Examination Material for Analogue Electronics Unit - Manchester Metropolitan University, Exams of Electrical Engineering

Download Examination Material for Analogue Electronics Unit - Manchester Metropolitan University and more Exams Electrical Engineering in PDF only on Docsity! THE MANCHESTER METROPOLITAN UNIVERSITY FACULTY OF SCIENCE AND ENGINEERING DEPARTMENT OF ENGINEERING AND TECHNOLOGY SESSION 2005/2006 Examination for the BEng (HONS) ELECTRICAL AND ELECTRONIC ENGINEERING HND ELECTRONIC ENGINEERING YEAR ONE UNIT 64EE1102 : ANALOGUE ELECTRONICS Tuesday 2 May 2006 2:00 pm to 4:00 pm Instructions to Candidates Attempt FOUR questions. Marks for each section are shown in parentheses. Candidates are permitted to use their own calculators subject to Faculty Board Examination Procedures and Practices. S125 11/07/2006 1 1. (a) Briefly explain, with the aid of a diagram, the problem of crossover distortion experienced in Class B push-pull amplifiers. [5] (b) (i) Explain, with the aid of a circuit diagram, how the problem of crossover distortion can be overcome using a Class AB amplifier configuration. (ii) Is the Class AB amplifier more or less efficient than a Class B amplifier? Explain your answer. [7] (c) State the maximum theoretical efficiency of a Class B amplifier and a Class A amplifier with a resistive load. [3] (d) For a particular Class B amplifier the dc input power is 50 watts and the efficiency of the amplifier is 60%. The maximum junction temperature of the power transistors is 200 degrees Centigrade and θJC = 2 deg C/W. Determine the maximum thermal resistance of a suitable heatsink, assuming both output power transistors are mounted on the same heatsink and the maximum ambient temperature is 30 degrees Centigrade. [10] S125 11/07/2006 continued 4 4. (a) Integrated MOSFET electrical characteristics can be designed by variations in manufacturing process parameters and MOSFET layout geometry. For each of the following MOSFET Ids vs Vds output characteristic regions : o The cut-off region o The linear region o The saturation region. Explain the electronic operation of an ENHANCEMENT mode MOSFET. (Your explanation should include both appropriate cross-sectional diagrams and equations that incorporate the commonly used terms β, W and L.) [10] (b) For ONE of the following, write an essay describing in detail: (i) A complete mains derived power supply unit incorporating mains switch and filter, mains fuse, bridge rectifier full-wave rectification, filter, 78 series 12 volt supply regulator. [8] How important is the use of a heatsink for the rectifiers or series regulator? [2] (ii) The circuit topology and operation of MOSFET, tri-state binary logic. [10] S125 11/07/2006 continued 5 5. Figure Q5 depicts the trajectories of 6 holes within a vertical, silicon, PNP Bipolar Junction Transistor. Figure Q5 (© Milward 1955) (a) State what is meant by carrier ‘recombination’. [2] (b) State how base width changes BJT operation. [3] (c) State why there is a depression seen in the ‘surface’ around the base terminal. [2] (d) State what is occurring when the base region is energised to the potential depicted by the letters A & B. [2] (e) Sketch an electronic circuit schematic that could provide these bias conditions. [2] (f) Labelling the holes shown (from left to right) numbers 1 to 6 and creating a table to help in your explanation, state the conditions that gave rise to the path taken by holes 1, 2, 4 and 5. [12] (g) If the transistor were manufactured from germanium instead of silicon, explain how appearance of Figure Q5 might change. [2] S125 11/07/2006 END