1. Electronics Technology Fundamentals Chapter 19 Bipolar Junction Transistor Operation and Biasing

2. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 2 19.1 Introduction to Bipolar Junction Transistors – P1 Transistor – a three-terminal device whose output current, voltage, and/or power are controlled by its input Transistor Williamson Lab

3. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 3 19.1 Introduction to Bipolar Junction Transistors – P2 Transistor Currents – under normal circumstances, I C and I E vary directly with the value of I B

4. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 4 19.1 Introduction to Bipolar Junction Transistors – P3 Transistor Currents (Continued) Normally, I C is some multiple of I B Forward Current Gain – the factor by which current increases from base to the collector, represented by the Greek letter beta (β)

5. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 5 19.1 Introduction to Bipolar Junction Transistors – P4Bipolar Junction Transistors Transistor Voltages HyperPhysics

6. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 6 19.2 Transistor Construction and Operation – P1 Two pn Junctions Make Up Transistor Base-Emitter Junction Collector-Base Junction

7. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 7 19.2 Transistor Construction and Operation – P2 Transistor Junctions – normally operated in one of three biasing combinations Base-Emitter Junction Collector-Base Junction Operating Region Reverse biased Forward biased Reverse biased Forward biased Cutoff Active Saturation

8. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 8 19.2 Transistor Construction and Operation – P3 No Bias and Cutoff Biasing sources reverse bias both junctions causing wide depletion layers Only a small amount of reverse current flows

9. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 9 19.2 Transistor Construction and Operation – P4 Saturation Opposite of cutoff Further increases in I B do not cause an increase in I C

10. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 10 19.2 Transistor Construction and Operation – P5 Active Operation – the base-emitter junction is forward biased and the collector-base junction is reverse biased

11. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 11 19.2 Transistor Construction and Operation – P6

12. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 12 19.3 Transistor Currents – P1 The Relationship Among I E, I C, and I B Kirchhoff’s Current Law – the current leaving a component must equal the current entering a component Since I B is much less than I C :

13. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 13 19.3 Transistor Currents – P2 DC Beta Ratio of the dc collector current to dc base current Typical Values: 50 to 300 Normally listed as dc current gain (h FE )

14. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 14 19.3 Transistor Currents – P3 DC Alpha – ratio of collector current to emitter current

15. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 15 19.3 Transistor Currents – P4 Collector Characteristic Curves – the relationship between I C and V CE at a specified value of I B

16. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 16 19.3 Transistor Currents – P5 Collector Characteristic Curves (Continued) – most amplifiers make use of the active region of operation (between V K and V BR )

17. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 17 19.3 Transistor Currents – P6 Collector Characteristic Curves (Continued) – Kirchhoff’s voltage law can be used to solve for V CE :

18. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 18 19.3 Transistor Currents – P7 Transistor Breakdown Occurs if V CE exceeds the breakdown rating of the transistor I C increases dramatically until the transistor is destroyed by excessive heat

19. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 19 19.4 Introduction to Transistor Biasing – P1 DC Biasing – used to set the initial values of I B, I C, and V CE for ac operation of the transistor DC Biasing

20. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 20 19.4 Introduction to Transistor Biasing – P2 The DC Load Line – a graph that represents every possible combination of I C and V CE

21. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 21 19.4 Introduction to Transistor Biasing – P3 The Q-Point The combination of I C and V CE on the dc load line where a transistor has no input signal Quiescent – at rest For linear operation, it is desirable to have the Q- point centered on the load line:

22. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 22 19.4 Introduction to Transistor Biasing – P4 The Q-Point (Continued) – an amplifier with a centered Q-point is said to be mid-point biased

23. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 23 19.5 Base Bias – P1 Base Bias (or Fixed Bias) – the simplest type of transistor biasing Base Bias

24. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 24 19.5 Base Bias – P2 Q-Point Shift – describes a condition where a change in transistor dc current gain (h FE ) causes a change in the Q-point values of I C and V CE

25. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 25 19.5 Base Bias – P3

26. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 26 19.6 Voltage-Divider Bias – P1 Voltage-Divider Bias – the most commonly used transistor bias circuit (also known as universal bias) Voltage-Divider Bias

27. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 27 19.6 Voltage-Divider Bias – P2 The following equation assumes that the loading effect of the transistor on the voltage divider is negligible The loading effect can be significant in some cases

28. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 28 19.6 Voltage-Divider Bias – P3 Transistor Loading – When I 2 < 10I B, ignoring the loading effect of the transistor does introduce significant errors Base Input Resistance – Just as current increases by a factor of h FE from the base to emitter, R E is effectively increased by the same factor.

29. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 29 19.6 Voltage-Divider Bias – P4

30. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 30 19.6 Voltage-Divider Bias – P5 Alternate (and more exact) approach to solving for I CQ and V CEQ

31. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 31 19.6 Voltage-Divider Bias – P6 Saturation and Cutoff Saturation, V CE = 0 V Cutoff

32. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 32 19.6 Voltage-Divider Bias – P7 Bias Stability The voltage-divider bias is a beta-independent circuit Values of I CQ and V CEQ are relatively stable against changes in beta (h FE )

33. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 33 19.6 Voltage-Divider Bias – P8 Bias Stability (Continued) I CQ = 1.46 mA for h FE = 50 I CQ = 1.56 mA for h FE = 100 Circuit experiences only a 6.8% increase in I CQ when h FE doubles in value

34. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 34 19.6 Voltage-Divider Bias – P9

35. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 35 19.7 Other Transistor Biasing Circuits – P1 Emitter-Bias – consists of several resistors and a dual-polarity power supply Emitter-Bias

36. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 36 19.7 Other Transistor Biasing Circuits – P2 Emitter-Bias (Continued) Saturation Cutoff

37. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 37 19.7 Other Transistor Biasing Circuits – P3

38. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 38 19.7 Other Transistor Biasing Circuits – P4 Collector-Feedback Bias Obtains Q-point stability as a result of the base resistor connection to the collector (feedback) Feedback – used to describe a circuit that “feeds” a portion of the output voltage or current back to the input

39. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 39 19.7 Other Transistor Biasing Circuits – P5 Collector-Feedback Bias (Continued) Insert Figure 19.31

40. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 40 19.7 Other Transistor Biasing Circuits – P6 Collector-Feedback Bias (Continued) Q-Point Stability – based on the fact that I B and beta are inversely related

41. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 41 19.7 Other Transistor Biasing Circuits – P7 Emitter-Feedback Bias – same basic operation as the collector-feedback bias, except the emitter circuit affects the value of I B Insert Figure 19.33

42. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 42 19.7 Other Transistor Biasing Circuits – P8

43. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 43 19.8 Related Topics – P1 Transistor Specification Sheets Maximum Ratings Breakdown Voltage Ratings Insert Figure 19.37

44. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 44 19.8 Related Topics – P2 Transistor Specification Sheets (Continued) Maximum Ratings (Continued) Current – maximum allowable continuous value of I C - must be derated as temperature increases Power Dissipation (P D ) – must be derated as temperature increases Off Characteristics – describes operation in cutoff Collector Cutoff Current (I CEX ) – the maximum value of I C when the device is in cutoff Base Cutoff Current (I BL ) – the maximum base current present when the device is in cutoff

45. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 45 19.8 Related Topics – P3 Transistor Specification Sheets (Continued) On Characteristics – describes the dc operating characteristics for both the active and saturation regions of operation dc Current Gain (h FE ) – the value of dc beta (β dc ) Collector-Emitter Saturation Voltage (V CE(sat) ) – the value of V CE when the transistor is operated in saturation Base-Emitter Saturation Voltage (V BE(sat) ) – the value of V BE when the transistor is operated in saturation

46. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 46 19.8 Related Topics – P4 Transistor Testing

47. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 47 19.8 Related Topics – P5 Transistor Testing (Continued)

48. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 48 19.8 Related Topics – P6 PNP Versus NPN Transistors

49. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 49 19.8 Related Topics – P7 Discrete Transistors Small-signal transistor (Example: 2N3904) – general, low power applications High-Voltage Transistors – used in circuits with high supply voltages. For example: television CRT control circuits High-Current Transistors – used in circuits with high current demands. For example: current regulator circuits High-Power Transistors – used in high-power circuits. For example: dc voltage regulators and stereo amplifier circuits

50. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 50 19.8 Related Topics – P8 Darlington Transistors Darlington Pair – a two- transistor configuration designed for high current gain Most often produced as a single component

51. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 51 19.8 Related Topics – P9 Darlington Transistors (Continued)

52. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 52 19.8 Related Topics – P10 Integrated Transistors Come in packages that house more than one transistor in integrated form Tend to have lower maximum power and current ratings than discrete transistors

53. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 53 19.8 Related Topics – P11 Surface-Mount Components (SMCs) Surface-Mount Much lighter and smaller than other types of components Mounted directly onto the surface of a PC board rather than into holes or fitted into IC sockets

54. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 54 19.8 Related Topics – P12 Surface-Mount Components (SMCs) (Continued)