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# ND 2 past question on Electronics iii (EEC 224 )

ELECTRICAL ENGINEERING DEPARTMENT

SECOND SEMESTER EXAMINATION

CLASS:                               ND II

COURSE TITLE:                 ELECTRONICS II

COURSE CODE:                 EEC 224

TIME ALLOWED                    2 Hours

INSTRUCTION:                      (i) QUESTION THREE (3) IS COMPULSORY AND CARRIES 20 MARKS.

(ii)  ANSWER  ANY  THREE (3) QUESTIONS

QUESTION ONE

1. With the aid of diagram, derive from the basic principle the feedback equation for both Positive and Negative feedback in an amplifier.
2. State four (4) comparison between Positive and Negative feedback.
3. With a suitable diagram, explain the principle of operation of an Oscillator.

QUESTION TWO

1. Explain six (6) factors that affect the stability of an Oscillator and their various remedies.
2. List four 94) various types of Oscillator
3. State two (2) advantages and two (2) disadvantages of RC Phase Shift Oscillator

QUESTION THREE

1. An amplifier when first built has an open loop gain of 100, after a while due to ageing, it falls to 80.
2. Calculate the percentage reduction in gain.

If the same amplifier has 10% of the negative feedback applied:

1. Calculate the gain with feedback before and after ageing
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ELECTRICAL ENGINEERING DEPARTMENT

SECOND SEMESTER EXAMINATION

CLASS:                               ND II

COURSE TITLE:                 ELECTRONICS II

COURSE CODE:                 EEC 224

TIME ALLOWED                    2 Hours

INSTRUCTION:                      (i) QUESTION THREE (3) IS COMPULSORY AND CARRIES 20 MARKS.

(ii)  ANSWER  ANY  THREE (3) QUESTIONS

QUESTION ONE

1. A frequency determining circuit in an L-C sine-wave Oscillator consist of a high Q inductance L= 200µH in parallel with a capacitor of C=450Pf. Determine the frequency of Oscillation. A variable capacitor C1 is connected in parallel with the L-C circuit. Determine the frequency range of the Oscillator if this capacitor can be varied from 20Pf-150Pf.
2. What do you understand by Oscillator? And State four (4) necessary conditions for a circuit to Oscillate.
3. Define Positive and Negative feedback in amplifiers.
4. Mention four (4) advantages of Negative feedback.

QUESTION TWO

1. A tuned-collector Oscillator has a fixed inductance of 75µH and has to be tunable over the frequency band of 500KHz-1500KHz. Find the range of variable capacitor to be used.
2. Explain six (6) factors that affect the stability of an Oscillator and their various remedies.

QUESTION THREE

1. With the aid of diagram, derive from the basic principle the feedback equation for both Positive and Negative feedback in an amplifier.
2. An inverting amplifier has an open loop gain of 140 and a bandwidth of  10KHz. Calculate the gain and bandwidth resulting from the application of 4% negative feedback.
3. Mention four (4) various types of Oscillator.

ELECTRICAL ENGINEERING DEPARTMENT

SECOND SEMESTER EXAMINATION

CLASS:                               ND II

COURSE TITLE:                 ELECTRONICS II

COURSE CODE:                 EEC 224

TIME ALLOWED                    2 Hours

INSTRUCTION:                      (i) QUESTION THREE (3) IS COMPULSORY AND CARRIES 20 MARKS.

(ii)  ANSWER  ANY  THREE (3) QUESTIONS

QUESTION ONE

1. With the aid of suitable diagram, explain briefly the principle of operation of a Full-Wave bridge rectifier.
2. Explain in some details PID control and state its limitations.
3. State five (5) comparisons between Positive and Negative feedback.

QUESTION TWO

1. A tuned-collector Oscillator has a fixed inductance of 100µH and has to be tunable over the frequency band of 500KHz-1500KHz. Find the range of variable capacitor to be used.
2. Mention four (4) advantages of

QUESTION FIVE

1. Explain six (6) factors that affect the stability of an Oscillator and their vaeious remedies.
2. Explain briefly four (4) parameters of Operational Amplifier.
3. State five (5) uses of Multi-vibrators.

QUESTION SIX

1. Describe briefly the ideal operational amplifier (op-amp) and its characteristics.
2. Explain briefly the difference between Astable, Monostable and Bistable Multi-vibrators.
3. An amplifier with an open loop gain of 120 has negative feedback applied. When providing an output of 10v the amplifier introduce 20% of distortion and introduces 5Mv of noise. Calculate the improvement in distortion and noise when β=0.01
4. With the aid of a suitable diagram, describe the basic internal arrangement of operational amplifier (Op-amp).