How to compute low noise voltage.

[John Schypes]

Hello Guys, am John and i have an assignment that i am requesting for your guidance and advice. Its a take away assignment from our proffessor and its a tough one. He has allowed us to take our own values for the question.
Three dry cells each having internal resistance of R1� and an e.m.f of V1 are in series with a R2� receiver and a R3� transmitter to form a simple telephone circuit. The connecting wires have a total resistance of R4� and low noise amplifier of R5�. Compute the low noise amplifier voltage.

 

[Harald Kapp]

Welcome to EP, John.

As I see it, this question is not about noise voltage but about the input voltage to the (low noise) amplifier.
Start by drawing the circuit diagram (schematic) which shows the dry cells, receiver, transmitter, wires and amplifier and how these are connected.
From the schematic you can derive the necessary equations by applying Kirchhoff's laws.

Show us your diagram for further discussion.

 

[dorke]

Welcome to EP .

Did your professor teach you about resistor thermal noise?
Draw the circuit as described with all resistances and calculate the noise.