Complete Electronics Self-Teaching Guide with Projects

Self-Test

These questions test your understanding of the concepts and equations presented in this chapter. Use a separate sheet of paper for your diagrams or calculations. Compare your answers with the answers provided following the test.

1. What are the three sections necessary in an oscillator?_____

2. What is the difference between positive and negative feedback?_____

3. What type of feedback is required in an oscillator?_____

4. What is the formula for the frequency of an oscillator?_____

5. Draw the circuit for a Colpitts oscillator.

6. Draw the circuit for a Hartley oscillator.

7. Draw the circuit for an Armstrong oscillator.

8. Problems 27–30 give a design procedure for oscillators. How well do the circuits in problem 35 fulfill the criteria for that procedure? In other words, check the values of V_f, A_V (for a common emitter amplifier), C₁/C₂ ratio, R_C/Z ratio, and the frequency.

A. _____

B. _____

C. _____

D. _____

9. For the circuit shown in Figure 9.38, calculate the values of C₁, C₂, C_C, and C_B for an oscillator with an output frequency of 10 kHz using a 100 mH coil.

Answers to Self-Test

If your answers do not agree with those provided here, review the problems indicated in parentheses before you go on to Chapter 10.

1.	An amplifier, feedback, and a resonant load.	(problem 1)
2.	Positive feedback is “in phase” with the input, and negative feedback is “out of phase” with the input.	(problems 2–3)
3.	Positive feedback.	(problem 3)
4.	(problem 11) ...