place label hereconsider this 2-bit ripple down counter. (a) ... state one difference between the...

Pages: 36 Questions: 19 ©Copyright for part(s) of this examination may be held by individuals and/or organisations other than the Tasmanian Qualifications Authority.

PLACE LABEL HERE

Tasmanian Certificate of Education

ADVANCED ELECTRONICS

Senior Secondary

Subject Code: ELT315109

External Assessment

2011

Time: Two Hours

On the basis of your performance in this examination, the examiners will provide results on each of the following criteria taken from the syllabus statement: Criterion 2 Recall and apply information regarding circuits. Criterion 8 Demonstrate knowledge and understanding of electronic concepts. Criterion 9 Use mathematical skills and techniques.

TA

SM

AN

IAN

QU

AL

IFIC

AT

ION

S A

UT

HO

RIT

Y

Advanced Electronics

CANDIDATE INSTRUCTIONS You MUST ensure that you have addressed ALL of the externally assessed criteria on this examination paper. There are THREE sections to this paper. All sections are of equal value. Each section is worth a total of 40 marks. You must answer ALL questions. All answers must be written in the spaces provided on the examination paper. The 2011 Advanced Electronics Information Sheet may be used during the examination. No other written material is allowed into the examination. All written responses must be in English.


SECTION A

Answer ALL questions in this section. This section assesses Criterion 2. Question 1 (a) Complete the following table of resistor values: (2 marks)

1st band 2nd band 3rd band Value

Brown Red Black

Orange White Blue

820 k

(b) Two types of resistor in common use are: carbon film and wire-wound. (i) When would a wire-wound resistor be preferable? (1 mark) .................................................................................................................................... .................................................................................................................................... (ii) At high-frequencies, a simple wire-wound resistor may have undesirable side-effects.

Explain why and give a possible solution. (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................

For Marker

Use Only


Question 2 (a) Compare the construction of a ceramic capacitor with that of a tantalum capacitor. In

what circumstances would each be suitable? (3 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) A 470 pF capacitor is connected in parallel with a 3n3 capacitor. Calculate the total

capacitance of the combination. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


Question 3 (a) What is the fundamental difference in design between a passive filter and an active

filter? (1 mark) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) List two advantages of each type. (2 marks)

Passive Active

I

II

For Marker

Use Only


Question 4 (a) Explain the meaning of the term input impedance. (1 mark) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Should the input impedance for an op amp be high or low? Justify your answer. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (c) Should the output impedance for an op amp be high or low? Justify your answer. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


Question 5 (a) Sketch a circuit diagram for a simple high-pass active filter. (2 marks) (b) Calculate component values which would give a cut-off frequency of 15 kHz for the

filter. (Assume a resistance value of 1k5). (3 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


Question 6 A Schmitt inverter is a useful device for building a clock in a digital circuit. The Schmitt inverter relies on the hysteresis effect in electronics.

(a) Sketch the hysteresis characteristic between

€

Vout and

€

Vx for the Schmitt inverter. (2 marks) (b) The output from the clock above is shown. On the same diagram, show the voltage at

€

Vx as a function of time. (1 mark)

(c) For the values shown above, calculate the time constant of the RC combination and

hence determine an approximate frequency of the clock. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only

€

Vout

€

Vx


Question 7 A block diagram for a JK flip-flop is shown. (a) Complete this table. (1 mark)

J K CLK Q 1 1 1 0

€

↓ (b) Explain the function and the mode of operation of the ‘S’ input. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


Question 8 Consider this 2-bit ripple down counter.

(a) Explain how you can identify this as a down counter. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Explain the function of SW1 in the operation of this circuit. Include the roles of R1 and

X in your description. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

Question 8 continues opposite.

For Marker

Use Only


Question 8 (continued) (c) Complete the timing diagram for A and B for the 2-bit down counter on the previous

page. Assume SW1 is open. (2 marks)

CLK

A

B

(d) What will pushing the switch SW2 do to the circuit? (1 mark) ............................................................................................................................................. ............................................................................................................................................. (e) (i) Why is a counter such as this referred to as a ripple counter? (1 mark) .................................................................................................................................... .................................................................................................................................... (ii) State one difference between the design of a ripple counter and that of a

synchronous counter. (1 mark) .................................................................................................................................... ....................................................................................................................................

For Marker

Use Only


SECTION B

Answer ALL questions in this section. This section assesses Criterion 8. Question 9 Below are two simple amplifier circuits.

(i) (ii) (a) Calculate the voltage gain for each of the circuits. (3 marks) (i) ................................................................................................................................. .................................................................................................................................... .................................................................................................................................... (ii) ................................................................................................................................. .................................................................................................................................... ....................................................................................................................................


For Marker

Use Only


Question 9 (continued) (b) For circuit (ii), explain what would happen if the op amp inverting and non-inverting

inputs were reversed. (ie inverting input grounded). (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (c) There are occasions when it is desirable to run an op amp amplifier from a single-

voltage supply (i.e. supply of 0 -12V for instance). (i) State one advantage and one disadvantage of such a configuration. (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................

Question 9 continues over the page.

For Marker

Use Only


BLANK PAGE


Question 9 (continued) (ii) Sketch an op amp amplifier circuit with a single voltage supply. (3marks)

(iii) Why is capacitive coupling needed in this application? (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................

For Marker

Use Only


Question 10 A hobbyist proposed this circuit for a student’s ‘Anti-Sleep Alarm’. After a time interval of about 30 minutes, a small buzzer sounds. If the RESET button is not pushed in the following 30 minutes, the circuit then switches off the room light and heater (to save wastage of electricity). Note: The proposed circuit appears to have several errors in it. The 4020 is a binary ripple counter. The circuit clock has a frequency of approximately 5 Hz.

(a) What is the role of C1? (1 mark) ............................................................................................................................................. ............................................................................................................................................. (b) Pin 10 of IC2 has a labeling error. Explain. (1 mark) ............................................................................................................................................. .............................................................................................................................................


For Marker

Use Only


Question 10 (continued) (c) What is the function of each of the following? (i) D1 (1 mark) .................................................................................................................................... (ii) D3 (1 mark) .................................................................................................................................... (iii) D4 (1 mark) .................................................................................................................................... (d) What is the role of N1 and N2 and associated components? (1 mark) ............................................................................................................................................. ............................................................................................................................................. (e) What is the purpose of the combination of N3 and N4? (1 mark) ............................................................................................................................................. ............................................................................................................................................. (f) What combination of outputs from the 4020 is required to make PZ1 (the piezo) buzz? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (g) What is the function of the combination of C4, R3 and Pin 11? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


Question 11 This comparator is part of a counting circuit. Light from the lamp falls onto the LDR and when the light beam is interrupted the output from the comparator changes state.

(a) When the light is shining on the LDR, is the LED ON or OFF? Explain why. (3 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

(b) The characteristics of the LDR are shown:

Use these to calculate the value of R3 at the threshold setting. At the threshold, the light intensity is 220 lux. (2 marks)

............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................


For Marker

Use Only


Question 11 (continued) (c) Draw a graph showing the output voltage against the light intensity. (2 marks)

For Marker

Use Only


Question 12 This is the block diagram for a simple digital voltmeter. The display ‘refreshes’ every 0.5 seconds. (a) Which block sets the ‘refresh’ rate? (1 mark) ............................................................................................................................................. (b) What is the purpose of the data latch? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (c) What is the role of the decoder? (1 mark) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (d) What is the role of the AND gate? (2 marks) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................


For Marker

Use Only

ramp generator

pulse generator

trigger pulses

voltage comparator

AND gate

binary counter

data latch

display decoder

Input voltage


Question 12 (continued) (e) (i) What does the ramp generator do? (Refer to top graph.) (1 mark) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (ii) Explain the role of the voltage comparator. Complete the

€

Vout graph above. (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (f) What does the input into the binary counter from the trigger pulses do? (1 mark) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only

Vout

Vinput

Vramp

t

t

Comparator


For Marker

Use Only

SECTION C

Answer ALL questions in this section. This section assesses Criterion 9. Question 13 Consider this resistor array. (a) Calculate the resistance of the parallel combination. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) If the voltage at X is to be 8.0V, calculate the nearest E 12 value of R1 required. (1 mark) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................



Question 13 (continued)

(c) Using the E12 value, show that the actual value of

€

Vx is approximately 7.8V. Give your answer to 3 significant figures. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (d) Calculate the current flow through R1. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (e) If your R1 resistor is rated at

€

14W, will it overheat? Show working. (2 marks)

............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


BLANK PAGE


Question 14 A digital logic circuit is given by:

(a) Write a Boolean expression for this circuit. (1 mark) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Complete a truth table for the circuit. (2 marks)

A B C 0 0 0 1 1 0 1 1

(c) Describe the operation of the circuit. (1 mark) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


Question 15 This series resonant circuit is to have a resonant frequency of 33 kHz.

(a) Sketch a graph of the expected

€

Vout ~ f response curve. On your sketch, indicate

€

Vin and the half-power points and bandwidth. (2 marks)

(b) Calculate the value for the capacitance to give the 33 kHz resonant frequency. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................


For Marker

Use Only


Question 15 (continued)

(c) Find the reactance of the circuit at 32 kHz. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (d) What is the impedance at 32 kHz? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


Question 16 In this question, assume that the input impedance is 100

€

Ω and that the load impedance is 100

€

Ω. The amplifier has a gain of 70 dB.

A sinusoid signal of 5.0 mV (peak) is applied

€

Vin( ). (a) Calculate the output voltage. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Will the output voltage ‘saturate’ (i.e. clip) with this input? (1 mark) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (c) Calculate the rms power delivered to the 100

€

Ω load by this input voltage. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................


For Marker

Use Only


Question 16 (continued) (d) A second stage amplifier with gain 25 dB is added to the first.

Calculate the overall power gain of this 2-stage amplifier. (1 mark) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


Question 17 You MUST show your working for this question. Add

€

AF16 to

€

2510 and express your answer in binary. (3 marks) ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... .......................................................................................................................................................

For Marker

Use Only


Question 18 The school science department has asked your electronics class to design a climate-control system for their glasshouse. The system is to have two sensors (temperature (T) and humidity (H)) and three controls (heater (h), windows (w) and shades (S)). When the temperature is low, the heater is turned on. If the temperature is high and the humidity is low, the shades are closed. If the temperature and humidity are both high, the windows are opened. For sensors: 0 = low, 1 = high; for controls: 0 = off/closed, 1 = on/open (a) Draw a logic table of the required logic controls. (2 marks)

INPUTS OUTPUTS T H h w s

(b) Draw a logic diagram, using NAND gates, for your proposed circuit. (3 marks)

For Marker

Use Only


Question 19 In testing an amplifier, a student obtained the following oscilloscope input and output waveforms. (a) What is the frequency of the signal? (1 mark) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................


For Marker

Use Only

2 µs per cm

2 µs per cm


Question 19 (continued) (b) What is the peak-to-peak voltage of the input signal? (1 mark) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (c) What is the RMS voltage of the input signal? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (d) Calculate the voltage gain of the amplifier being tested. (1 mark) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

For Marker

Use Only


BLANK PAGE


Q

BLANK PAGE

This question paper and any materials associated with this examination (including answer booklets, cover sheets, rough note paper, or information sheets) remain the property of the Tasmanian Qualifications Authority.

ADVANCED ELECTRONICS (ELT315109)

2011 External Examination Information Sheet

Page 1 of 2

TA

SM

AN

IAN

QU

AL

IFIC

AT

ION

S A

UT

HO

RIT

Y

Frequency, period

€

f =1T

Ohm’s Law

€

V = IR,

€

I =VR

, R =VI

Power

€

P =VI , P = I2R, P =V 2

R

Current

€

I =PV

, I =PR

Voltage

€

V = PR

€

V =PI

Resistance

€

R =PI2 , R =

V 2

P

Resistors in series RT = R1 + R2 + R3 + ....

Resistors in parallel 1RT

=1R1

+1R2

+1R3

+ ....

or

€

RT = R1−1 + R2

−1 + R3−1 + ...( )

−1

Capacitors in series 1CT

=1C1

+1C2

+1C3

+ ....

or

€

CT = C1−1 + C2

−1 + C3−1 + ...( )

−1

Capacitors in parallel CT = C1 + C2 + C3 + ....

Inductive reactance XL = 2π f L

Capacitive reactance XC =1

2π f C

RC filter cut off frequency fc =1

2π RC

Impedance ZT = 2R + 2X , X = XL − XC

LC filter resonance

€

f =1

2π LC, C =

1L

. 12πf⎛

⎝ ⎜

⎞

⎠ ⎟

2, L =

1C

. 12πf⎛

⎝ ⎜

⎞

⎠ ⎟

2

RC time constant T RC=

RL time constant TLR

=

of 2

Gain

negative gain for an inverting amplifier

€

G =−VoutVin

or

€

−G = RfRin

for a non-inverting amplifier

€

G =VoutVin

or

€

G = 1+RfRin

or

€

G =Rf + RinRin

Summing Amplifier Gain

€

–VoutR f

=Vin1Rin1

+Vin2Rin2

+Vin3Rin3

or

€

Vout = –RfV1R1

+V2R2

+V3R3

⎛

⎝ ⎜

⎞

⎠ ⎟

Power Gain(dB)

€

G =10log PoutPin

or

€

20 log Vout

Vinprovided Zin = Zload( )

Electromagnetic waves

€

v = fλ, f =vλ

, λ =vf

Peak voltage

€

Vpeak =1.414VRMS

RMS voltage

€

VRMS = 0.707Vpeak

Voltage divider

€

Vout =R2

R1 + R2. Vin

E12 Values 10, 12, 15, 18, 22, 27, 33, 39, 47. 56, 68, 82

Component Information Resistor colour code

Black 0 Brown 1 Red 2 Orange 3 Yellow 4 Green 5 Blue 6 Violet 7 Grey 8 White 9

Capacitor values Picofarad (code) Nanofarad Microfarad

1000 (102) 1 0.001

10000 (103) 10 0.01

100000 (104) 100 0.1

1000 000 (105) 1000 1

First digit

Second digit

Multiplier

Tolerance

place label hereconsider this 2-bit ripple down counter. (a) ... state one difference between the...

Documents