1. The following table gives measured values of the noise figure F of an amplifier of gain 100 for a range of source res

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1. The following table gives measured values of the noise figure
F of an amplifier of gain 100 for a range of source resistances
RS. RS / ohm F
100
4.50
1k
1.38
10k
1.29
100k
3.50 a)
a) Using the data in the table, determine the optimum noise
figure for the amplifier and the source resistance necessary to
achieve it. Include a full explanation of all the steps in your
calculations. (9 marks)
b) The amplifier is to be used to amplify the signal from a
transducer. Suitable transducers are available with resistances
ranging between 50 – 100 Ω. Fully explaining your reasoning and all
the steps in your calculations, determine what transducer
resistance should be chosen to optimise the system detectivity and
by what factor the system detectivity is improved or degraded when
this resistance is used rather than the resistance that gives the
optimum noise figure for the amplifier. (11 marks)