Ai=Av*hfeA1=Ai*Rc/RbSolving Amplifier Questions with Low Frequencies

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In summary, the conversation discusses an amplificator of low frequencies and its h parameters. The poster has created a pi model and asks for help in finding several parameters including A1, Ais, Av, Avs, Ri, Ri', R0, and R0'. The conversation also mentions the need for defining each parameter.
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Homework Statement



We have an amplificator of low frequences like in the figure.The transistor has these h parameters:
hie=1.1k Ohm,hfe=50 Ohm
In the entrance we have Vs and Rs=10 kOhm.
Find A1,Ais,Av,Avs,Ri,Ri',R0 and R0'


Homework Equations



There are many.

The Attempt at a Solution


I ,myself did the pi model like in the figure.Is it correct?
Please,check if I have put Rb in the right place in the pi equivalent
http://i.imgur.com/ClGTLdd.jpg

ALSO,can you please help me find what is asked?
I think that
V0=i0*Rc=-gm*vpi*Rc
Vi=ib*(Rb|| rpi)=Vpi*(Rb/(Rb+rpi)
Av=V0/Vi
Avs=[Ri/(Ri+Rs)]*Av
 
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  • #2
hfe is dimensionless. Your value of 50 looks too low anyway.

Your model looks OK. Did you compute Rpi?

You are nasking for a lot of parameters and need to define each of them for us.
 

Related to Ai=Av*hfeA1=Ai*Rc/RbSolving Amplifier Questions with Low Frequencies

1. What is the purpose of using Ai=Av*hfeA1=Ai*Rc/Rb in amplifier circuits?

The equation Ai=Av*hfeA1=Ai*Rc/Rb is used to calculate the gain of an amplifier circuit. This gain is important because it determines how much the input signal is amplified by the circuit. By using this equation, scientists can design and optimize amplifier circuits for specific applications.

2. How does low frequency affect the performance of an amplifier circuit?

Low frequency signals can affect the performance of an amplifier circuit in several ways. Firstly, it can cause distortion in the output signal, resulting in a loss of fidelity. Additionally, low frequency signals can also introduce noise into the circuit, reducing the signal-to-noise ratio and impacting the overall performance.

3. What is the significance of Rc and Rb in the equation Ai=Av*hfeA1=Ai*Rc/Rb?

Rc and Rb are the collector and base resistors, respectively, in an amplifier circuit. These resistors help determine the overall gain of the circuit by controlling the flow of current through the circuit. By adjusting the values of these resistors, scientists can fine-tune the gain of the circuit to meet their specific requirements.

4. How does hfe (current gain) affect the overall gain of an amplifier circuit?

Hfe, also known as the current gain, represents the ratio of output current to input current in a transistor. This value is important in amplifier circuits because it directly affects the overall gain of the circuit. A higher hfe value means a higher gain, while a lower hfe value means a lower gain. Therefore, selecting a transistor with an appropriate hfe value is crucial in designing an amplifier circuit with the desired gain.

5. Can the equation Ai=Av*hfeA1=Ai*Rc/Rb be used for all types of amplifier circuits?

While the equation Ai=Av*hfeA1=Ai*Rc/Rb is commonly used in many amplifier circuits, it may not apply to all types of amplifiers. This equation is primarily used for common-emitter amplifiers, and different types of amplifiers, such as common-collector or common-base amplifiers, may require different equations to calculate the gain. It is important to understand the circuit design and specifications before using this equation for gain calculation.

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