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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Summer Examinations 2010
Module Title: Analogue Electronics 2
Module Code: ELTR
School: Electrical & Electronic Engineering
Programme Titles: Bachelor of Engineering in Electronic Engineering Bachelor of Engineering (Honours) in Electronic Systems Engineering
Programme Codes: EELXE_7_Y EELES_8_Y
External Examiner(s): Dr. A. Donnellan Dr. P. O’Sullivan Internal Examiner: Mr. M. O’Gorman
Instructions: Answer Question 1 and TWO other questions. Question 1 (worth 40 marks) is compulsory. Questions 2, 3, and 4 are each worth 30 marks.
Duration: 2 Hours
Sitting: Summer 2010
Requirements for this examination: N/A
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you are attempting the correct examination paper. If in doubt please contact an Invigilator.
COMPULSORY QUESTION
Q. 1 (a) Sketch typical output characteristics for a common emitter transistor and illustrate the region where the transistor is said to be saturated. What bias condition exists at the collector-base junction ( VCB ) when a transistor operates in the saturated region? [10 marks] (b) Briefly distinguish between avalanche breakdown and zener breakdown in a reverse-biased pn-junction. [10 marks] (c) With reference to transistor amplifiers, explain what is meant by the term stabilisation of the operating point. [10 marks] (d) Show how the maximum power dissipation curve for a transistor may be drawn on the transistor’s output characteristics. Illustrate the direction of curve displacement if the ambient operating temperature of the device is to be increased. [10 marks]
CHOOSE TWO QUESTIONS FROM Q.2, Q.3, OR Q.4.
Q. 2 (a) Draw the circuit diagram of a simple zener diode voltage regulator and briefly explain how the circuit minimises the effects of supply voltage variations on the load voltage. [8 Marks]
(b) A zener diode has a reverse breakdown voltage of 9.1 V and after this may be
considered to be a linear resistance of 18 Ω.
A simple voltage stabilising circuit using the diode above is to maintain 10V
across a constant 500 Ω load from a nominal 13.5 V supply.
Draw the circuit diagram and calculate the value of series resistor required. [12 Marks] (c) If the supply voltage increases by 20%, calculate; (i) the change in load voltage, (ii) the change in diode power dissipation. [10 Marks]
Q.
I B IC (mA)^ @^ V^ CE equal to
( μ A) 2 V 8 V
The characteristics of an NPN transistor are listed above and may be assumed to be linear over the given range. The transistor is used as a common emitter
amplifier with a resistive load of 1.5 k Ω, a supply voltage of 12 V , and a
quiescent base current of 80 μ A.
(a) Plot the load line on the output characteristics and estimate the quiescent power dissipation in the transistor. [15 Marks]
(b) If the ac input signal is a base current of 80 μ Ap-p about a mean dc value of
80 μ A , and the ac input resistance is 1.6 k Ω , determine the following amplifier
parameters;
(i) the ac current gain, (ii) the ac voltage gain, (iii) ac power gain [15 Marks]
