1. TRANSISTORS AND THYRISTORS
CHAPTER 18
TRANSISTORS AND THYRISTORS

2. BIPOLAR JUNCTION TRANSISTORS (BJTs)
BJT is constructed with three doped semiconductor regions separated by two pn junction
There are three regions :
Emitter
Base
Collector
There are two type of BJT:
npn
pnp

3. Basic construction of BJT

4. Transistor Biasing The BE junction is forward-biased
The BC junction is reverse-biased

5. Transistor Operation

6. Transistor Currents

7. Alpha and Bata
The collector current is equal to times the emitter current
The collector current is equal to the base current multiplied by
has a value between
0.950 and 0.995
has a value between
20 and 200

8. Transistor Voltages

9. VOLTAGE-DIVIDER BIAS
Use only a single dc source to provide forward-reverse bias to the transistor
Resistor R1 and R2 form a voltage divider that provides the base bias voltage

10. Input Resistance at the Base

11. Base Voltage V

12. THE BIPOLAR JUNCTION TRANSISTOR AS AN AMPLIFIER

13. THE BIPOLAR JUNCTION TRANSISTOR AS AN AMPLIFIER
When both junction are forward-biased, the transistor is in the saturation region of its operation
When VCE exceeds 0.7 V, the base-collector junction becomes reverse-biased and the transistor goes into the active or linear region
When IB=0 the transistor is in the cutoff region.
Collector leakage current,
B-E and B-C are reverse-biased I C E O

14. Load Line Operation

15. Quiescent or Q-Point

16. Quiescent or Q-Point

17. Signal (ac) Operation of an Amplifier
The circuit which produces an output signal with the same waveform as input signal but with a greater amplitude is called amplification

18. Signal Operation on the Load Line

19. THE BJT AS A SWITCH
Conditions in cutoff
Conditions in saturation

20. BJT PARAMETERS AND RATINGS
IF the temperature goes up, goes up, and
vice versa.

21. BJT PARAMETERS AND RATINGS
Maximum Transistor Ratings
PD(max) = maximum power dissipation

22. THE JUNCTION FIELD-EFFECT TRANSISTOR (JFET)
The JFET is a type of FET that operates with a reverse-biased junction to control current in the channel

23. Categories FET METAL-OXIDE semiconductor JUNCTION Depletion Depletion
Enhancement
P channel
N channel
P channel
N channel
P channel
N channel

24. JFET Basic Operation
The JFET is always operated with the gate-to-source pn junction reverse-biased

25. JFET Symbols

26. JFET CHARACTERISTICS
IDSS (Drain to Source current with gate shorted) is
maximum drain current occurring for VGS =0 V,
and the value of VDS which ID becomes constant is the
pinch-off voltage

27. Cutoff Voltage
The value of VGS that makes ID approximately zero is the cutoff voltage VGS(off)

28. VGS controls ID.
JFET must be operated between VGS =0 and VGS(off)

29. Comparison of Pinch-Off and Cutoff
Vp is the value of VDS at which the drain current becomes constant and is always measured at VGS =0 V
VGS(off) and Vp are always equal in magnitude but opposite in sign

30. THE METAL-OXIDE SEMICONDUCTOR FET(MOSFET)
Depletion MOSFET (D-MOSFET)
D-MOSFET can be operated either the depletion mode or the enhancement mode

31. Depletion Mode (D-MOSFET)

32. Enhancement Mode (D-MOSFET)

33. D-MOSFET Symbols

34. Enhancement MOSFET(E-MOSFET)

35. E-MOSFET Symbols

36. FET BIASING
Self-Biasing a JFET

37. D-MOSFET Bias

38. Example

39. E-MOSFET Bias Drain-feedback bias Voltage-Divider bias
(a) Drain-feedback bias
(b) Voltage-Divider bias

40. The Other Types of MOSFET
LDMOSFET
VMOS
Dual-gate n-channel
TMOS

41. UNIJUNCTION TRANSISTORS (UJTs)

42. UJT operation
In normal UJT operation, base 2 (B2) and the emitter are biased positive with respect to base 1 (B1), and total resistance between B1 and B2 is RBB
The ratio RB1/RBB is designated η and is defined as the intrinsic standoff ratio
It take an emitter voltage of VB + η *VBB to turn the UJT on, called the peak voltage
When the emitter voltage decreases, it reaches a value called the valley voltage, and the UJT turns off

43. UJT operation

44. UJT Applications

45. THYRISTORS
Thyristors are devices constructed of four layers of semiconductive material such as the silicon-controlled rectifier (SCR), the diac, and the triac
When turned on (triggered), they become low-resistance current paths and remain, although the trigger is removed, until the current is reduced to a certain level or until they are turned off

46. Silicon-Controlled Rectifier (SCRs)
The SCR has three terminals

47. SCR application
Phase control circuit

48. Triacs
The triac is also known as a bidirectional triode thyristor

49. Diacs The diac us a bidirectional device that does not have a gate
It conducts current in either direction when a sufficient voltage, called the breakover potential

50. Transistor packages

51. FIGURE 4-26 Metal cases for general-purpose/small-signal transistors.
Thomas L. Floyd Electronic Devices, 6e and Electronic Devices: Electron Flow Version, 4e
Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

52. FIGURE 4-27 Typical multiple-transistor packages.
Thomas L. Floyd Electronic Devices, 6e and Electronic Devices: Electron Flow Version, 4e
Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

53. FIGURE 4-28 Typical power transistors.
Thomas L. Floyd Electronic Devices, 6e and Electronic Devices: Electron Flow Version, 4e
Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

54. FIGURE 4-29 Examples of RF transistors.
Thomas L. Floyd Electronic Devices, 6e and Electronic Devices: Electron Flow Version, 4e
Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.