# Electrical Technology Grade 12 NSC November 2019 QP (Eng)

> Grade 12 Electrical Technology question paper from the NSC November Exam 2019 (English), 23 pages. Read online or download the free PDF.

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- Updated: 2026-09-27
- Subject: Electrical Technology
- Grade: Grade 12
- Document type: Question paper
- Year: 2019
- Exam period: NSC November Exam
- Curriculum: CAPS
- Pages: 23

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## About this document

Electrical Technology · Grade 12 · NSC November Exam · 2019. Question paper, 23 pages. Read online or download the PDF.

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                                  GRAAD 12

                                   NATIONAL
                              SENIOR CERTIFICATE

                                    GRADE 12

                     ELECTRICAL TECHNOLOGY: ELECTRONICS

                                  NOVEMBER 2019

MARKS: 200

TIME: 3 hours

        This question paper consists of 16 pages, a 1-page formula sheet and
                                 6 answer sheets.

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Electrical Technology: Electronics             2                            DBE/November 2019
                                              NSC

INSTRUCTIONS AND INFORMATION

1.        This question paper consists of FIVE questions.

2.        Answer ALL the questions.

3.        Answer the following questions on the attached ANSWER SHEETS:

          QUESTION 2.3.4
          QUESTION 3.4.3
          QUESTIONS 4.1.2, 4.4.2, 4.6.2 and 4.7.3
          QUESTIONS 5.4.1, 5.4.2, 5.6.4, 5.6.5 and 5.11.4

4.        Write your CENTRE NUMBER and EXAMINATION NUMBER on every
          ANSWER SHEET and hand them in with your ANSWER BOOK, whether you
          have used them or not.

5.        Sketches and diagrams must be large, neat and FULLY LABELLED.

6.        Show ALL calculations and round off answers correctly to TWO decimal
          places.

7.        Number the answers correctly according to the numbering system used in this
          question paper.

8.        You may use a non-programmable calculator.

9.        Calculations must include:

          9.1          Formulae and manipulations where needed

          9.2          Correct replacement of values

          9.3          Correct answer and relevant units where applicable

10.       A formula sheet is attached at the end of this question paper.

11.       Write neatly and legibly.

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Electrical Technology: Electronics                3                           DBE/November 2019
                                                 NSC

QUESTION 1: OCCUPATIONAL HEALTH AND SAFETY
1.1       Describe how teamwork improves work ethics.                                                (2)
1.2       With reference to the Occupational Health and Safety Act, 1993 (Act 85 of
          1993):
          1.2.1        State TWO purposes of the Occupational Health and Safety Act,
                       1993 (Act 85 of 1993).                                                        (2)
          1.2.2        Define the term workplace.                                                    (2)
1.3       An employer has a duty to report on occupational health and safety and
          related matters. Name ONE person they should inform when:
          1.3.1        The allocated task is hazardous                                               (1)
          1.3.2        A major incident occurs                                                       (1)
1.4       State TWO general emergency procedures to be followed when the
          emergency siren is sounded at school.                                                      (2)
                                                                                                     [10]
QUESTION 2: RLC CIRCUITS
2.1       Define the following with reference to RLC circuits:
          2.1.1        Power factor                                                                  (2)
          2.1.2        Q-factor of an inductor in a resonant circuit                                 (2)
2.2       State TWO applications of RLC circuits.                                                    (2)
2.3       FIGURE 2.3 below shows an RLC series circuit. Answer the questions that
          follow.

                                          R            L               C

                                     VR = 12 V      VL = 16 V     VC = 24 V

                               IT = 3 A

                                                       60 Hz

                                     FIGURE 2.3: RLC SERIES CIRCUIT
          Given:
          IT      =   3A
          VR      =   12 V
          VL      =   16 V
          VC      =   24 V
          f       =   60 Hz

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Electrical Technology: Electronics                 4                           DBE/November 2019
                                                  NSC

          2.3.1         Calculate the total voltage of the supply.                                    (3)

          2.3.2         Calculate the value of the inductive reactance.                               (3)

          2.3.3         State if the circuit is capacitive or inductive. Motivate your answer.        (2)

          2.3.4         Complete the phasor diagram on the ANSWER SHEET for
                        QUESTION 2.3.4 and show the direction of rotation.                            (4)

          2.3.5         Describe how an increase in impedance, while keeping the
                        resistance constant, will affect the phase angle and the power
                        factor.                                                                       (2)

2.4       FIGURE 2.4 below shows an RLC parallel circuit consisting of a 20 Ω resistor,
          an inductor with an inductive reactance of 30 Ω and a capacitor with a
          capacitive reactance of 40 Ω, all connected across a 120 V/60 Hz supply.
          Answer the questions that follow.

                                         IT

                                               IR = 6 A       IL = 4 A           IC = 3 A

            120 V                              R = 20 Ω        XL = 30 Ω           XC = 40 Ω
            60 Hz

                                     FIGURE 2.4: RLC PARALLEL CIRCUIT

          Given:

          R        =    20 Ω
          XL       =    30 Ω
          XC       =    40 Ω
          VT       =    120 V
          f        =    60 Hz

          2.4.1         Calculate the total current in the circuit.                                   (3)

          2.4.2         Calculate the phase angle.                                                    (3)

          2.4.3         State whether the phase angle is leading or lagging. Motivate your
                        answer.                                                                       (2)

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Electrical Technology: Electronics               5                          DBE/November 2019
                                                NSC

2.5       FIGURE 2.5 below shows an RLC series resonant circuit which consists of a
          12 Ω resistor, an inductor with an inductive reactance of 50 Ω and a variable
          capacitor, all connected across a 120 V/2 kHz supply. Answer the questions
          that follow.

                                R = 12 Ω          XL = 50 Ω            C

                                                 120 V/2 kHz
                           FIGURE 2.5: RLC SERIES RESONANT CIRCUIT

          Given:

          VT      =   120 V
          f       =   2 kHz
          R       =   12 Ω
          XL      =   50 Ω

          2.5.1        Calculate the value of C when the circuit resonates at 2 kHz.               (4)

          2.5.2        Calculate the value of the current in the circuit.                          (4)

          2.5.3        State how current will be affected if the value of the resistance is
                       doubled.                                                                    (1)

          2.5.4        List THREE characteristics of an RLC series circuit at resonance.           (3)
                                                                                                   [40]

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Electrical Technology: Electronics              6                          DBE/November 2019
                                               NSC

QUESTION 3: SEMICONDUCTOR DEVICES
3.1       Name the type of material used for the gate terminal in a P-channel JFET.                   (1)
3.2       Draw a neatly labelled symbol of an N-channel JFET.                                         (3)
3.3       Study the symbol in FIGURE 3.3 below and answer the questions that follow.

                                                         D

                                           G

                                                         S

                              FIGURE 3.3: FIELD-EFFECT TRANSISTOR
          3.3.1        State whether the field-effect transistor (FET) in FIGURE 3.3 is
                       a P-channel or an N-channel.                                                   (1)
          3.3.2        List THREE conditions for the correct biasing of the transistor in
                       FIGURE 3.3.                                                                    (3)
3.4       Refer to FIGURE 3.4 below and answer the questions that follow.

                                                                                            t
                                     R1                      R2
                                                                  VB2

                                                     E            B2

            VC
                                                                  B1
                                     C
                                                             R3

                          FIGURE 3.4: UJT AS A SAWTOOTH GENERATOR
          3.4.1        Besides a sawtooth generator, name ONE other application of
                       a UJT.                                                                         (1)
          3.4.2        Explain what causes the UJT to trigger ON in the circuit.                      (2)
          3.4.3        Draw the output waveform between points B1 and ground on the
                       ANSWER SHEET for QUESTION 3.4.3.                                               (3)

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                                                     NSC

3.5       Refer to FIGURE 3.5 below and answer the questions that follow.

                                                      741

                                             FIGURE 3.5: 741 OP-AMP

          3.5.1        State how you would identify pin 1 of the IC in FIGURE 3.5.                     (1)

          3.5.2        List the THREE stages into which the internal circuit of the op-amp
                       is divided.                                                                     (3)

3.6       FIGURE 3.6 below shows the op-amp as an inverting amplifier. Answer the
          questions that follow.

                                                     RF = 100 kΩ

                                                               +15 V            V
            2V                        RIN = 12 kΩ
                                                           _
                            t
                                                                                              t
                                VIN                        +            VOUT
                                                0V             -15 V

                                         FIGURE 3.6: INVERTING OP-AMP

          Given:

          VIN =        2V
          RF =         100 kΩ
          RIN =        12 kΩ

          3.6.1        Calculate the output voltage based on the data in FIGURE 3.6.                   (3)

          3.6.2        Explain why the shape of the output waveform is NOT an exact
                       replica of the input waveform.                                                  (2)

          3.6.3        Identify the maximum output voltages (Vout).                                    (2)

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Electrical Technology: Electronics              8                        DBE/November 2019
                                               NSC

3.7       Refer to the data sheet in FIGURE 3.7 below and answer the questions that
          follow.

                                      FIGURE 3.7: DATA SHEET
          3.7.1        Rewrite the abbreviation DIP in full.                                    (1)
          3.7.2        Write down the maximum supply voltage for the NE555 IC.                  (1)
          3.7.3        Identify the typical trigger voltage of the NE555 IC, in the data
                       sheet above, when the supply voltage is +15 V.                           (1)
3.8       Explain what will happen to the output of an NE555 IC when the trigger
          voltage rises above the threshold voltage level of 10 V.                              (2)
                                                                                                [30]

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Electrical Technology: Electronics                   9                                    DBE/November 2019
                                                    NSC

QUESTION 4: SWITCHING CIRCUITS
4.1       Refer to FIGURE 4.1 below and answer the questions that follow.

                        Input                 Multivibrator                          Output

                                                                                                     +Vout

              T1                                   A
                                                                             -Vout
                           T2                                                        T1    T2

                                                                                                   +Vout

                                                   B
                   T1                                                        -Vout
                                                                                     T1

                                               Astable
              No input signal                                                C
                                              Multivibrator

                                       FIGURE 4.1: MULTIVIBRATORS
          4.1.1             Identify multivibrators A and B.                                                       (2)
          4.1.2             Draw the output signal of the astable multivibrator at C on the
                            ANSWER SHEET for QUESTION 4.1.2.                                                       (2)
4.2       Refer to the circuit in FIGURE 4.2 below and answer the questions that follow.
                                           +6V

                     R1             R2
                    10 kΩ          10 kΩ
                                                                          R3
                                                             8           330 Ω
                                                     4
                                                     7   555         3
                                                     6
                                                     2
                                                         1       5
                         S1        S2
                         Set       Reset                                                  LED
                                                                      C2
                                                                     10 nF

                                  FIGURE 4.2: BISTABLE MULTIVIBRATOR
          4.2.1             State the function of R1 and R2.                                                       (2)
          4.2.2             Describe what happens when the set switch, S1, is pressed.                             (3)
          4.2.3             Explain why threshold pin 6 is connected directly to ground.                           (3)

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Electrical Technology: Electronics                      10                           DBE/November 2019
                                                       NSC

4.3       Refer to FIGURE 4.3 below and answer the questions that follow.

                                                                             Upper
                                                                             trigger level

                            Input           V
                                                                              t

                                                                             Lower
                                                                             trigger level

                                         +VCC

                          Output            V
                                                                              t

                                         -VCC

                       FIGURE 4.3: SCHMITT TRIGGER INPUT AND OUTPUT
          4.3.1        State whether the output signal represents an inverting or
                       a non-inverting Schmitt trigger. Motivate your answer.                                   (3)
          4.3.2        Draw the circuit diagram of the Schmitt trigger consisting of two
                       resistors and a 741 op-amp that will produce the output signal in
                       FIGURE 4.3.                                                                              (7)
4.4       Refer to FIGURE 4.4 below and answer the questions that follow.

                                                +V

                                                               R1
                                                                             +V
                  V VIN
                                                VIN
                                     VREF                                   741                 VOUT

                  0
                                     t                                       -V
                                                               R2

                               FIGURE 4.4: OP-AMP CIRCUIT DIAGRAM
          4.4.1        Identify the op-amp circuit diagram in FIGURE 4.4.                                       (2)
          4.4.2        Draw the output                signal    on   the   ANSWER       SHEET          for
                       QUESTION 4.4.2                                                                           (4)
          4.4.3        Explain how the reference voltage is made negative.                                      (2)

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Electrical Technology: Electronics                    11                       DBE/November 2019
                                                     NSC

4.5       Refer to FIGURE 4.5 below and answer the questions that follow.

                                          R1 20 kΩ              RF 100 kΩ
                    300 mV

                                          R2 20 kΩ                  +10 V
               V1          500 mV
                                                                -

                     V2                   R3 20 kΩ              +
                                 400 mV                                                    VOUT
                                                                    -10 V
                            V3

                                                                                      0V

                             FIGURE 4.5: INVERTING SUMMING AMPLIFIER

          Given:

          V1    =     300 mV
          V2    =     500 mV
          V3    =     400 mV
          RF    =     100 kΩ

          R1 = R2 = R3 = 20 kΩ

          4.5.1           Explain how the gain of this amplifier can be determined.                      (3)

          4.5.2           Calculate the output voltage of the amplifier.                                 (3)

          4.5.3           Give a reason why the amplifier is NOT saturated.                              (2)

          4.5.4           Calculate the gain of the amplifier using voltage values.                      (3)

          4.5.5           Explain the advantage of using a variable resistor in the feedback
                          loop instead of a fixed resistor.                                              (2)

          4.5.6           Describe what will happen to the output voltage if the value of R 2
                          is changed to 10 kΩ.                                                           (2)

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                                                      NSC

4.6       Refer to FIGURE 4.6 below and answer the questions that follow.

                                                                 C

                        +V
                                                                         R          Output
              Input
                         0
                                                       t

                                     FIGURE 4.6: CIRCUIT DIAGRAM
          4.6.1        Identify the circuit diagram in FIGURE 4.6.                                     (2)
          4.6.2        Draw the output signal on the ANSWER                     SHEET        for
                       QUESTION 4.6.2 for the given circuit time constant.                             (3)
          4.6.3        Explain how the output will be affected if the circuit time constant is
                       increased.                                                                      (2)
4.7       Refer to FIGURE 4.7 below and answer the questions that follow.

                                                 IF         CF

                                     RIN                    +V
                         IIN
                                                                             VOUT

                                                            -V

                        FIGURE 4.7: OP-AMP AS INVERTING INTEGRATOR
          4.7.1        State the purpose of CF.                                                        (1)
          4.7.2        Name THREE key operating points of the circuit in FIGURE 4.7.                   (3)
          4.7.3        Draw the output signal on the ANSWER SHEET                            for
                       QUESTION 4.7.3 if the signal below is applied to the input.

                                           VIN

                                            0
                                                                     t
                                     FIGURE 4.7.3: APPLIED SIGNAL                                      (4)
                                                                                                       [60]

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Electrical Technology: Electronics                            13                                 DBE/November 2019
                                                             NSC

QUESTION 5: AMPLIFIERS
5.1       Compare Class A and Class B amplifiers with reference to the following:
          5.1.1           Q-point                                                                                       (2)
          5.1.2           Efficiency                                                                                    (2)
5.2       Refer to FIGURE 5.2 below and answer the questions that follow.

             IC                                                                                     VCC = 12 V
                   (mA)
             15
                                                                           RC = 800 Ω
             12
                                       Q- point                              S1
               9
                                                                                           Q1
               6

               3

                     2         4   6       8       10   12    VCE                                    0V
                     FIGURE 5.2 A : DC LOADLINE                       FIGURE 5.2B: BIASED TRANSISTOR

                                    FIGURE 5.2: TRANSISTOR AMPLIFIER
          5.2.1           State ONE function of the collector resistor in FIGURE 5.2B.                                  (1)
          5.2.2           Explain how VCE becomes equivalent to VCC when S1 is open.                                    (2)
5.3       With reference to biasing, explain Class C amplification.                                                     (2)
5.4       Refer to FIGURE 5.4 below and draw the output waveforms on the ANSWER
          SHEET for QUESTION 5.4 when the transistor is operating as the following:

                                                                    +VCC

                                                              R

                                   360°
                                   input                               NPN
                          +V
                                                                    transistor          output

                                               t
                          -V

                                   FIGURE 5.4: BIASED NPN TRANSISTOR
          5.4.1           Class A amplifier                                                                             (3)
          5.4.2           Class AB amplifier                                                                            (3)

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Electrical Technology: Electronics                    14                       DBE/November 2019
                                                     NSC

5.5       State ONE undesirable condition that may occur due to the incorrect biasing
          of a transistor.                                                                            (1)

5.6       Refer to FIGURE 5.6 below and answer the questions that follow.

                                         +VCC
                                         A                                        D

                                                           R1   RC
                                                                 G
                                                                                  E
                                                                     C2
                                         B                      T1
                                                C1
               +V

                0
                                     t                                    CE
                                                           R2   RE
                -V

                                         C                                        F

                             FIGURE 5.6: COMMON EMITTER AMPLIFIER

          5.6.1        Explain why the circuit is called a common emitter amplifier.                  (2)

          5.6.2        Name the points where the input signal and the load will be
                       connected.                                                                     (2)

          5.6.3        Identify the TWO components that protect the transistor from
                       thermal runaway.                                                               (2)

          5.6.4        Draw the waveform that would appear between points G and F on
                       the ANSWER SHEET for QUESTION 5.6.4.                                           (3)

          5.6.5        Draw the output waveform that would appear between points E
                       and F on the ANSWER SHEET for QUESTION 5.6.5.                                  (3)

5.7       Give TWO reasons for using coupling methods in amplifier circuits.                          (2)

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                                                NSC

5.8       A push-pull amplifier circuit has the following information:
          Given:
          Input power                = 3 015 watts
          Output power               = 1 200 watts
          Input voltage              = 230 V
          Output voltage             = 219 V
          Output current             = 5,48 A
          Output impedance           = 40 Ω
          Calculate the following:
          5.8.1        Power gain in dB                                                                (3)
          5.8.2        Voltage gain in dB                                                              (3)
5.9       Define the term gain of an amplifier.                                                        (2)
5.10      A certain cascaded amplifier (three-stage amplifier) arrangement has the
          following voltage gain:
          AV1= 10, AV2= 15 and AV3= 20.
          Calculate the total voltage gain.                                                            (3)
5.11     Refer to the amplifier circuit diagram in FIGURE 5.11 below and answer the
         questions that follow.

                                                         +Vcc

                                      R1
                                                           Q1
                                                          NPN

                                      R2
                                                                C

                                      R3
                        AC
                                                          Q2
                                                         PNP

                                      R4

                             FIGURE 5.11: AMPLIFIER CIRCUIT DIAGRAM
          5.11.1       Identify the circuit diagram in FIGURE 5.11.                                    (2)
          5.11.2       Explain how cross-over distortion is eliminated in this amplifier.              (2)
          5.11.3       State the purpose of the resistors in the circuit diagram.                      (1)
          5.11.4       Draw a fully labelled output waveform of the circuit diagram on the
                       ANSWER SHEET for QUESTION 5.11.4.                                               (3)
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                                                   NSC

5.12     FIGURE 5.12 below shows an FET oscillator circuit diagram. Answer the
         questions that follow.

                                                         +VCC

                                              R2
                                                                     C5
                                                                          VOUT
                     C3
                                                         Q1

                                R1
                                                                C4
                                              R3

                                          L                          C6

                                     C1        C2

               FIGURE 5.12: COLPITTS OSCILLATOR USING FET TRANSISTOR

         Compare the differences between RC and LC oscillators with reference to
         the following:

         5.12.1      Feedback circuit                                                     (2)

         5.12.2      Oscillation frequency                                                (2)

5.13     Draw a modified tank circuit to change the Colpitts oscillator in FIGURE 5.12
         into a Hartley oscillator.                                                       (3)

5.14     Name TWO functions of transistor Q1 in FIGURE 5.12.                              (2)

5.15     Name TWO similarities between an LC oscillator and an RC oscillator.             (2)
                                                                                          [60]

                                                                                 TOTAL:   200

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Electrical Technology: Electronics                                                        DBE/November 2019
                                                          NSC

                                                  FORMULA SHEET
RLC CIRCUITS                                            SEMICONDUCTOR DEVICES
P  V  I  cos θ                                                 V          RF 
                                                        Gain A V  OUT         
XL  2 fL                                                         VIN       R IN 
          1                                                            R 
XC                                                     VOUT  VIN    F 
        2 fC                                                          R IN 
            1
fr                                                                      R 
   2 LC                                                VOUT  VIN  1  F 
     f                                                                   R IN 
BW  r
     Q                                                  SWITCHING CIRCUITS
Series                                                             R        R            R 
                                                        VOUT    V1 F  V2 F  ...VN F 
VR  I R                                                           R1        R2          RN 
VL  I XL                                                             V           VOUT
                                                        Gain A V  OUT 
VC  I XC                                                              VIN  V1  V2  ...VN 
       VT                                               VOUT   (V1  V2  ...VN )
IT                 OR        IT  IR  IC  IL
       Z                                                AMPLIFIERS
                                                            V
Z  R 2  X L  X C                                   IC  C
                              2

                                                            RC
VT  VR  VL  VC                          VT  I Z   VCC  VCE  ICRC
                2                 2
                                      OR
            R                               VR                 VOUT
Cos θ               OR           Cos θ                AV 
            Z                               VT                  VIN
       XL X C VL VC 1 L                                       I
Q                                                  A I  OUT
       Z   Z   VT VT R C                                        IIN
Parallel
                                                        A = β1 x β 2         OR       A V  A V1  A V2  A V3
VT  VR  VL  VC
       VT                                               PIN  I2  ZIN
IR 
       R                                                POUT  I2  Z OUT
     VT
IC                                                     GAIN IN DECIBELS
    XC
    V                                                                  I
IL  T                                                  A I  20 log10 OUT
    XL                                                                   IIN
                                                                         V
IT  IR  IL  IC                                     A V  20 log10 OUT
            2             2
                                                                           VIN
       VT                                                              P
Z                                                      A P  10 log10 OUT
       IT                                                                PIN
       I
Cos θ  R
       IT
       XL X C IL IC 1 L
Q            
       Z   Z  IT IT R C

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                                           NSC

CENTRE NUMBER:

EXAMINATION NUMBER:

ANSWER SHEET

QUESTION 2: RLC CIRCUITS

2.3.4          VL = 16 V

                                     VR = 12 V

                                                 IT = 3 A

                                                                 Transfer mark to
                                                                 answer book

               VC = 24 V
                                                                             MOD

                                         FIGURE 2.3.4                                    (4)

QUESTION 3: SEMICONDUCTOR DEVICES

3.4.3             VC

              Input

                  0
                                                            t

                                                                 Transfer mark to
                                                                 answer book
            Output

                                                            t                MOD

                                         FIGURE 3.4.3                                    (3)

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                                               NSC

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EXAMINATION NUMBER:

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QUESTION 4: SWITCHING CIRCUITS

4.1.2
                         +V

                                                               Transfer mark to
                          0                                    answer book
                                                          t

                         +V                                                MOD

                                           FIGURE 4.1.2                                (2)

4.4.2                    V           VIN
                                           VREF

                         0
                                           t

                       +V

                         0
                                               t               Transfer mark to
                                                               answer book

                       -V
                                                                           MOD

                                           FIGURE 4.4.2                                (4)

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4.6.2                     +V

               Input
                           0
                                            t
                          +V

                                                        Transfer mark to
                           0                            answer book
              Output                        t

                          -V                                        MOD

                                     FIGURE 4.6.2                               (3)

4.7.3                   VIN

                           0
                                            t
                       label
                                            t
                                                        Transfer mark to
                                                        answer book
                                                VOUT
                       label

                                                                    MOD

                                     FIGURE 4.7.3                               (4)

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QUESTION 5: AMPLIFIERS

5.4.1

                +V

                  0
                                               t

                                                     Transfer mark to
                                                     answer book

                 -V
                                                                 MOD

                                     FIGURE 5.4.1                            (3)

5.4.2

                 +V

                  0
                                               t
                                                     Transfer mark to
                                                     answer book

                 -V
                                                                 MOD

                                     FIGURE 5.4.2                            (3)

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5.6.4                Input
                             0
                                                            t

                         +V

               DC offset
                 OR
               Q-point
                                                                 Transfer mark to
                                                                 answer book

                                 0
                                                    t                        MOD

                                     FIGURE 5.6.4                                        (3)

5.6.5                Input
                        0
                                                        t

                       +V

                         0
                                                t                Transfer mark to
                                                                 answer book

                       -V                                                    MOD

                                     FIGURE 5.6.5                                        (3)

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5.11.4       Input
                     0
                                                t

                 +V

                     0
                                                    t    Transfer mark to
                                                         answer book

                 -V
                                                                     MOD

                                     FIGURE 5.11.4                          (3)

Copyright reserved

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