Help with bjt amplifier design

  • #1

Homework Statement


given input as 100mV peak and expected output to be 10Vpeakto peak....i am having trouble on how to find the different values , like resistors , capacitors ...i am planning to use fixed bias circuit (common emitter configuration) and my transistor gives a value of hfe= min(40) max(150) ,Vce=10V and Ic=150mA...


Homework Equations


Ib=(Vcc-Vbe)/(Rb)
Ic=beta(Ib)
Vce= Vcc-IcRc
Vce=Vc-Ve


The Attempt at a Solution


i solve for the value of hfe using geometric mean square root of (40*150) = 69
and voltage gain to be 50
 

Answers and Replies

  • #2
1,762
59
Do you know the input and output impedances to your amplifier?

Using the geometric mean for hfe is not a good idea. Transistors significantly below that value won't have enough gain and one significantly above that value may clip the output. The usual solution is to reduce the range of the transistor gains with negative feedback.

Do you know how to introduce negative feedback in an amplifier? Can you suggest a method for doing that?
 

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