Help with bjt amplifier design

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SUMMARY

The forum discussion focuses on designing a BJT amplifier using a common emitter configuration with a fixed bias circuit. The user is tasked with calculating component values for a circuit that takes a 100mV peak input and outputs 10V peak-to-peak. Key parameters include a transistor with a minimum hFE of 40 and a maximum of 150, with a collector current (Ic) of 150mA. The discussion highlights the importance of avoiding reliance on the geometric mean for hFE and suggests implementing negative feedback to stabilize gain and prevent clipping.

PREREQUISITES
  • Understanding of BJT amplifier configurations
  • Knowledge of fixed bias circuits
  • Familiarity with transistor parameters such as hFE and Ic
  • Basic principles of negative feedback in amplifiers
NEXT STEPS
  • Research methods for calculating resistor and capacitor values in BJT amplifiers
  • Learn about implementing negative feedback in amplifier circuits
  • Study the effects of input and output impedance on amplifier performance
  • Explore the impact of varying hFE on amplifier gain and stability
USEFUL FOR

Electronics students, circuit designers, and hobbyists interested in BJT amplifier design and optimization techniques.

herbgriffin
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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
 
Physics news on Phys.org
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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