Confidential
GRAAD 12
NATIONAL
SENIOR CERTIFICATE
GRADE 12
ELECTRICAL TECHNOLOGY: ELECTRONICS
NOVEMBER 2025
MARKS: 200
TIME: 3 hours
This question paper consists of 25 pages, a 2-page formula sheet and
a 6-page answer sheet.
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Electrical Technology Grade 12 NSC November 2025 QP (Eng)
Grade 12 Electrical Technology question paper from the NSC November Exam 2025 (English), 33 pages. Read online or download the free PDF.
Electrical Technology · Grade 12 · NSC November Exam · 2025. Question paper, 33 pages. Read online or download the PDF.
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- Electrical Technology
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- Grade 12
- Document type
- Question paper
- Year
- 2025
- Exam period
- NSC November Exam
- Curriculum
- CAPS
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Electrical Technology: Electronics 2 DBE/November 2025
NSC Confidential
INSTRUCTIONS AND INFORMATION
1. This question paper consists of SIX questions.
2. Answer ALL the questions.
3. Answer the following questions on the attached ANSWER SHEETS:
QUESTIONS 4.2, 4.5 and 4.11
QUESTIONS 5.2.3, 5.3.2, 5.3.4 and 5.4.4
QUESTION 6.3.5
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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QUESTION 1: MULTIPLE-CHOICE QUESTIONS 2025
Various options are provided as possible answers to the following questions. Choose
the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.15) in
the ANSWER BOOK, e.g. 1.16 D.
1.1 A/An … provides work for another person and remunerates that person.
A employee
B employer
C supervisor
D health and safety representative (1)
1.2 The phase difference between the voltage across the capacitor and the voltage
across the resistor in an RC series circuit is …
A 0°
B 90°
C 120°
D 180° (1)
1.3 In an RLC series circuit, the total current lags the supply voltage. This is an
indication that the frequency is … resonance.
A below
B equal to
C above (1)
1.4 The total impedance in an RLC parallel circuit with a variable frequency supply
is equal to the … at resonance.
A inductive reactance
B capacitive reactance
C resistance (1)
1.5 The advantage of a field-effect transistor is that …
A it has a high input resistance.
B it has a low input resistance.
C it draws a high current from a circuit to which it is coupled.
D None of the above-mentioned (1)
1.6 The … is one of the UJT characteristic operating regions.
A emitter region
B positive resistance region
C forward region
D negative resistance region (1)
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1.7 The … controls the closed-loop gain of an operational amplifier circuit.
A power supply voltage
B internal structure of the op amp
C components in the feedback network
D type of input signal applied (1)
1.8 The voltage that must be applied on pin 2 to allow the output of 555 IC to go
'low' is …
A 1/3 of the supply voltage.
B 2/3 of the supply voltage.
C less than 1/3 of the supply voltage.
D greater than 2/3 of the supply voltage. (1)
1.9 The … produces one pulse cycle of high and low when a trigger pulse is applied
to its input.
A astable multivibrator
B monostable multivibrator
C bistable multivibrator
D comparator (1)
1.10 The following output signal produced by an op amp astable multivibrator has a
duty cycle of … when t1 = t2.
A 25%
B 50%
C 75%
D 100% (1)
1.11 The … is used to recover a signal after it has suffered severe distortion.
A inverting comparator
B op amp differentiator
C Schmitt trigger
D summing amplifier (1)
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1.12 The following is/are key in the operation of an op amp integrator circuit:
A The inputs of the op amp draw zero current.
B The two inputs of the op amp are viewed as both always possessing the
same voltage.
C When a constant current is fed to the capacitor, it will charge at a constant
fixed rate.
D All the above-mentioned (1)
1.13 A … amplifier has a conduction angle of less than 180⁰ of the input cycle.
A class A
B class B
C class AB
D class C (1)
1.14 Identify the oscillator that is used in signal generators above 1 MHz because of
good frequency stability:
A Hartley
B Colpitts
C RC phase-shift (1)
1.15 When the voltage gain of an amplifier is increased, the bandwidth …
A is not affected.
B increases.
C decreases.
D becomes distorted. (1)
[15]
QUESTION 2: OCCUPATIONAL HEALTH AND SAFETY
2.1 Explain machinery with reference to the Occupational Health and Safety Act,
1993 (Act 85 of 1993). (2)
2.2 State TWO precautionary measures to protect yourself when assisting
someone that has been electrocuted. (2)
2.3 Give TWO examples of dangerous practices in the electrical workshop. (2)
2.4 Differentiate between a critical incident and an accident. (2)
2.5 In the electrical workshop, you saw one of your classmates removing a safety
guard on a machine. According to the Occupational Health and Safety Act,
1993 (Act 85 of 1993), this is an unsafe act. Motivate why it is an unsafe act. (2)
[10]
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QUESTION 3: RLC CIRCUITS
3.1 With reference to RLC circuits, state the correct terminology that describes the
following:
3.1.1 The frequency at which XL is equal to XC (1)
3.1.2 The ratio of the energy stored to the energy converted by an inductor
or capacitor (1)
3.2 FIGURE 3.2 below shows an RLC series circuit connected to an AC supply.
Answer the questions that follow.
VR = 202,16 V VL = 226,82 V VC = 140,18 V
R XL = 62,83 Ω C = 100 µF
IT = 3,61 A
50 Hz
FIGURE 3.2: RLC SERIES CIRCUIT
Given:
IT = 3,61 A
XL = 62,83 Ω
C = 100 μF
VR = 202,16 V
VL = 226,82 V
VC = 140,18 V
f = 50 Hz
Calculate the following:
3.2.1 Supply voltage (3)
3.2.2 Impedance (3)
3.2.3 Phase angle (3)
3.2.4 Capacitance value that will cause resonance (3)
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3.3 Redraw and complete the voltage phasor diagram of QUESTION 3.2 in
FIGURE 3.3 below in the ANSWER BOOK.
IT = 3,61 A
FIGURE 3.3: INCOMPLETE VOLTAGE PHASOR DIAGRAM (4)
3.4 FIGURE 3.4 below shows an RLC parallel circuit with its corresponding phasor
diagram. Answer the questions that follow.
IC = 0,2 A
IR = 0,5 A VT = 50 V
50 Hz R L C
IL = 0,9 A
FIGURE 3.4: RLC PARALLEL CIRCUIT AND PHASOR DIAGRAM
Given:
VT = 50 V
IR = 0,5 A
IL = 0,9 A
IC = 0,2 A
f = 50 Hz
Calculate the following:
3.4.1 Total current (3)
3.4.2 Capacitive reactance (3)
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3.5 State whether the circuit in FIGURE 3.4 on the previous page is more capacitive
or more inductive. Give a reason for the answer. (2)
3.6 Refer to FIGURE 3.4 on the previous page and explain how an increase in the
supply frequency will cause the circuit to resonate. (3)
3.7 FIGURE 3.7 below shows the frequency response curve of an RLC circuit, NOT
to scale. Answer the questions that follow.
Zmax
70,7%
5,4 7,3 9,2 f (kHz)
FIGURE 3.7: Q-FACTOR CHARACTERISTIC CURVE
3.7.1 State whether FIGURE 3.7 above represents the response curve for
a series or parallel RLC circuit and motivate the answer. (2)
3.7.2 Calculate the Q-factor of the circuit. (4)
[35]
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QUESTION 4: SEMICONDUCTOR DEVICES
4.1 Refer to FIGURE 4.1 below and answer the questions that follow.
VGS
Gate
B A
Drain
VDS ID
FIGURE 4.1
4.1.1 Identify FIGURE 4.1 above. (1)
4.1.2 Label A and B. (2)
4.1.3 Explain why the negative terminal of VGS is connected to the gate in
FIGURE 4.1 above. (1)
4.1.4 Explain how a decrease in VGS would affect the drain current (ID). (2)
4.2 Refer to FIGURE 4.2 below and complete the output characteristic of a JFET
on the ANSWER SHEET for QUESTION 4.2 and label it.
I D (mA) I D (mA)
-VGS
(V) -6 -5 -4 -3 -2 -1 0
Transfer Characteristic Output Characteristic
FIGURE 4.2: INCOMPLETE OUTPUT CHARACTERISTIC OF A JFET (4)
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4.3 FIGURE 4.3 below shows a cross-section of a semiconductor. Answer the
questions that follow.
Source
S Gate
G Drain
D
B
N
A
FIGURE 4.3: CROSS-SECTION OF A SEMICONDUCTOR
4.3.1 Identify the semiconductor. (1)
4.3.2 Label A and B. (2)
4.3.3 Explain why the gate terminal is electrically insulated. (2)
4.4 Explain, with reference to the construction, how the MOSFET differs from the
JFET. (2)
4.5 Refer to FIGURE 4.5 below and complete the circuit diagram of a fully labelled
UJT as a saw-tooth generator on the ANSWER SHEET for QUESTION 4.5.
+V
0V
FIGURE 4.5: INCOMPLETE CIRCUIT OF A UJT AS
A SAW-TOOTH GENERATOR (5)
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4.6 Draw a fully labelled symbol of a Darlington transistor. (2)
4.7 State why the Darlington transistor is mainly used in switching and
amplification applications. (1)
4.8 Refer to FIGURE 4.8 below and answer the questions that follow.
8-PIN DIL PACKAGE
index
Indexdot
dot
offset null 1 8 not connected
inverting input 2 77 +V
741
non-inverting input 3 6 output
-V 4 5 offset null
FIGURE 4.8: 741 OP AMP
4.8.1 State the purpose of the index dot on the 741 IC in FIGURE 4.8
above. (1)
4.8.2 Describe the effect the op amp will have on a sine wave applied to
pin 2 in FIGURE 4.8 above. (2)
4.8.3 Explain why a 741 op amp requires a dual-rail power supply. (2)
4.9 Name the 741 op amp circuit that uses 100% feedback. (1)
4.10 The internal circuit of the 741 op amp consists of three stages, namely input
stage, intermediate stage and output stage. Explain the function of the
intermediate stage. (2)
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4.11 Refer to FIGURE 4.11 below and complete the circuit diagram of a 741 op amp
used as an inverting amplifier on the ANSWER SHEET for QUESTION 4.11.
+VCC
-
VIN +
V OUT
-VCC
FIGURE 4.11 (3)
4.12 FIGURE 4.12 below shows the internal layout of a 555 IC. Answer the questions
that follow.
+VCC A B Control voltage
8 7 6 5
5k
-
C1
+ R Q T2
Flip-
5k flop Q
S
-
C2
+
5k
T1
1 2 3 4
Ground Trigger Output Reset
FIGURE 4.12: INTERNAL LAYOUT OF A 555 IC
4.12.1 Label A and B. (2)
4.12.2 Explain why the RS flip-flop in FIGURE 4.12 above is also known as
a memory cell. (2)
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4.12.3 Explain why pin 4 is normally connected to the positive supply
voltage during operation. (2)
4.12.4 Explain how unwanted noise from the supply can be eliminated
during the operation of the 555 IC. (2)
4.12.5 Name ONE operating mode of a 555 IC. (1)
[45]
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QUESTION 5: SWITCHING CIRCUITS
5.1 Refer to op amps as switching circuits and answer the questions that follow.
5.1.1 Name ONE op amp switching circuit that operates in open-loop
mode. (1)
5.1.2 With reference to the inputs of an op amp, explain the term reference
voltage. (2)
5.2 FIGURE 5.2 below shows a bistable multivibrator circuit with a 555 IC. Answer
the questions that follow.
+ VCC
R2 R1
10 kΩ 10 kΩ
R3
8
4 330 Ω
7 555 3
6
2
1 5
LED
Set Reset
C2
0,01 µF
FIGURE 5.2: BISTABLE MULTIVIBRATOR
5.2.1 Explain the purpose of resistors R1 and R2 with reference to pins 2 and 4
when the set and reset switches are open. (2)
5.2.2 Explain what would happen if resistors R1 and R2 are bypassed with pins
2 and 4 directly connected to the supply. (2)
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5.2.3 Refer to FIGURE 5.2.3 below and complete the output signal for the
circuit in FIGURE 5.2 on the previous page on the ANSWER SHEET for
QUESTION 5.2.3.
VCC Trigger input when
set is pressed
0V
VCC Trigger input when
reset is pressed
0V
VCC Output
0V
FIGURE 5.2.3: BISTABLE INPUT (4)
5.3 Refer to FIGURE 5.3 below and answer the questions that follow.
+ 9V
R2 R1
10 kΩ 58 kΩ
8 4
7
Output
6 555 3
2 R3
5 1
470 Ω
Trigger
input C1 C2
47 µF 0, 01 µF LED
FIGURE 5.3: MONOSTABLE MULTIVIBRATOR
5.3.1 Name TWO practical applications of a monostable multivibrator
circuit. (2)
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5.3.2 Refer to FIGURE 5.3.2 below and draw on the ANSWER SHEET
for QUESTION 5.3.2, the waveforms for the voltage across
capacitor C1 (VC1) and the correlating output when the circuit in
FIGURE 5.3 on the previous page is set to have a time delay of 3
seconds once the trigger input is activated.
Trigger input
⅓ VCC
0V 1 2 3 4 5 t (s)
⅔VCC
VC1
t
High
Output
Low
t
FIGURE 5.3.2 (5)
5.3.3 Determine the threshold voltage value at which capacitor C1 will start
discharging. (2)
5.3.4 Refer to FIGURE 5.3.4 below and complete the equivalent
741 op amp monostable multivibrator circuit diagram on the
ANSWER SHEET for QUESTION 5.3.4.
+VCC
Input
Output
-VCC
-VREF
FIGURE 5.3.4: INCOMPLETE 741 MONOSTABLE
MULTIVIBRATOR (5)
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5.4 Refer to FIGURE 5.4 below and answer the questions that follow.
+15 V
VIN
VOUT
t
-15 V R1
9 kΩ
R2
1 kΩ
FIGURE 5.4: INVERTING SCHMITT TRIGGER
5.4.1 Name the type of feedback used in this circuit. (1)
5.4.2 Explain the term trigger voltage with reference to the circuit. (2)
5.4.3 Determine the approximate values of the upper AND lower trigger
voltages. (2)
5.4.4 Draw the output signal for the circuit in FIGURE 5.4 above on the
ANSWER SHEET for QUESTION 5.4.4. (4)
5.5 FIGURE 5.5 below shows a summing operational amplifier with RF set to
100 kΩ. ALL signals on the input are pure sine waves. Answer the questions
that follow.
C1 R1 10 kΩ RF 100 kΩ
V1
C2 R2 10 kΩ +12 V
-
V2 C3 R3 10 kΩ
+
VOUT
-12 V
V3
FIGURE 5.5: SUMMING AMPLIFIER
Given:
R1, R2, R3 = 10 kΩ
RF = 100 kΩ (variable)
V1, V2, V3 = 0,4 V
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5.5.1 Explain ONE characteristic that makes this type of circuit suitable for
use in audio mixing applications. (2)
5.5.2 Calculate the output voltage of the circuit if RF is set to 100 kΩ. (3)
5.5.3 Calculate the voltage gain of the amplifier. (3)
5.5.4 When V2 is increased to 0,6 V, the calculated output changes to
-14 V. Answer the following questions:
(a) Describe how the shape of the output signal will change when
V2 is increased to 0,6 V. (2)
(b) Explain why the output signal was affected in
QUESTION 5.5.4(a). (1)
(c) State how the change in signal shape can be fixed without
decreasing the value of any of the inputs. (1)
5.6 Refer to FIGURE 5.6 and answer the questions that follow.
RF
CIN +V
VIN
-
+V VOUT
Input
+
t -V
-V
FIGURE 5.6: OP-AMP DIFFERENTIATOR
5.6.1 Determine the voltage at the inverting input terminal of the op amp
before the input signal is fed into the circuit. Motivate your answer. (2)
5.6.2 Explain the relationship between the input and output voltage of the
circuit in FIGURE 5.6 above. (2)
[50]
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QUESTION 6: AMPLIFIERS
6.1 Briefly describe the purpose of an amplifier. (2)
6.2 Refer to FIGURE 6.2 below and answer the questions that follow.
IC(mA) IC(mA) IC(mA)
Saturation Saturation Saturation
Q2
Q3
Q1
VCE VCE VCE
(A) (B) (C)
FIGURE 6.2: DC LOAD LINES
6.2.1 State the class of amplification represented by FIGURE 6.2(A)
above. (1)
6.2.2 Explain why the positive half-cycle is distorted in FIGURE 6.2(B)
above. (2)
6.2.3 Identify the class of amplification at FIGURE 6.2(C) above. Motivate
your answer. (3)
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6.3 Refer to FIGURE 6.3 below and answer the questions that follow.
+VCC
R 1 = 10 k RC = 1 k
C 2 = 10 µF
C 1 = 10 µF
Q1
AC VOUT
R =5k
2
Supply
RE = 2 k
C E = 100 µF
0V
FIGURE 6.3: RESISTOR CAPACITOR-COUPLED AMPLIFIER
6.3.1 State how the reactances of the coupling (C1 and C2) and decoupling
capacitor (CE) will be affected at lower frequencies in FIGURE 6.3
above. (1)
6.3.2 Explain the function of R1 and R2 in FIGURE 6.3 above. (2)
6.3.3 Calculate the circuit's gain in decibels if the circuit produces 3 W of
sound when the input power is 6 W. (3)
6.3.4 Explain why R1 and C1 are referred to as a low-frequency filter. (3)
6.3.5 Draw the output waveform of the emitter amplifier on the ANSWER
SHEET for QUESTION 6.3.5. (3)
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6.4 FIGURE 6.4 below shows an amplifier circuit diagram. Answer the questions
that follow.
R1 Transformer R3 Speaker
T1
Transformer
T2
Q1 Q2
C2 C3
R2 RE1 C1 R4 RE2
0V
FIGURE 6.4: TWO-STAGE TRANSFORMER-COUPLED AMPLIFIER
6.4.1 State the function of transistor Q1. (1)
6.4.2 State TWO applications of the circuit in FIGURE 6.4 above. (2)
6.4.3 Describe the advantage of using a transformer-coupled amplifier
over a resistance-coupled amplifier. (2)
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6.5 Refer to FIGURE 6.5 below and answer the questions that follow.
+VCC
T2
R1 C1 C2 Output
T1
Q1
Input
R2 C3 R3 CE
0V
FIGURE 6.5: RADIO-FREQUENCY (RF) AMPLIFIER
6.5.1 Explain how the circuit in FIGURE 6.5 above is made more
frequency selective. (1)
6.5.2 Describe the primary function of the impedance matching network in
an RF amplifier. (2)
6.5.3 Describe how the circuit in FIGURE 6.5 above amplifies the input
signals. (3)
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6.6 FIGURE 6.6 below shows the circuit diagram of a Hartley oscillator. Answer the
questions that follow.
+ VCC
RF choke
C2 C4
R1
output
C3
Q1
L1
R2
R3
C5
C1
0V
L2
FIGURE 6.6: HARTLEY OSCILLATOR
6.6.1 Name the type of feedback the Hartley oscillator requires to oscillate. (1)
6.6.2 State the primary function of the tank circuit in the Hartley oscillator. (1)
6.6.3 Explain how varying the value of capacitor C1 in the tuned circuit
affects the frequency of operation. (2)
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6.7 Refer to FIGURE 6.7 below and answer the questions that follow.
+V +V
L= C=
300 mH 200 µF 0
Time
0V -V
(X) (Y)
FIGURE 6.7: TANK CIRCUIT DIAGRAM
6.7.1 Identify the waveform in FIGURE 6.7(Y) above. (1)
6.7.2 State how a reduction of the amplitude of the sinusoidal wave in
FIGURE 6.7(Y) above can be prevented. (1)
6.7.3 Explain the following terms with reference to FIGURE 6.7 above:
(a) Electrostatic charge of the capacitor (1)
(b) Electromagnetic charge of the inductor (1)
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6.8 Refer to FIGURE 6.8 below and answer the questions that follow.
+VCC
RB RC
C5
VOUT
C1 C2 C3
Q1
R1 R2 R3 R4 C4
0V
FIGURE 6.8: RC PHASE-SHIFT OSCILLATOR
6.8.1 Explain the purpose of variable resistor RC. (2)
6.8.2 State the function of R4 and C4. (2)
6.9 Differentiate between oscillators and amplifiers with reference to the feedback
used. (2)
[45]
TOTAL: 200
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FORMULA SHEET
RLC CIRCUITS SEMICONDUCTOR DEVICES
P = V I Cos θ VOUT R RF
XL = 2πfL Gain A V = =− F OR AV = 1+
VIN R IN R IN
1 RF
XC = VOUT =VIN × �- �
2π fC RIN
fr =
1 OR fr = f2 + f1 RF
2π LC 2 VOUT = VIN �1+ �
fr
RIN
BW = OR BW = f2 − f1
Q SWITCHING CIRCUITS
Series R R R
VOUT = − V1 F + V2 F + ...VN F
VR = I R R1 R2 RN
VL = I XL VOUT VOUT
Gain A V = =
VC = I X C VIN (V1 + V2 + ...VN )
VOUT = − ( V1 + V2 + ...VN )
R2
V
=FB VSAT ×
VT
R1 +R2
IT = OR IT = IR = IC = IL
Z
R2
V=
TRIG VOUT ×
R1 +R2
AMPLIFIERS
V
Z = R 2 + (X L − X C )
2
IC = C VCC = VCE + ICRC
RC
VR + (VL − VC ) OR
2 2
VT = VT = I Z VB = VBE + VRE
R OR Cos θ = VR OR Tan θ = VL - VC AV =
VOUT
Cos θ =
Z VT VR VIN
XL X C VL VC 1 L I
Q= = = = = A I = OUT
R R VT VT R C IIN
Parallel POUT
AP = OR AP=A V× A I
VT = VR = VL = VC PIN
VT
IR = βT = β1 x β2 OR A VT = A V1 × A V2 × A V3 × ...A Vn
R
PIN = I2 × Z IN AND POUT = I2 × Z OUT
VT
IC = R1 R2
XC =V1 × VCC =V2 × VCC
R1 +R2 R1 +R2
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VT Oscillation frequency
IL = 1 1
XL fo = OF fo =
2 × π LCT 2 × π 6 RC
2
IT =�IR + (IC - IL )2 1
fo =
2 × π LTC
GAIN IN DECIBELS
VT I
Z= A I = 20log10 OUT
IT IIN
I VOUT
Cos θ = R A V = 20log10 OR A V = 20log 10 A VT
IT VIN
R R POUT P2
Q= = A P = 10log10 OR A P = 10log10
XL X C PIN P1
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Electrical Technology: Electronics DBE/November 2025
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CENTRE NUMBER:
EXAMINATION NUMBER:
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QUESTION 4: SEMICONDUCTOR DEVICES
4.2
I D (mA) I D (mA)
-VGS
(V) -6 -5 -4 -3 -2 -1 0
Transfer Characteristic Output Characteristic
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MOD
FIGURE 4.2 (4)
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4.5
+V
0V
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MOD
FIGURE 4.5 (5)
4.11
+VCC
-
VIN +
V OUT
-VCC
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FIGURE 4.11 (3)
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QUESTION 5: SWITCHING CIRCUITS
5.2.3
VCC Trigger input when
set is pressed
0V
VCC Trigger input when
reset is pressed
0V
VCC Output
0V
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FIGURE 5.2.3 (4)
5.3.2
Trigger input
⅓ VCC
0V 1 2 3 4 5 t (s)
⅔VCC
VC1
t
High
Output
Low
t
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FIGURE 5.3.2 (5)
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5.3.4
+12 V
Input 2 7
6
Output
3
4
-12 V
-VREF
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FIGURE 5.3.4 (5)
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5.4.4
VIN
Boonste
Upper
snellervlak
trigger level
0
t
Onderste
Lower
snellervlak
trigger level
+V
VVOUT
UIT
0
t
-V
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FIGURE 5.4.4 (4)
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QUESTION 6: AMPLIFIERS
6.3.5
0V t
0V
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FIGURE 6.3.5 (3)
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