Bachelor of Engineering (Honours) in Electronic Engineering Exam: Analogue Electronics, Exams of Digital & Analog Electronics

Download Bachelor of Engineering (Honours) in Electronic Engineering Exam: Analogue Electronics and more Exams Digital & Analog Electronics in PDF only on Docsity! Cork Institute of Technology Bachelor of Engineering (Honours) in Electronic Engineering – Stage 2 (EELXE_8_Y2) Summer 2008 ANALOGUE ELECTRONICS (Time: 3 Hours) Answer five questions [each 20 marks] Maximum available marks: 100 Examiners: Dr. M. Cranitch Prof. G. Hurley Dr. S. Foley Q1. (a) With reference to an op-amp, explain the terms ‘virtual earth’, ‘output offset voltage’ and ‘transition frequency’. In the case of the transition frequency, quote the figure typical of the 741 op-amp. [7 marks] (b) Define the term ‘slew rate’ in relation to an op-amp. Explain with the aid of a circuit diagram and relevant waveforms how this parameter can be measured by means of a laboratory experiment. [7 marks] (c) Sketch time-related input and output waveforms for (i) an op-amp integrator, and (ii) an op-amp differentiator, when a square wave is applied in each case [6 marks] Q2. (a) Explain the terms ‘differential gain’, ‘common-mode gain’ and ‘common-mode rejection ratio (CMRR)’ as applied to a differential amplifier. [6 marks] (b) Draw the circuit diagram of an emitter-coupled differential amplifier with emitter resistance, RE, and derive equations for (i) the differential gain, and (ii) the common-mode gain. Hence show that the CMRR is given by ρ = RE re . [10 marks] (c) Explain the operation of a ‘current mirror’, and indicate how it may be used in place of RE in a differential amplifier to increase the value of the CMRR. [4 marks] 2 Q3. (a) Draw the circuit diagram of each of the following: (i) common collector amplifier, (ii) common drain amplifier, (iii) unity gain non-inverting op-amp circuit. List the three properties which these circuits have in common. [7 marks] (b) Derive expressions for the voltage gain, input impedance and output impedance of the common collector amplifier in part (a)(i). [7 marks] (c) For the circuit in the following diagram Vcc=12V, R1=27 k Ω , R2=4.7 k Ω , RE=1 k Ω , RL=1 k Ω , and β=150. Determine the voltage gain, input and output impedances. [6 marks] Q4. (a) Show, by deriving the relevant equation, that negative feedback in an amplifier circuit leads to a reduction in voltage gain. List the effects of negative feedback on the other parameters of an amplifier. [8 marks] (b) Using the result for voltage gain obtained in part (a), derive equations for the voltage gain of (i) a non-inverting op-amp circuit, and (ii) a voltage follower. [6 marks] (c) An amplifier has the following parameters without feedback: A=120, Ri=10kΩ, RO=1kΩ, fL=200Hz, fH=50kHz. If voltage-series negative feedback is applied, determine the amplifier characteristic when (i) β=1.5%, and (ii) β=7.5%. [6 marks]