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DLX2 Autumn 2006 Analogue Electronics Page 1 of 2
Cork Institute of Technology
Bachelor of Engineering (Honours) in Electronic Engineering – Stage 2
(NFQ – Level 8)
Autumn 2006
Analogue Electronics
(Time: 3 Hours)
Answer any 5 questions. Examiners : Mr. P. Collins All questions carry equal marks Mr. M. Cranitch Prof. G. Hurley Dr. S. Foley
Q1.
(a) Draw the circuit diagram for each of the following op-amp circuits (i) 3-input summing amplifier (ii) difference amplifier (iii) integrator (iv) differentiator. [8 marks ]
(b) For the circuit in part(a)(ii) derive an expression for the output voltage. [4 marks ]
(c) For the circuits in part(a)(iii) and part(a)(iv) , sketch the output waveform in each case when the input is a square wave. [8 marks ]
Q2.
(a) Describe what is meant by the term ‘small-signal operation’ and define the small-signal parameters re and β for a bipolar junction transistor. [8 marks ]
(b) Derive expressions for the voltage gain , input and output impedances of a common emitter amplifier , both with and without an emitter bypass capacitor. [12 marks]
Q3. (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 (ii) the common mode gain. Hence show that the CMRR is given by R (^) E/r (^) e. [ 9 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 CMRR. [ 5 marks ]
DLX2 Autumn 2006 Analogue Electronics Page 2 of 2
Q4.
(a) State the criteria required in a circuit for oscillations to occur and be maintained. What are these conditions usually called? [ 6 marks ]
(b) Draw the circuit-diagram of a Wien-bridge oscillator and derive the equation for frequency of operation. [ 8 marks ]
(c) Explain how the amplitude of the output in the circuit in part(b) can be stabilized to ensure that saturation does not occur. [ 6 marks ]
Q5. (a) Define the terms ‘mark space ratio’ and ‘duty cycle’ in relation to a rectangular waveform and the term ‘slope error’ as applied to a sawtooth waveform. [ 6 marks ]
(b) Draw the circuit diagram of a 555 astable multivibrator and a 555 monostable multivibrator. [ 8 marks ]
(c) Determine suitable component values for an astable multivibrator to provide an output signal at 1kHz with a duty cycle of 50%. [ 6 marks ]
Q6. (a) Show , by deriving the relevant equation in each case , that negative feedback in an amplifier circuit leads to a reduction in both voltage gain and distortion. [ 6 marks ]
(b) Using the result for voltage gain obtained in part(a) , derive the equations for voltage gain of (i) a non-inverting op-amp circuit (ii) an op-amp voltage follower. [ 6 marks ]
(c) An amplifier has the following characteristics without feedback : A = 100 , Ri = 10kΩ , Ro = 1kΩ , f (^) L = 200Hz , f (^) H = 50kHz. If voltage-series feedback is applied determine the amplifier characteristics when (i) β = 1% (ii) β = 9%. [ 8 marks ]
Q7. (a) Define the terms ‘ripple factor’ and ‘regulation’ in the case of a power supply. [ 4 marks ]
(b) Draw the circuit diagram of a series voltage regulator. [ 8 marks ]
(c) Draw the circuit diagram of a regulated dual power supply , incorporating monolithic regulators , to provide +/- 12V DC from a mains supply of 220V. The supply should provide 0.5A per o/p. Indicate the minimum VA rating required of the transformer secondary windings. [ 8 marks ]
