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3.1 State the difference between a monostable multivibrator and an astable multivibrator with reference to their output states - NSC Electrical Technology Digital - Question 3 - 2022 - Paper 1
Question 3
3.1 State the difference between a monostable multivibrator and an astable multivibrator with reference to their output states. 3.2 FIGURE 3.2 shows a bistable mult... show full transcript
Worked Solution & Example Answer:3.1 State the difference between a monostable multivibrator and an astable multivibrator with reference to their output states - NSC Electrical Technology Digital - Question 3 - 2022 - Paper 1
Step 1
State the difference between a monostable multivibrator and an astable multivibrator with reference to their output states.
Answer
A monostable multivibrator has only one stable state, which means it transitions briefly to its unstable state upon receiving a trigger and then returns to the stable state. An astable multivibrator, on the other hand, does not have a stable state; it continuously toggles between its high and low states, generating a square wave output.
Step 2
Step 3
Determine the voltage at the non-inverting input (Vb) when capacitor C2 is fully charged to the saturation voltage of 9 V and no current flows through R3.
Answer
When capacitor C2 is fully charged to its saturation voltage of 9 V, the voltage at the non-inverting input (Vb) will be 0 V, as the charge does not allow current to flow through R3, thus keeping the inverting input at a reference voltage.
Step 4
Explain what happens to the output voltage the moment a positive input pulse is applied to the inverting input.
Answer
Upon application of a positive input pulse at the inverting input, the output voltage transitions from a positive saturation level (9 V) to negative saturation (-9 V). This is due to the comparator action within the circuit, responding to the changes in voltage levels at its inputs.
Step 5
Draw the output waveform on the ANSWER SHEET for question 3.3.4.
Answer
The output waveform should reflect the changes corresponding to the input pulse being applied to the inverting input. It will represent variations that correspond to high and low states based on the timing set by C2 and R3.
Step 6
Step 7
Step 8
Describe how an increase in the value of RF affects the operation of the circuit.
Answer
Increasing the value of RF will increase the timing constant of the circuit, as it will result in a slower charge and discharge rate for the capacitor, thereby altering the frequency of the output signal and possibly reducing the overall frequency.
Step 9
Step 10
Explain the purpose of RF and R1 in the circuit.
Answer
RF and R1 are used to set the reference voltage at the non-inverting input of the operational amplifier in the Schmitt trigger configuration. These resistors help determine the trigger voltages that dictate when the output changes state.