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Professor Miller, Manchester Metropolitan University, Electrical Engineering, Advanced Electronic Techniques, 2000 2001 Exam, operational amplifier, sinusoidal signal generator, Logic Square Wave Generator, 555 timer.
Typology: Exams
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Exam ination for th e BSc CO MBINED H O NO UR S STA GE TH R EE
Tuesday 15 May 2001
9 .30 am to 12.30 pm
Instructions to Candidates
A nsw er any FIVE questions.
A llquestions carry equalm ark s.
Mark s b reak dow n for individualquestions are sh ow n in parenth eses.
Figure Q 1
(b ) For each circuit, describ e h ow th ese functions are perform ed. State th e criteria th at w ould be used to select com ponent values for th e design of th e w h ole circuit. [8]
(c) State a possib le disadvantage of th is circuit. D raw th e circuit diagram of an alternative circuit th at perform s th e sam e function but overcom es th is disadvantage. Briefly explain its m ode of operation. [9 ]
(c) Th e defining equations for resistance (R ), inductance (L), capacitance (C) and frequency (f), are given as
di dt
dv dt
= f t
Use dim ensionalanalysis and th ese equations to deduce th e dim ensions of each of th ese expressions. Th e term s 2 and π can b e considered dim ensionless.
C fC
2 π
2 πfLI
[10]
vin v
4 (a) State th e purpose of th e m easuring circuit in Figure Q 4. D e scrib e , w ith th e aid of voltage and logic w aveform s, h ow th e m easurem ent is ach ieved. [10]
(b ) A nalyse th e circuit to derive an expression for th e digitalreadout in term s of th e circuit param eters. Com m ent on th e factors influencing th e perform ance of th is m eter. [10]
(b ) W h y are current m irrors w idely used in integrated circuits? [4]
(c) D raw th e circuit diagram of a long-tailed pair am plifier w h ich incorporates th e current m irror describ e d previously. [5]
(d) W h y is a current m irror used in conjunction w ith a long-tailed pair instead of a single resistor? [3]
Vc
Latch enable
Mono
ck
Decoder to give o/p pulse at count = 99
Q Integrator Comparator
Vo
G (^) Vref
Vin fc
Decoder drivers
Decade counters
Latches
Figure Q
(a) Briefly describ e th e operation of th e circuit if th e inputvoltage, Vi, is alw ays positive. [12]
(b ) D raw th e output ch aracteristic, Vo, against th e input voltage, Vi, if th e inputvoltage ranges from 0V to a m axim um of + 3V. [6]
(c) W h at is th e m ain practicaldraw b ack of th is circuit? [2]
(a) Com pare and state th e advantages and disadvantages of th e 555 w ith th e 556. [4]
(b ) D raw th e circuit of a true square w ave oscillator using a 555 and briefly describ e its operation togeth er w ith th e equation for oscillation and duty cycle (D ). [14]
(c) H ow is th e circuit m ore flexib le th an th e sim ple 555 astab le circuit? [2]
Vi
D 1
Figure Q
