Cork Institute of Technology
Bachelor of Engineering in Applied Electronics Design - Award
(NFQ Level 7)
Semester 1 2005/2006
Audio-Visual Electronics
(Time: 1.5 Hours)
Answer THREE questions.
All questions marked out of 100 marks
Examiners: Dr B.V.Donovan
Mr. J. Berry
Dr. R. O Dubhghaill
Q1. Both T. A. Edison and Emile Berliner were pioneers in the in the area of ‘recording and
play-back’ of sound at the end of the 19th Century.
a) Describe the technology/ principles of operation, of their recording/play-back devices.
[2 x 20 Marks]
b) How did they differ in their ‘markets’?
[2 x 15 Marks]
c) Describe why the Berliner design/device was the more successful ultimately.
[30 Marks]
Q2 Write a brief note on ‘noise’ in electronic circuits.
[20 Marks]
What is the difference between ‘white noise’ and interference?
[2 x 20 Marks]
What is the source of Johnson Noise, so common in electronic amplifiers?
[15 Marks]
A pre-amplifier which has an input impedence of 50kΏ and a bandwidth of 15kHz is fed a
signal of 100mV r.m.s.. Assuming a perfect amplifier, calculate the Signal to Noise Ratio at the
output in dB.
[25 Marks]
{ Vnoise (r.m.s.) = 0.13 √ [R(∆f)] µV . R is in MΏ, ∆f in Hz }
