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Refer to FIGURE 2.2 and answer the questions that follow - NSC Electrical Technology Digital - Question 2 - 2020 - Paper 1
Question 2
Refer to FIGURE 2.2 and answer the questions that follow. 2.2.1 Identify the multivibrator in FIGURE 2.2. 2.2.2 Describe the operation of the multivibrator in FIGU... show full transcript
Worked Solution & Example Answer:Refer to FIGURE 2.2 and answer the questions that follow - NSC Electrical Technology Digital - Question 2 - 2020 - Paper 1
Step 1
Step 2
2.2.2 Describe the operation of the multivibrator in FIGURE 2.2 from a point where the capacitor has just discharged.
Answer
At the moment the capacitor discharges, the voltage across it drops to 0 V. This causes the potential at the non-inverting terminal (A) of the operational amplifier (op-amp) to go below the reference voltage at the inverting terminal (B), resulting in the output of the op-amp switching to high (near +12 V). This high output charges the capacitor C1 through resistor R1. As C1 charges, its voltage gradually increases, and once it reaches a certain threshold (the reference voltage at point B), the output of the op-amp switches back to low (approximately 0 V). This cycle continues indefinitely, creating a square wave signal output.
Step 3
2.2.3 Explain how the frequency of the multivibrator in FIGURE 2.2 can be increased.
Answer
The frequency of the multivibrator can be increased by either decreasing the values of the resistors (R1 or R2) or by reducing the capacitance value of capacitor C1. A smaller capacitor or resistor allows the charging and discharging time of the capacitor to be shorter, resulting in a higher frequency output.