4.1 Name ONE mode of operation of the metal-oxide-semiconductor field-effect transistor (MOSFET). 4.2 Refer to FIGURE 4.2 below and answer the questions that follow. 4.2.1 Identify the semiconductor symbol in FIGURE 4.2. 4.2.2 Explain how the metal-oxide-semiconductor field-effect transistor (MOSFET) differs from the junction field-effect transistor (JFET) with reference to its construction. 4.3 Refer to FIGURE 4.3 below and answer the questions that follow. 4.3.1 Identify pulses B2. 4.3.2 Explain the term saturation region with reference to the operation of the UJT. 4.3.3 Describe how the UJT is driven into the CUT-OFF mode. 4.3.4 Draw the output voltage waveform across R2 on the ANSWER SHEET for QUESTION 4.3.4. 4.4 Refer to FIGURE 4.4 below and answer the questions that follow. 4.4.1 Identify the circuit diagram in FIGURE 4.4. 4.4.2 Describe how the transistors are biased and fully turned ON by referring to the required voltages. 4.4.3 State TWO advantages of the circuit in FIGURE 4.4. 4.4.4 Explain why the transistor in FIGURE 4.4 is preferred over a single transistor when used as a switch. 4.5 FIGURE 4.5 below shows an operational amplifier. Answer the questions that follow. 4.5.1 Identify the type of operational amplifier in FIGURE 4.5. 4.5.2 Draw the output voltage waveform on the ANSWER SHEET for QUESTION 4.5.2. 4.5.3 Explain why operational amplifiers are known as differential voltage amplifiers. 4.6 Refer to FIGURE 4.6 below and answer the questions that follow. 4.6.1 Explain the function of the RS flip-flop. 4.6.2 State the typical operating voltage range of the 555 IC. 4.6.3 Name TWO modes of operation for the 555 IC. 4.6.5 Explain the function of the threshold input on Pin 6 of 555 Timer IC. 4.7 Refer to FIGURE 4.7 below and explain why the output is zero volts. 4.8 Refer to FIGURE 4.8 below and answer the questions that follow. 4.8.1 Calculate the output voltage. 4.8.2 Explain the effect on the output when the value of the feedback resistor is equal to that of the input resistor.

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4.1 Name ONE mode of operation of the metal-oxide-semiconductor field-effect transistor (MOSFET) - NSC Electrical Technology Electronics - Question 4 - 2021 - Paper 1

Question 4

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4.1 Name ONE mode of operation of the metal-oxide-semiconductor field-effect transistor (MOSFET). 4.2 Refer to FIGURE 4.2 below and answer the questions that follow... show full transcript

Worked Solution & Example Answer:4.1 Name ONE mode of operation of the metal-oxide-semiconductor field-effect transistor (MOSFET) - NSC Electrical Technology Electronics - Question 4 - 2021 - Paper 1

Step 1

4.1 Name ONE mode of operation of the metal-oxide-semiconductor field-effect transistor (MOSFET).

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Answer

Enhancement Mode MOSFET.

Step 2

4.2.1 Identify the semiconductor symbol in FIGURE 4.2.

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Answer

The semiconductor symbol in FIGURE 4.2 is that of a MOSFET, specifically a P-channel enhancement mode.

Step 3

4.2.2 Explain how the metal-oxide-semiconductor field-effect transistor (MOSFET) differs from the junction field-effect transistor (JFET) with reference to its construction.

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The MOSFET has a metal-oxide layer that provides insulation between the gate electrode and the channel, while in a JFET, the gate and the channel are physically connected.

Step 4

4.3.1 Identify pulses B2.

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Pulses B2 are Sawtooth pulses.

Step 5

4.3.2 Explain the term saturation region with reference to the operation of the UJT.

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Answer

The saturation region occurs when the operating point has fallen beyond the valley point, and the emitter has been supplied with sufficient current.

Step 6

4.3.3 Describe how the UJT is driven into the CUT-OFF mode.

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The UJT is driven into the cut-off mode when the voltage across the capacitor falls to the UJT's emitter-base junction, consequently resetting the conditions.

Step 7

4.3.4 Draw the output voltage waveform across R2 on the ANSWER SHEET for QUESTION 4.3.4.

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A sketch of the output voltage waveform across R2 should reflect the behavior of the UJT circuit, showing the transition between cut-off and saturation.

Step 8

4.4.1 Identify the circuit diagram in FIGURE 4.4.

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The circuit diagram in FIGURE 4.4 is a Darlington transistor amplifier.

Step 9

4.4.2 Describe how the transistors are biased and fully turned ON by referring to the required voltages.

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To fully turn on the transistors, a supply voltage exceeding 1.4 V is connected to the base of the Darlington transistor, ensuring sufficient biasing of both the base-emitter and collector-emitter junctions.

Step 10

4.4.3 State TWO advantages of the circuit in FIGURE 4.4.

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It can supply high current gain.
It has improved input impedance, reducing load on the preceding stages.

Step 11

4.4.4 Explain why the transistor in FIGURE 4.4 is preferred over a single transistor when used as a switch.

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A Darlington transistor is preferred because it can energize and operate switching devices that demand higher current.

Step 12

4.5.1 Identify the type of operational amplifier in FIGURE 4.5.

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The operational amplifier in FIGURE 4.5 is a Non-Inverting Operational Amplifier.

Step 13

4.5.2 Draw the output voltage waveform on the ANSWER SHEET for QUESTION 4.5.2.

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The output waveform should show the amplified response with a phase shift of zero from the input signal.

Step 14

4.5.3 Explain why operational amplifiers are known as differential voltage amplifiers.

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Operational amplifiers amplify the difference in voltage between two input signals, which makes them effective as differential amplifiers.

Step 15

4.6.1 Explain the function of the RS flip-flop.

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The RS flip-flop stores the last received information until new information is provided by its two stable states.

Step 16

4.6.2 State the typical operating voltage range of the 555 IC.

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Answer

+5 V to (+15 V or +18 V).

Step 17

4.6.3 Name TWO modes of operation for the 555 IC.

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Astable Mode
Monostable Mode.

Step 18

4.6.5 Explain the function of the threshold input on Pin 6 of 555 Timer IC.

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The threshold input monitors the voltage at which a 555 IC will reset when the voltage exceeds $rac{1}{3} V_{CC}$ .

Step 19

4.7 Refer to FIGURE 4.7 below and explain why the output is zero volts.

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The output of the 741 Op-Amp is zero volts due to equal amplitudes at both inputs, causing cancellation.

Step 20

4.8.1 Calculate the output voltage.

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Given the values, the output voltage can be calculated using the formula: $V_{out} = V_{in} \left(1 + \frac{R_f}{R_n}\right)$ Substituting, we find: $V_{out} = 2.5 mV \left(1 + \frac{110}{2.2}\right) = 127.5 mV$ .

Step 21

4.8.2 Explain the effect on the output when the value of the feedback resistor is equal to that of the input resistor.

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Answer

When the feedback resistor is equal to the input resistor, the output voltage will be twice that of the input voltage.

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