Transistors

Q8. In the NPN transistor, what section is made very thin compared with the other two sections?

A8. The P or base section.

Q9. What percentage of current in an NPN transistor reaches the collector?

A9. 98 percent.

Q35. What does the number "2" (before the letter "N") indicate in the JAN marking scheme?

A35. The number of junctions in the device, which in this case indicates a transistor.

Q36. What is the greatest danger to a transistor?

A36. Heat.

Q37. What method for checking transistors is cumbersome when more than one transistor is bad in a circuit?

A37. The substitution method.

Q38. What safety precaution must be taken before replacing a transistor?

A38. The power must be removed from the circuit.

Q39. How is the collector lead identified on an oval-shaped transistor?

A39. By the wide space between the collector lead and the other two leads (emitter and base).

Q4. What was the name of the very first transistor?

A4. Point-contact.

Q40. What are two transistor tests that can be done with an ohmmeter?

A40. Gain and junction resistance.

Q41. When you are testing the gain of an audio-frequency transistor with an ohmmeter, what is indicated by a 10-to-1 resistance ratio?

A41. Normal gain.

Q42. When you are using an ohmmeter to test a transistor for leakage, what is indicated by a low, but not shorted, reverse resistance reading?

A42. A leaking transistor

Q5. What is one of the most important parts of any transistor manufacturing process?

A5. Quality control.

Q6. To properly bias an NPN transistor, what polarity voltage is applied to the collector, and what is its relationship to the base voltage?

A6. Positive, more positive.

Q7. Why is conduction through the forward-biased junction of an NPN transistor primarily in one direction, namely from the emitter to base?

A7. Because the N material on one side of the forward-biased junction is more heavily doped than the P-material.

Q1. What is the name given to the semiconductor device that has three or more elements?

A1. Transistor

Q10. What are the majority current carriers in a PNP transistor?

A10. Holes.

Q11. What is the relationship between the polarity of the voltage applied to the PNP transistor and that applied to the NPN transistor?

A11. The polarity of voltage applied to the PNP transistor is opposite of that applied to the NPN transistor

Q12. What is the letter designation for base current?

A12. IB.

Q13. Name the two current loops in a transistor.

A13. The base current loop and the collector current loop.

Q14. What is the name of the device that provides an increase in current, voltage, or power of a signal without appreciably altering the original signal?

A14. Amplifier.

Q15. Besides eliminating the emitter-base battery, what other advantages can different biasing methods offer?

A15. Compensation for slight variations in transistor characteristics and changes in transistor conduction because of temperature variations.

Q16. In the basic transistor amplifier discussed earlier, what is the relationship between the polarity of the input and output signals?

A16. The signals are opposite in polarity or 180 degrees out of phase with each other.

Q17. What is the primary difference between the NPN and PNP amplifiers?

A17. The polarity of the source voltage.

Q18. Which biasing method is the most unstable?

A18. Base current bias or fixed bias.

Q19. What type of bias is used where only moderate changes in ambient temperature are expected?

A19. Self-bias.

Q2. What electronic function made the transistor famous?

A2. Amplification.

Q20. When is degeneration tolerable in an amplifier?

A20. When it is necessary to prevent amplitude distortion.

Q21. What is the most widely used combination-bias system?

A21. The voltage-divider type.

Q22. What amplifier class of operation allows collector current to flow during the complete cycle of the input?

A22. Class A.

Q23. What is the name of the term used to describe the condition in a transistor when the emitter-base junction has zero bias or is reverse biased and there is no collector current?

A23. Cutoff.

Q24. What two primary items determine the class of operation of an amplifier?

A24. The amount of bias and the amplitude of the input signal.

Q25. What amplifier class of operation is the most inefficient but has the least distortion?

A25. Class A.

Q26. What are the three transistor configurations?

A26. Common emitter (CE), common base (CB), and common collector (CC).

Q27. Which transistor configuration provides a phase reversal between the input and output signals?

A27. Common emitter.

Q28. What is the input current in the common-emitter circuit?

A28. Base current (IB).

Q29. What is the current gain in a common-base circuit called?

A29. Alpha (α).

Q3. In which direction does the arrow point on an NPN transistor?

A3. Outward.

Q30. Which transistor configuration has a current gain of less than 1?

A30. Common base.

Q31. What is the output current in the common-collector circuit?

A31. IE.

Q32. Which transistor configuration has the highest input resistance?

A32. Common collector.

Q33. What is the formula for GAMMA (γ)?

A33. Y = IE/IB

Q34. List three items of information normally included in the general description section of a specification sheet for a transistor.

A34. The kind of transistor, the transistor's common applications, and mechanical data.