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Pages: 36 Questions: 23 ©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

2010

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.

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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 2010 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 Complete this table of capacitor values: (1 mark)

Code nF

€

µF

0.047 333

1500 Question 2 (a) Complete the following table of resistor values: (1 mark)

3k9

Brown Red Brown

560k (b) A resistor has a colour code given by Blue Grey Brown Gold. Calculate the minimum

possible value of its resistance. (1 mark) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 3 Explain, briefly, what is meant by the following terms as applied to amplifiers: (a) Gain. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Bandwidth. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (c) Positive feedback. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (d) Input impedance. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. /8


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Question 4 A low-pass filter with a cut-off frequency of 100 Hz has an input signal of 5.0 V and variable frequency. At low frequencies, 500 mW of power is delivered from the filter. (a) Sketch a

€

Vout~frequency graph for this filter showing all relevant features. (2 marks)

(b) At the cut-off frequency, what is: (i) The output voltage? (1 mark) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (ii) The output power? (1 mark) .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................

f

Vout

/4


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Question 5 (a) Sketch a circuit diagram for a simple low-pass active filter. (2 marks) (b) Calculate component values to give a cut-off frequency of 100 Hz. [You may assume a

resistance of

€

220Ω]. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 6 (a) Describe how this circuit would function. Include the roles of

€

C1 and

€

R1,

€

R2 and

€

R3. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) On the V~t axes provided, show, to scale, how the voltages at points A and C would

change with time. The voltage at point B is given. Assume that

€

R1 = R2 = R3 =10k . (2 marks)

VB

VA VC

t

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A

C

B


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Question 7 An RC circuit is shown. The input is 5 kHz, 12 V (rms).

(a) Calculate the value of C that makes the voltage across C equal to the voltage across the

resistor. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) What is this rms voltage? (1 mark) ............................................................................................................................................. ............................................................................................................................................. (c) Calculate the peak value of the output voltage. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 8 A digital logic circuit is given by:

(a) Write a Boolean expression for this circuit. (2 marks) (b) Complete a Truth Table for this circuit. (2 marks)

A B Q

BA

A

Q

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Question 9 (a) A block diagram for a J-K flip-flop and the logic table are given:

J K CLK Q 0 0

€

↑ No change

1 0

€

↑ 1

0 1

€

↑ 0

1 1

€

↑ Toggles (i) Explain the difference between synchronous and asynchronous inputs. (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (ii) Which pair J, K or R, S is synchronous and which pair is asynchronous? (1 mark) .................................................................................................................................... .................................................................................................................................... (iii) What do the symbols in the CLK column of the table indicate? (1 mark) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................

Question 9 continues opposite.


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Question 9 (continued) (b) Show how to interconnect the appropriate pins of the JK flip-flop to convert it into a

T-type flip flop and label the inputs. (2 marks)

(c) This circuit using a D-type flip-flop can be used to synchronise a debounced switch with

clock pulses. Complete the timing diagram for the Q and X outputs. (2 marks)

A

CLK

Q

X

A

CLK

X

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SECTION B

Answer ALL questions in this section. This section assesses Criterion 8. Question 10 (a) Calculate the time constant of this RC combination. (1 mark)

............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Calculate the period of a 2.0 kHz square wave. (1 mark)

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


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Question 10 (continued) (c) A 2.0 kHz square wave is fed into each of the following RC circuits as shown. Sketch the expected output waveforms in each case. (i) (2 marks)

Vin

Vout

(ii) (2 marks)

Vin

Vout

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Question 11 The crops in a hot-house are to be protected from low temperatures. The relay in the circuit below will activate a heater when the temperature drops below a certain level.

(a) At what temperature will the relay activate? Show your reasoning. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Sketch a graph to show how the voltage across the relay will change with temperature.

Include a scale. (2 marks)

V T



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Question 11 (continued) (c) How could the circuit be modified to operate a fan if the temperature rises above 40˚C?

Draw your schematic showing component values. (3 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 12 When the power to a counting chip is turned off, the chip may ‘remember’ its previous state. To ensure that the counter starts from zero when turned on again, a switch-on reset can be added. Here a chip used as part of a counting circuit is wired to reset at turn-on.

(a) Is the reset input ‘Active Hi’ or ‘Active Lo’? How can you tell? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Explain how this configuration will reset the chip at turn-on. Include a sketch of the

voltage at reset terminal when SW1 is pushed. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 13 A push button switch to input data to a circuit is shown.

What is the function of the resistor? What would happen if the resistor were not present? (2 marks) ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... .......................................................................................................................................................

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Question 14 A simple Digital-to-Analogue Converter (DAC) is shown. Not all resistor values are given.

The inputs to D, C, B and A can be either +5V or 0V; these can be represented as 1 and 0. The output

€

Vout( ) will reflect the values of those inputs. Each successive input gives rise to double the output voltage. When the input DCBA = 0010 (i.e. +5V at B and 0V at the other inputs), then

€

Vout = –1.6V . (a) Calculate

€

RF . (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................



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Question 14 (continued) (b) Evaluate

€

RA,

€

RC and

€

RD . (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (c) Complete this table. (2 marks)

DCBA

€

Vout (Volts)

0000

0001

0010 –1.6

0101

1000

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Question 15



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Question 15 (continued) Consider the circuit diagram on the opposite page. The circuit is for a digital clock. (It has a plug pack as well as a battery backup.) (a) Examine the power supply. (i) What is the function of D4? (1 mark) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (ii) Inspection of the circuit diagram shows that +V2 powers the display while V1

powers the timing circuit. What is the function of D5? (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (b) ORP12 (attached to 1C4d) is a light dependent resistor whose resistance decreases as the

light intensity increases. Explain how the output from 1C4d changes as the light level changes. (2 marks)

............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (c) In what mode is IC2a operating? (1 mark) ............................................................................................................................................. .............................................................................................................................................

Question 15 continues over the page.


Question 15



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Question 15 (continued) (d) What happens to IC3 when its output pins 12 and 13 are both high? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (e) What is the function of the output from pin 5 of IC5? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 16 You are asked to design a headlight reminder for an older car. A warning LED is to glow if the headlights are left on when the ignition switch is turned off. A small beeper is to sound for 5 seconds. Draw a block diagram to illustrate how you would construct a circuit to solve this problem. (5 marks)

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SECTION C

Answer ALL questions in this section. This section assesses Criterion 9. Question 17 (a) Sketch the following configurations. (1 mark) (i) A 330 nF capacitor in series with a 0.47

€

µF capacitor. (ii) A parallel connection of 270 pF and 0.39 nF capacitors. (b) Calculate the total (resultant) capacitance in each case. (2 marks) (i) ....................................................................................................................................... ............................................................................................................................................. ............................................................................................................................................. (ii) ...................................................................................................................................... .............................................................................................................................................

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Question 18 An LED has the following specifications.

Type Nominal Size (mm) Lens FWD

Voltage

Max Cont Forward Current (mA)

Max. Rev Voltage

Luminous Intensity

(mcd)

@ Current (mA)

Peak Wavelength

(nm)

Red 5 dia Red diffused 2.1 15 5 3 10 697

A red LED is to be used as an indicator and is connected to a 15 V supply.

(a) What will the voltage drop across the LED be when it is glowing? (1 mark) ............................................................................................................................................. (b) What is the maximum current which should be permitted to flow through the LED? (1 mark) ............................................................................................................................................. (c) Calculate the minimum E12 value of the required dropper resistor. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (d) Find the power dissipated in this dropper resistor. (1 mark) ............................................................................................................................................. .............................................................................................................................................

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Question 19 Consider this potential divider.

(a) (i) Calculate the output voltage. (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (ii) Calculate the current flowing through the potential divider. (1 marks) .................................................................................................................................... .................................................................................................................................... If a load is connected to the output, the output voltage drops.

Assuming that the load resistor is 2k: (b) Calculate the resistance of the parallel combination (

€

R2 and

€

Rload). (2 marks) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................



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Question 19 (continued) (c) Calculate the new output voltage. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 20 A series resonant circuit has a resistance of 50

€

Ω, an inductance of 12.5 mH and a capacitance of 3.3 nF.

(a) Calculate the resonant frequency. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) At resonant frequency, what is the impedance of the circuit? (1 mark) ............................................................................................................................................. ............................................................................................................................................. (c) (i) Calculate the reactance of the circuit at 26 kHz. (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (ii) Calculate the impedance at 26 kHz. (2 marks) .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................



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Question 20 (continued) (d) Sketch a graph of

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Vout~f. (1 mark)

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f

Vout


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Question 21 Consider this amplifier. Assume that the input and load impedances are equal.

(a) If an input voltage of 20 mV causes an output voltage of 5.0 V, calculate the power gain

(in dB) of the amplifier. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) What is the (approximate) maximum peak output voltage before distortion occurs? (1 mark) ............................................................................................................................................. (c) Therefore calculate the maximum possible input voltage before distortion. (3 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 22 You must show your working in this question. (a) Convert

€

4410 and

€

A116 to binary. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (b) Express 1 100 010

€

0012 in BCD. (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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Question 23 A As part of a project to set up a traffic light system for road works, an electronics student tested the following circuit. IC1 is a 7-bit binary ripple counter; the outputs Q4 – Q6 are labelled A, B and C respectively.

(a) What is the frequency at output: (2 marks) (i) Q1? .................................................................................................................................... .................................................................................................................................... (ii) Q4? .................................................................................................................................... ....................................................................................................................................


A B

C


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Question 23 (continued) (b) Complete this truth table for one cycle. (2 marks)

C B A Q6 Q5 Q4

RED YELLOW GREEN

0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1

(c) Describe the operation of the yellow light. (1 mark) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (d) For how long will the red light stay on each cycle? (2 marks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

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BLANK PAGE

ADVANCED ELECTRONICS (ELT315109)

2010 External Examination Information Sheet

Page 1 of 1

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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 VoutVin

provided Zin = Zout( )

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

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