Questions and Problems

Author: N.H. Crowhurst

1. What limits the dynamic range that an amplifier can handle?

2. What is the difference between the dynamic range of a single stage of amplification and that of a complete amplifier? How would you expect dynamic range to vary with (a) the total amplifier gain, (b) its frequency response?

3. Why does most noise in audio systems manifest itself as a hissing sound from the loudspeaker?

4. Why does a communications receiver use a very limited bandwidth, while a high-fidelity system should have a wide frequency response?

5. How can an input transformer help to increase dynamic range, and under what conditions will it do so?

6. What is the predominant cause of distortion in amplifiers (a) at low levels, (b) at higher levels?

7. What is a time base, and for what is it particularly useful in audio?

8. How does the time difference between input and output sine waves occur, due to the effects of coupling capacitors and how can this be shown on an oscilloscope?

9. What is capacitive reactance? How does reactance differ from resistance?

10. When the reactance in a circuit rises to a point equal to the resistance, the voltage does not drop to half its original value. Why? Explain the significance of the 3-db point.

11. Explain how circuit resistance values in the coupling between amplifying stages can affect frequency response, and show what are the important quantities for low- and high-frequency response, both for triode and pentode stages.

12. What is the essential difference between the uses of tubes for voltage amplification and for power amplification?

13. Why is resistance-capacitance coupling, so often used for voltage amplifiers, not economic for power stages?

14. Explain the advantages of a transformer for power-stage couping.

15. How does a pentode improve the possibilities of performance (a) of a voltage amplifier, (b) of a power-output stage?

16. What is the difference between a pentode and a beam power tube? Can either of these tubes be connected in such a way as to work as a triode?