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1. Elektronika AgusSetyo Budi, Dr. M.Sc Sesion #16 JurusanFisika FakultasMatematikadanIlmuPengetahuanAlam

2. Outline 28-1: Transistor Construction 28-2: Proper Transistor Biasing 28-3: Operating Regions 28-4: Transistor Ratings 28-5: Checking a Transistor with an Ohmmeter 28-6: Transistor Biasing © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 2 07/01/2011

3. Bipolar Junction Transistors 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 3

4. 28-1: Transistor Construction A transistor has three doped regions, as shown in Fig. 28-1 (next slide). Fig. 28-1 (a) shows an npn transistor, and a pnp is shown in (b). For both types, the base is a narrow region sandwiched between the larger collector and emitter regions. 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 4

6. The base region is very thin and lightly doped.

7. Most of the current carriers injected into the base pass on to the collector.

8. The collector region is moderately doped and is the largest of all three regions.Fig. 28-1 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 5

9. 28-2: Proper Transistor Biasing For a transistor to function properly as an amplifier, the emitter-base junction must be forward-biased and the collector-base junction must be reverse-biased. The common connection for the voltage sources are at the base lead of the transistor. The emitter-base supply voltage is designated VEE and the collector-base supply voltage is designated VCC. 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 6

11. Proper biasing for an npn transistor is shown in (a).

12. The EB junction is forward-biased by the emitter supply voltage, VEE.

13. VCC reverse-biases the CB junction.

14. Fig. 28-4 (b) illustrates currents in a transistor.Fig. 28-4 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 7

16. By varying IB, a transistor can be made to operate in any one of the following regions

17. Saturation

18. Breakdown

19. Cutoff

20. ActiveFig. 28-6: Common-emitter connection (a) circuit. (b) Graph of IC versus VCE for different base current values. 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 8

22. The base-emitter junction acts like a forward-biased diode with current, IB.

23. Usually, the second approximation of a diode is used.

24. If the transistor is silicon, assume that VBE equals 0.7 V.Fig. 28-7 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 9

25. 28-4: Transistor Ratings A transistor, like any other device, has limitations on its operations. These limitations are specified in the manufacturer’s data sheet. Maximum ratings are given for Collector-base voltage Collector-emitter voltage Emitter-base voltage Collector current Power dissipation 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 10

27. This is illustrated in Fig. 28-8 where the npn transistor is replaced by its diode equivalent circuit.Fig. 28-8 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 11

29. For a good p-n junction made of silicon, the ratio RR/RF should be equal to or greater than 1000:1.Fig. 28-9 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 12

31. For a good p-n junction made of silicon, the ratio RR/RF should be equal to or greater than 1000:1.

32. Although not shown, the resistance measured between the collector and emitter should read high or infinite for both connections of the meter leads.Fig. 28-10 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 13

33. 28-6: Transistor Biasing For a transistor to function properly as an amplifier, an external dc supply voltage must be applied to produce the desired collector current. Bias is defined as a control voltage or current. Transistors must be biased correctly to produce the desired circuit voltages and currents. The most common techniques used in biasing are Base Voltage-divider Emitter 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 14

35. VBB is the base supply voltage, which is used to forward-bias the base-emitter junction.

36. RB is used to provide the desired value of base current.

37. VCC is the collector supply voltage, which provides the reverse-bias voltage required for the collector-base junction.

38. The collector resistor, RC, provides the desired voltage in the collector circuit.Fig. 28-12 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 15

40. For every value of collector current, IC, the corresponding value of VCE can be found by examining the dc load line.

41. A sample dc load line is shown in Fig. 28-14.Fig. 28-14 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 16

42. 28-6: Transistor Biasing Fig. 28-15 illustrates a dc load line showing the end points IC (sat) and VCE (off), as well as the Q point values ICQ and VCEQ. Fig. 28-15 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 17

44. The advantage of voltage-divider bias lies in its stability.

45. An example of voltage-divider bias is shown in Fig. 28-18.Fig. 28-18 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 18

47. End points and Q points are

48. IC (sat) = 12.09 mA

49. VCE (off) = 15 V

50. ICQ = 7 mA

51. VCEQ = 6.32 VFig. 28-19 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 19

53. An example of emitter bias is shown in Fig. 28-23.Fig. 28-23 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 20

54. 07/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 21 TerimaKasih