Download Analogue Electronics Exam - Summer 2006 - Electronic Engineering and more Exams Digital & Analog Electronics in PDF only on Docsity!
Cork Institute of Technology
Bachelor of Engineering (Honours) in Electronic Engineering –
Stage 2
(NFQ – Level 8)
Summer 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) Define the small-signal parameters ‘r (^) e’ and ‘β’ for a bipolar junction transistor. [2 marks]
b) Derive expressions for the voltage gain , circuit input impedance and circuit output impedance of a common emitter amplifier. The amplifier has a load of RL and has no capacitor across the emitter resistor R (^) E. Include a diagram of the small signal equivalent circuit as part of the derivation. [8 marks]
c) For the circuit shown in fig Q1, VCC = 15V, R 1 = 33kΩ , R 2 = 10kΩ , RC = 940Ω , RE = 330Ω , RL=2.2kΩ and β = 200. Calculate the voltage gain , the current gain , the circuit input impedance and the circuit output impedance. [10 marks]
Vin
Vout
RC
V (^) CC
R (^1)
R 2 R (^) E RL
C 1
C (^2)
Fig Q1.
Q2.
a) Explain the term ‘small-signal’ operation as applied to the analysis of amplifier circuits. [4 marks]
b) Define the parameters gm , rd and μ in the case of a field effect transistor. [6 marks]
c) Derive expressions for the voltage gain and output impedance of a common source amplifier. [4 marks]
d) The FET shown in fig Q2 has gm = 4.2mS and μ = 410. Determine the voltage gain, input impedance and output impedance of the circuit. [6 marks]
Fig Q2.
Q6.
a) Derive the equation which shows that the application of negative feedback to an amplifier circuit increases the upper –3dB frequency. Hence explain how the bandwidth of the amplifier is affected by negative feedback. [8 marks]
b) List the other properties of negative feedback not referred to in part (a). [4 marks]
c) An amplifier has a mid-band voltage gain of 50dB and distortion of 4%. The – 3dB points are 100Hz and 20kHz. If negative feedback is used to reduce the gain to 35dB determine the feedback factor, the new value of distortion and the new breakpoints. [8 marks]
Q7.
a) For a DC power supply, define the terms ‘ripple factor’ and ‘regulation’. [4 marks]
b) Draw the circuit diagram of a regulated dual power supply, incorporating monolithic regulators, to provide ± 12 V, 250 mA dc from a mains supply of 220 Vrms. Indicate the minimum voltage rating required of the transformer secondary windings, and the minimum current rating of the diodes. [6 marks]
c) Sketch the anode characteristics of a silicon controlled rectifier (thyristor), and explain its operation. [5 marks]
d) Using the two-transistor analogy, show that a thyristor conducts when current is injected into the gate terminal. [5 marks]
