__THE POLYTECHNIC, IBADAN__

__ELECTRICAL ENGINEERING DEPARTMENT__

__SECOND SEMESTER EXAMINATION__

__ 2012/2013 ACADEMIC SESSION__

**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__

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

**QUESTION TWO**

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

**QUESTION THREE**

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

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

- Calculate the gain with feedback before and after ageing
- WATCH VIDEO

__THE POLYTECHNIC, IBADAN__

__ELECTRICAL ENGINEERING DEPARTMENT__

__SECOND SEMESTER EXAMINATION__

__ 2011/2012 ACADEMIC SESSION__

**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__

- A frequency determining circuit in an L-C sine-wave Oscillator consist of a high Q inductance L= 200ÂµH 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.
- What do you understand by Oscillator? And State four (4) necessary conditions for a circuit to Oscillate.
- Define Positive and Negative feedback in amplifiers.
- Mention four (4) advantages of Negative feedback.

__QUESTION TWO__

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

__QUESTION THREE__

- With the aid of diagram, derive from the basic principle the feedback equation for both Positive and Negative feedback in an amplifier.
- 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.
- Mention four (4) various types of Oscillator.

__THE POLYTECHNIC, IBADAN__

__ELECTRICAL ENGINEERING DEPARTMENT__

__SECOND SEMESTER EXAMINATION__

__ 2014/2015 ACADEMIC SESSION__

**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__

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

__QUESTION TWO__

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

__QUESTION FIVE__

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

__QUESTION SIX__

- Describe briefly the ideal operational amplifier (op-amp) and its characteristics.
- Explain briefly the difference between Astable, Monostable and Bistable Multi-vibrators.
- 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 Î²=0.01
- With the aid of a suitable diagram, describe the basic internal arrangement of operational amplifier (Op-amp).

YOUTUBE: https://youtu.be/_aOjLFWuBLQ