Having an issue with a small homework assignment. The question asks what the overall voltage gain is for the three stage amplifier in the attached picture below.
We were told to assume Hfe = 200
Here's the calculations and formulas I have thus far:
Zin Base (1) = Rswamp(R4) x Hfe = 1k ohms x 200 = 200k ohms
Zin Base (2) = Rswamp(R8) x Hfe = 100 ohms x 200 = 20k ohms
Zin Base (3) = Rload x Hfe = 100 ohms x 200 = 20k ohms
Av (1) = R1//R2//Zin Base (1) = 10k//5.6k//200k = 3.53k ohms
Av (2) = R5//R6//Zin Base (2) = 12k//1k//20k = 882 ohms
Av (3) = Have not figured that out, kind of assuming R7//R8//Zin Base (3)
Now the back of the book gives me a gain of 1679, but various other calculations I've messed around with do not give me that answer.
Can anyone help clear this up for me?
We were told to assume Hfe = 200
Here's the calculations and formulas I have thus far:
Zin Base (1) = Rswamp(R4) x Hfe = 1k ohms x 200 = 200k ohms
Zin Base (2) = Rswamp(R8) x Hfe = 100 ohms x 200 = 20k ohms
Zin Base (3) = Rload x Hfe = 100 ohms x 200 = 20k ohms
Av (1) = R1//R2//Zin Base (1) = 10k//5.6k//200k = 3.53k ohms
Av (2) = R5//R6//Zin Base (2) = 12k//1k//20k = 882 ohms
Av (3) = Have not figured that out, kind of assuming R7//R8//Zin Base (3)
Now the back of the book gives me a gain of 1679, but various other calculations I've messed around with do not give me that answer.
Can anyone help clear this up for me?
Attachments

288.8 KB Views: 84
Last edited: