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1. Tuned Circuits .......................................................................................................... 1-1

Q-1. What is the relationship between frequency and the values of (a) XL, (b)XC, and (c) R?A-1.a. XL varies directly with frequency.

XL = 2fLb. XC varies inversely with frequency.

c. Frequency has no affect on resistance.

Q-2. In an a.c. circuit that contains both an inductor and a capacitor, whatterm is used for the difference between the individual reactances?

A-2. Resultant reactance.

Q-3. State the formula for resonant frequency.A-3.

Q-4. If the inductor and capacitor values are increased, what happens to theresonant frequency?

A-4. Decreases.

Q-5. In an "ideal" resonant circuit, what is the relationship betweenimpedance and current?

A-5. Impedance low Current high.

Q-6. In a series-RLC circuit, what is the condition of the circuit if there is highimpedance, low current, and low reactance voltages?

A-6. Nonresonant (circuit is either above or below resonance).

Q-7. When the capacitor is completely discharged, where is the energy of thetank circuit stored?

A-7. Inductor magnetic field.

Q-8. When the magnetic field of the inductor is completely collapsed, whereis the energy of the tank circuit stored?

A-8. Capacitor.

Q-9. What is the term for the number of times per second that tank circuitenergy is either stored in the inductor or capacitor?

A-9. Natural frequency or resonant frequency (f r).

Q-10. In a parallel-resonant circuit, what is the relationship betweenimpedance and current?

A-10. Maximum impedance, minimum current.

Q-11. When is line current minimum in a parallel-LC circuit?

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A-11. At the resonant frequency.

Q-12. What is the relationship of the coil to the resistance of a circuit withhigh "Q"?

A-12.

Q-13. What is the band of frequencies called that is included between the twopoints at which current falls to 70 percent of its maximum value in a resonantcircuit?

A-13. Bandwidth of the circuit.

Q-14. What is the device called that will separate alternating current fromdirect current, or that will separate alternating current of one frequency fromother alternating currents of different frequencies?

A-14. A filter.

Q-15. What are the four general types of filters?A-15.a. Low-pass.b. High-passc. Bandpass.d. Band-reject.

Q-16. What is the filter called in which the low frequencies do not produce auseful voltage?

A-16. High-pass filter, low-frequency discriminator, or low-frequencyattenuator.

Q-17. What is the filter called that passes low frequencies but rejects orattenuates high frequencies?

A-17. Low-pass filter, high-frequency discriminator or high-frequencyattenuator.

Q-18. How does a capacitor and an inductor react to (a) low frequency and(b) high frequency?

A-18. At low-frequency, a capacitor acts as an open and an inductor acts as ashort. At high-frequency, a capacitor acts as a short and an inductor acts asan open.

Q-19. What term is used to describe the frequency at which the filter circuit

changes from the point of rejecting the unwanted frequencies to the point ofpassing the desired frequencies?A-19. Frequency cutoff (fco).

Q-20. What type filter is used to allow a narrow band of frequencies to passthrough a circuit and attenuate all other frequencies above or below thedesired band?

A-20. Bandpass.

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Q-21. What type filter is used to block the passage of current for a narrowband of frequencies, while allowing current to flow at all frequencies above orbelow this band?

A-21. Band-reject.

2. Oscillators................................................................................................................. 2-1

Q-1. What are the two classifications of wave generators according to theiroutput waveshapes?

A-1. Sinusoidal and nonsinusoidal.

Q-2. What are the three networks used for frequency-determining devices?A-2. RC, LC, and crystal.

Q-3. What is another name for nonsinusoidal oscillators?

A-3. Relaxation oscillators.

Q-4. What is a nonrotating device that produces alternating current?A-4. Oscillator.

Q-5. What are the three requirements necessary for oscillations to exist in acircuit?

A-5. Amplification, regenerative feedback, and frequency-determining device.

Q-6. What type of feedback aids an input signal?A-6. Regenerative or positive.

Q-7. What are the two methods used for feedback coupling?A-7. Inductive and capacitive.

Q-8. Which oscillator uses a tickler coil for feedback?A-8. Armstrong.

Q-9. Which oscillator uses a tapped inductor for feedback?A-9. Hartley.

Q-10. Which oscillator uses tapped capacitors for feedback?A-10. Colpitts.

Q-11. What are the three basic configurations of transistor oscillators?A-11. Common collector (CC), common emitter (CE), and common base (CB).

Q-12. What is the main difference between the Armstrong oscillator and theHartley oscillator?

A-12. Feedback coil. Armstrong uses a separate coil. Hartley uses a tappedcoil.

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Q-13. What is the difference between the series-fed and the shunt-fedHartley oscillator?

A-13. In the series-fed Hartley oscillator, dc flows through the tank circuit.

Q-14. What is the identifying feature of a Colpitts oscillator?A-14. Split capacitors.

Q-15. Which components provide the regenerative feedback signal in thephase-shift oscillator?A-15. Resistor-capacitor networks.

Q-16. Why is a high-gain transistor used in the phase-shift oscillator?A-16. Because of the losses encountered in the RC networks.

Q-17. Which RC network provides better frequency stability, three-section orfour-section?

A-17. Four-section.

Q-18. What is the impedance of a crystal at its resonant frequency when it isused in the parallel mode?

A-18. Maximum.

Q-19. What is the impedance of a crystal at its resonant frequency when it isused in the series mode?

A-19. Minimum.

Q-20. Oscillators that are turned on and off at a specific time are known aswhat type of oscillators?

A-20. Pulsed oscillators.

Q-21. What is the polarity of the first alternation of the tank circuit in anemitter-loaded npn pulsed oscillator?

A-21. Negative.

Q-22. What is the frequency that is twice the fundamental frequency?A-22. Second harmonic.

Q-23. What is the purpose of the buffer amplifier?A-23. Reduce interaction between oscillator and load.

3. Waveforms and Wave Generators............................................................................ 3-1

Q1. What type circuit is used to produce square or rectangular waves?A1. Multivibrator.

Q2. What type of multivibrator does not have a stable state?A2. Astable.

Q3. What type of multvibrator has one stable state?A3. Monostable.

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Q4. What type of multivibrator has two stable states?A4. Bistable.

Q5. In an astable multivibrator, which components determine the pulserepetition frequency?

A5. RC coupling networks.

Q6. What is another name for the monostable multivibrator?A6. One-shot.

Q7. In a bistable multivibrator, how many trigger pulses are needed toproduce one complete cycle in the output?A7. Two.

Q8. How many stable states are there for a flip-flop?A8. Two.

Q9. If a voltage (positive or negative) is measured on the "1" output of a flip-

flop, what state is it in?A9. SET state.

Q10. What component in a blocking oscillator controls pulse width?A10. Transformer.

Q11. For an RC circuit to produce a linear output across the capacitor, thevoltage across the capacitor may not exceed what percent of the appliedvoltage?

A11. Ten percent.

Q12. Increasing gate length in a sawtooth generator does what to linearity?

A12. Decreases linearity.

Q13. In a sawtooth generator, why is the transistor turned on for a longertime than the discharge time of the RC network?

A13. To allow the capacitor time to discharge.

Q14. What is added to a sawtooth generator to produce a trapezoidal wave?A14. A resistor.

4. Wave Shaping........................................................................................................... 4-1

Q1. Which portion of a sine-wave input is retained in the output of a series-

positive limiter?A1. Negative.

Q2. Which portion of a sine-wave input is retained in the output of a series-negative limiter?

A2. Positive.

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Q3. How can a series-positive limiter be modified to limit unwanted negativeportions of the input signal?A3. Biasing.

Q4. What component is in parallel with the output in a parallel limiter?A4. The diode.

Q5. What is the condition of the diode in a series limiter when an output isdeveloped? In a parallel limiter?

A5. Conducting, cutoff.

Q6. What is the relative length of the time constant for the diode-capacitorcombination in a damper (long or short)?

A6. Short time constant.

Q7. What is the relative length of the discharge time constant with respect tothe charge time constant of a damper (long or short)?

A7. Long time constant.

Q8. A positive damper clamps which extremity of the output signal to 0 volts?A8. Most negative.

Q9. To which polarity does a positive damper with positive bins clamp themost negative extremity of the output waveform (positive or negative)?

A9. Positive potential.

Q10. What type damper (with bias) clamps the most negative extremity ofthe output waveform to a negative potential?

A10. Positive clamper with negative bias.

Q11. A negative damper damps which extremity of the output waveshape to0 volts?

A11. Most positive.

Q12. A negative damper with negative bias clamps the most positiveextremity of the output wave shape to what polarity (positive or negative)?

A12. Negative potential.

Q13. What type of bias (positive or negative) is added to a negative damperfor the most positive extremity of the wave shape to be clamped above 0volts?

A13. Positive bias.

Q14. What would be the output of a negative clamper with a bias potential of 5 volts and an input voltage swing from +50 to 50 volts?A14. -5 volts.

Q15. What is the harmonic composition of a square wave?

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A15. It is composed of an infinite number of odd harmonics in phase with thefundamental.

Q16. What is the peaked wave composed of?A16. It is composed of odd harmonics some of which are out phase with thefundamental.

Q17. What is the fundamental difference between the phase relationship ofthe harmonics of the square wave as compared to the harmonics of a peakedwave?

A17. All the odd harmonics are in phase with the fundamental in the squarewave. This is not true of the odd harmonics in the peaked wave.

Q18. What are the requirements for an integration circuit?A18. The time constant is long and the output is taken across the capacitor inan RC circuit.

Q19. Can a pure sine wave be integrated? Why?

A19. A pure sine wave cannot be integrated; it contains no harmonics.

Q20. What characteristic of an RL circuit allows it to act as an integrator?A20. The ability of the inductor to oppose a change in current.

Q21. What is the numerical difference (in terms of the time constant)between a long and a short time constant circuit?

A21. The time-constant value of a long time constant-circuit is 10 times thevalue of the input pulse duration. The short time-constant circuit has a timeconstant of 1/10 of the pulse duration.

Q22. What would happen to the integrator output if the capacitor were made

extremely large (all other factors remaining the same)?A22. A more complete integration of the waveform would result from the longtime constant.

Q23. What is the difference between an RC and an RL differentiator in termsof where the output is developed?

A23. In an RC circuit the output is taken across the resistor. In the RL circuitthe output is taken across the inductor.

Q24. Name a common application of counting circuits.A24. Frequency counters or frequency dividers.

Q27. What is the difference between a positive counter and a step counter?A27. The load resistor in a positive counter is replaced by a capacitor in astep counter.