The following circuit is an AM radio. If you look closely at it you will note th
ID: 2081569 • Letter: T
Question
The following circuit is an AM radio. If you look closely at it you will note that is just an L-C circuit in series with three common emitter amplifiers. Complete the design by choosing R_1, R_2, R_3, R_4, R_5, and R_6. The resistors R_1, R_3, and R_5 are the bias resistors. Choose them such that at the operating point 1 to 10 mu A flows into the base of each transistor. The other three resistors (R_2, R_4, R_6) determine the gain of each amplifier stage. Choose these resistors to give each stage (transistor) a gain of about 50. Assume the beta of each transistor is 100. What is the gain of each stage (transistor)? Which stage performs amplitude demodulation (what is amplitude demodulation)?Explanation / Answer
1) Ans: Amplitude Modulation:It is defined as the Process of changing the Amplitude of Carrier in accordence with the instantaneous Amplitude of modulating signal.
Given data:
Gain of First Stage: Av1=50
Gain of Second Stage:Av2=50
Gain of Third Stage :Av3=50
biasing Resistors:
R1=?
R3=?
R5=?
Amplification Factor Beta =100
Gain of Individual Amplifiers =50
Base Current Ib=0 -10micro Amps
so
IB=Ib1+Ib2+Ib3=0 -10micro Amps
Ib1=3micro Amps R1=V/Ib1 =3V/3micro=1M ohm
ib2=3micro Amps R3=V/Ib2 =3V/3micro=1M ohm
ib3=4mico Amps R5=V/Ib3 =3V/4mico =0.75M ohm or 750K ohm
Generally we know the gain of Common Emitter amplifier Gain Formula is=( -Rc||RL)/re
Where re=Ri/Beta value
Av1=50=[R2||1M ohm || (100re)]/re
R2=we will get it by solving
Av2=50=[R4||1M ohm || (100re)]/re
R4=we will get it by solving
Av3=50=[R6||1M ohm || (100re)]/re
R6=we will get it by solving
2)Ans:Amplitude Demodulation:It is the process of separating or decoding the message or modulating signal from the modulated carrier signal.
Gain of First Stage: Av1=50
Gain of Second Stage:Av2=50
Gain of Third Stage :Av3=50
Overall Gain Av=Av1*Av2*Av3=50*50*50=125000
in Db=20Log10(50)3
=20*3Log10(50)
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.