Two-Stage BJT Amplifier Homework: Solving for Input Resistance and Voltage Gain

In summary, the conversation was focused on solving a circuit problem involving various equations and values for components such as beta, Rinput, Vinput, iB, IE, gm, Avo, Av, Gv, and re. The person tried to solve the problem by breaking it down into separate stages and using techniques such as DC analysis and voltage division. However, they encountered a mistake in their first handwritten equation which prevented them from completing the solution. They were advised to repeat their analysis from scratch to identify the mistake.
  • #1
Alkozy
3
0

Homework Statement


see pic in the attachment
beta = 100

Homework Equations


Rinput=Rth
Vinput=VTH
iB= ic/beta
IE=ic /alpha
iB=iE/(beta+1)
gm=IC/VT
Avo=-gmRC
Av=-gm(RC||RL)
Gv=-Beta[(RC||RL)/Rsig+(beta+1)re
re=alpha/gm

The Attempt at a Solution


solving each stage separately. First DC analysis. open all Capacitors.
V thevinin can be obtained by voltage divider = 2.88 v
R input = 31.97 K ohm
loop between the base and emitter
2.88-iB (31.97k)-0.7-iB(beta+1)(3.9k)=0
I have attached a pic of my attempt to solve it. please see attachment 2

i couldn't complete the solution
 

Attachments

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  • #2
There is an important "+" sign missing from your first handwritten equation, iB = 2.88 (31.97k ...

This is something you would have readily discovered by repeating your analysis from scratch. Often that is the most expedient course, when trying to identify ones mistake.
 

1. What is a two stage amplifier?

A two stage amplifier is an electronic circuit made up of two stages or sections, each containing a single transistor. It is used to amplify a small input signal to a larger output signal.

2. What is the difference between a one stage and two stage amplifier?

The main difference between a one stage and two stage amplifier is the number of transistor stages. A one stage amplifier has a single transistor, while a two stage amplifier has two transistors. This means that a two stage amplifier can provide a higher gain and better performance compared to a one stage amplifier.

3. How does a two stage amplifier work?

A two stage amplifier works by using two transistors to amplify a small input signal. The first stage acts as a voltage amplifier, increasing the voltage of the input signal. The second stage acts as a current amplifier, increasing the current of the signal. This results in a larger output signal with a higher gain.

4. What are the advantages of using a two stage amplifier?

There are several advantages of using a two stage amplifier, including higher gain, better stability, and lower distortion. The two stage design also allows for more precise control over the amplification process, making it suitable for a wide range of applications.

5. How do I design a two stage amplifier?

Designing a two stage amplifier involves selecting the appropriate transistors, determining the proper biasing, and calculating the resistor values for each stage. It is important to consider factors such as gain, stability, and power consumption when designing a two stage amplifier. Various online resources and textbooks can provide guidance and equations for the design process.

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