: 25 mv/IE
After this point I had some difficulties. I realized the the equations I was able to use with a single stage common emitter BJT were not working such as:
ZIN BASE = hfe x r’e --- which I used for single stage was no longer working, but I don't think the value of hfe is given. What would Q1/hfe mean?
ZIN = R1 II R2 II ZIN (Base) -- I used this for single stage as well and no longer seems to work for two stage.
There are several voltage gain values needed, can anyone explain the difference between them, what they are for, and how to calulate them. For single stage I would use the equation: AV= rC/ r’e
Also how is the voltage across Rload found?
So as a summary I am unable to find the following values:
Zin (base)
rc1
Zin
Av (all of them)
VRload
I would really appreciate any help. You guys have been been great so far.
http://img268.imageshack.us/img268/5766/questionyyw.jpg
I started the circuit by finding the base voltage of both stages by using the equation: VB 1 or VB1= VCC x R2 / (R1 + R2)
I then found Ve for both stages by subtracting .7 from VB
I found IE of both stages by= (VB -.7)/ (RE + other resistor between emitter and ground)
I found the AC emitter resistance of both stages by using the following equation: 25 mv/IE
After this point I had some difficulties. I realized the the equations I was able to use with a single stage common emitter BJT were not working such as:
ZIN BASE = hfe x r’e --- which I used for single stage was no longer working, but I don't think the value of hfe is given. What would Q1/hfe mean?
ZIN = R1 II R2 II ZIN (Base) -- I used this for single stage as well and no longer seems to work for two stage.
There are several voltage gain values needed, can anyone explain the difference between them, what they are for, and how to calulate them. For single stage I would use the equation: AV= rC/ r’e
Also how is the voltage across Rload found?
So as a summary I am unable to find the following values:
Zin (base)
rc1
Zin
Av (all of them)
VRload
I would really appreciate any help. You guys have been been great so far.