5.1 Name the type of multivibrator that: 5.1.1 Produces one pulse cycle of 'high' and 'low' when a trigger pulse is applied to its input. 5.1.2 Changes state when a trigger pulse is applied and remains in that state. 5.2 Refer to FIGURE 5.2 below and answer the questions that follow. 5.2.1 Name the function of resistors: (a) R1 (b) R3 5.2.2 State the state of the LED when trigger pin 2 is high. 5.2.3 Explain what happens in the circuit when the set switch is pressed. 5.2.4 Explain the purpose of connecting pin 6 to ground. 5.3 FIGURE 5.3 below shows an op amp as a comparator. The resistance of the LDR increases as the level of light falls. 5.3.1 State the purpose of R2. 5.3.2 Explain how an increase in the level of light affects the voltage on the non-inverting input. 5.3.3 Explain the operation of the circuit with reference to the voltages on the input terminals and the output voltage. 5.3.4 Predict the state of LED1 and LED2 when the voltage on the non-inverting terminal is higher than the voltage on the inverting terminal. 5.3.5 Draw out on the ANSWER SHEET for QUESTION 5.3.5. 5.4 Identify the type of Schmitt trigger circuit. 5.4.2 Determine the value of the output voltage when the voltage on the non-inverting input is -1 V. 5.4.3 State whether this circuit uses positive or negative feedback. 5.4.4 Explain the operation of the circuit with reference to the input and trigger voltage levels. 5.4.5 Predict how an increase in R1 will affect the trigger voltage levels. 5.4.6 Draw the output signal on the ANSWER SHEET for QUESTION 5.4.6. 5.5 Refer to FIGURE 5.5 below and answer the questions that follow. 5.5.1 The variable resistor Rf serves a dual purpose. Name both purposes. 5.5.2 Calculate the output voltage when the value of Rf is set to 78,26 kΩ. 5.5.3 Explain how an increase in the value of Rf affects the gain of the amplifier. 5.5.4 Describe why it is not recommended to increase the value of Rf beyond 78,26 kΩ. 5.5.5 Explain how this limitation can be overcome without changing the value of any of the resistors. 5.6 Refer to FIGURE 5.6 below and answer the questions that follow. 5.6.1 Draw the output when the value of C is changed to 1 µF on the ANSWER SHEET for QUESTION 5.6.1. 5.6.2 Draw the output when the value of C is changed to 100 µF on the ANSWER SHEET for QUESTION 5.6.2.

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5.1 Name the type of multivibrator that: 5.1.1 Produces one pulse cycle of 'high' and 'low' when a trigger pulse is applied to its input - NSC Electrical Technology Electronics - Question 5 - 2022 - Paper 1

Question 5

5.1-Name-the-type-of-multivibrator-that:-5.1.1-Produces-one-pulse-cycle-of-'high'-and-'low'-when-a-trigger-pulse-is-applied-to-its-input-NSC Electrical Technology Electronics-Question 5-2022-Paper 1.png

5.1 Name the type of multivibrator that: 5.1.1 Produces one pulse cycle of 'high' and 'low' when a trigger pulse is applied to its input. 5.1.2 Changes state when a ... show full transcript

Worked Solution & Example Answer:5.1 Name the type of multivibrator that: 5.1.1 Produces one pulse cycle of 'high' and 'low' when a trigger pulse is applied to its input - NSC Electrical Technology Electronics - Question 5 - 2022 - Paper 1

Step 1

Name the type of multivibrator that: 5.1.1

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The type of multivibrator that produces one pulse cycle of 'high' and 'low' when a trigger pulse is applied to its input is a Monostable Multivibrator.

Step 2

Name the type of multivibrator that: 5.1.2

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The type of multivibrator that changes state when a trigger pulse is applied and remains in that state is a Bistable Multivibrator.

Step 3

Refer to FIGURE 5.2 below and answer the questions that follow. 5.2.1 Name the function of resistors: (a) R1

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The function of resistor R1 is to keep the voltage on pin 4 high, which ensures that the 555 timer is active and ready to receive trigger pulses.

Step 4

Refer to FIGURE 5.2 below and answer the questions that follow. 5.2.1 Name the function of resistors: (b) R3

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The function of resistor R3 is to limit the current flowing to the LED, protecting it from excessive current that could burn it out.

Step 5

Refer to FIGURE 5.2 below and answer the questions that follow. 5.2.2 State the state of the LED when trigger pin 2 is high.

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When trigger pin 2 is high, the state of the LED is OFF.

Step 6

Refer to FIGURE 5.2 below and answer the questions that follow. 5.2.3 Explain what happens in the circuit when the set switch is pressed.

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When the set switch is pressed, it pulls pin 2 'low' (0 V), causing the output to go 'high'. This activates the LED by providing sufficient voltage across it.

Step 7

Refer to FIGURE 5.2 below and answer the questions that follow. 5.2.4 Explain the purpose of connecting pin 6 to ground.

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Connecting pin 6 to ground ensures the 555 timer can reset properly by providing a reference point for the threshold voltage, allowing the circuit to function as intended.

Step 8

FIGURE 5.3 below shows an op amp as a comparator. The resistance of the LDR increases as the level of light falls. 5.3.1 State the purpose of R2.

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The purpose of resistor R2 is to set the reference voltage on the inverting input of the op-amp comparator.

Step 9

FIGURE 5.3 below shows an op amp as a comparator. The resistance of the LDR increases as the level of light falls. 5.3.2 Explain how an increase in the level of light affects the voltage on the non-inverting input.

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As the level of light increases, the resistance of the LDR decreases, which increases the voltage on the non-inverting input of the op-amp.

Step 10

FIGURE 5.3 below shows an op amp as a comparator. The resistance of the LDR increases as the level of light falls. 5.3.3 Explain the operation of the circuit with reference to the voltages on the input terminals and the output voltage.

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The op-amp compares the voltages on its two input terminals. If the voltage on the non-inverting input is higher than that on the inverting input, the output drives to the positive saturation level. Conversely, if the inverting input is higher, the output goes to the negative saturation level.

Step 11

FIGURE 5.3 below shows an op amp as a comparator. The resistance of the LDR increases as the level of light falls. 5.3.4 Predict the state of LED1 and LED2 when the voltage on the non-inverting terminal is higher than the voltage on the inverting terminal.

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When the voltage on the non-inverting terminal is higher, LED1 will be ON (illuminated), while LED2 will be OFF.

Step 12

Identify the type of Schmitt trigger circuit. 5.4.1

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The type of Schmitt trigger circuit is an Inverting Schmitt Trigger.

Step 13

Determine the value of the output voltage when the voltage on the non-inverting input is -1 V. 5.4.2

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When the voltage on the non-inverting input is -1 V, the output voltage will be -10 V.

Step 14

State whether this circuit uses positive or negative feedback. 5.4.3

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This circuit uses positive feedback to create hysteresis, which helps in stabilizing the output.

Step 15

Explain the operation of the circuit with reference to the input and trigger voltage levels. 5.4.4

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The circuit operates by comparing the input voltage to two trigger voltage levels, the upper and lower thresholds. When the input exceeds the upper threshold, the output goes high, and when it falls below the lower threshold, the output goes low, creating a stable ON/OFF state.

Step 16

Predict how an increase in R1 will affect the trigger voltage levels. 5.4.5

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An increase in R1 will cause the trigger voltage levels to increase, shifting the points at which the output changes state.

Step 17

Refer to FIGURE 5.5 below and answer the questions that follow. 5.5.1 The variable resistor Rf serves a dual purpose. Name both purposes.

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The variable resistor Rf serves to control the gain of the amplifier and also allows for adjustable feedback in the circuit.

Step 18

Refer to FIGURE 5.5 below and answer the questions that follow. 5.5.2 Calculate the output voltage when the value of Rf is set to 78,26 kΩ.

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The output voltage can be calculated using the voltage divider formula:

$V_{out} = \frac{V_{in} R_f}{R_f + R_{2} + R_{3}}$ Given the values, we find: $V_{out} = \frac{(0.4)(78,260) + (0.5)(78,260) + (0.25)(78,260)}{100,000} = 9 V$

Step 19

Refer to FIGURE 5.5 below and answer the questions that follow. 5.5.3 Explain how an increase in the value of Rf affects the gain of the amplifier.

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An increase in the value of Rf will increase the gain of the amplifier, making it more sensitive to input signals. However, this may also lead to distortion if the output exceeds the supply limits.

Step 20

Refer to FIGURE 5.5 below and answer the questions that follow. 5.5.4 Describe why it is not recommended to increase the value of Rf beyond 78,26 kΩ.

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Increasing Rf beyond 78,26 kΩ is not recommended because it could push the amplifier into saturation and cause clipping of the output signal, leading to a loss of signal integrity.

Step 21

Refer to FIGURE 5.5 below and answer the questions that follow. 5.5.5 Explain how this limitation can be overcome without changing the value of any of the resistors.

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This limitation can be overcome by adjusting the supply voltage to the op-amp so that it can handle larger outputs without clipping, or by using feedback to stabilize the output.

Step 22

Refer to FIGURE 5.6 below and answer the questions that follow. 5.6.1 Draw the output when the value of C is changed to 1 µF on the ANSWER SHEET for QUESTION 5.6.1.

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The output waveform will represent the charging behavior of the capacitor, showing a more gradual rise and fall time as compared to the original value.

Step 23

Refer to FIGURE 5.6 below and answer the questions that follow. 5.6.2 Draw the output when the value of C is changed to 100 µF on the ANSWER SHEET for QUESTION 5.6.2.

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The output waveform will be even more gradual in charging and discharging, indicating a slower response time due to the larger capacitance.

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