AM Demodulator - Analogue Electronics - Exam, Exams of Digital & Analog Electronics

Download AM Demodulator - Analogue Electronics - Exam and more Exams Digital & Analog Electronics in PDF only on Docsity! Cork Institute of Technology Higher Certificate in Engineering in Electronic Engineering-Award (National Certificate in Engineering in Electronic Engineering – Award) (NFQ Level 6) Summer 2005 Analogue Electronics (Time: 3Hours) Instructions Answer Question 1 [28 marks] and any four other questions [Each 18 marks]. Maximum available marks is 100. . Examiner: Mr. T.Connolly Mr. J. Berry Dr. R. O Dubhghaill Q1. (a) Draw circuit diagrams for each of the following: (i) op-amp integrator. (ii) 3 input-summing amplifier. (iii) Emitter Follower (iv) non-inverting op-amp amplifier. (v) op-amp. peak detector [10marks] (b) Draw the circuit diagram of an AM demodulator. Explain in detail the operation of the circuit. [10marks] (c) Draw a circuit diagram of a series transistor voltage regulator. Compare and contrast this with the simple zener diode regulator. [8marks] Q2. (a) List the properties of negative feedback.(N.F.B). [5marks] (b) Derive the formula relating the gain A without N.F.B. to the gain Af when N.F.B. is applied. [9marks] (c) An amplifier has a gain of 60dB and a 4% distortion before N.F.B. is applied. Calculate the gain and percentage distortion when 2% N.F.B. is applied. [4 marks] Q3. (a) Compare A.M. and F.M. in terms of the following: (i) Bandwidth (ii) Ease of demodulation (iii) S/N ratio. [3marks] (b) Draw suitable waveforms to illustrate A.M. and show how the depth of modulation m can be obtained using the waveforms. [5marks] 2 (c) Draw the block diagram of an A.M. superheterodyne receiver and briefly explain the function of each block. [8marks] (d) For A.M. explain the term Image Frequency (I.F.). If the I.F.frequency is 470 kHz and the wanted carrier frequency is 1000KHz, calculate the image frequency. [2marks] Q4. (a) Explain how a black and white T.V.signal is produced. [6marks] (b) Draw the waveform of a single line of a typical video waveform. State the timings. [5marks] (c) How is the colour information inserted into the video signal? [3marks] (d) Draw the frequency response of a typical vestigal sideband television channel. [4marks] Q5. (a) Draw the small signal equivalent circuit of a bi-polar transistor. Explain each component in the circuit. [4marks] (b) Draw the circuit diagram of a common emitter AMP with N.F.B. [3marks] (c) Draw the small signal equivalent circuit of the amplifier in part (b). [3marks] (d) Using the circuit in part (c), derive the equations for input resistance and voltage gain of the circuit in part (b). [8marks] Q6. (a) Name two types of transmission lines. [2marks] (b) List and explain all the coefficients of a transmission line. [8marks] (c) A transmission line with chacteristic impedience 50 ohms is terminated in a load of 75 ohms. Calculate: (i) The voltage reflection coefficient (ii) The voltage standing wave ratio. (iii) Draw the standing wave pattern for the last wavelength of the line connected to the load if the incident voltage is 150V [8marks] Q7. (a) Draw the circuit diagram of a 555 astable multivibrator. [5marks] (b) Using suitable time related waveforms, explain the operation of the circuit [10 marks] (c) Calculate suitable value components if the output frequency is 10kHz with a mark space ratio of 3:2. [3marks]