1. Bipolar Junction Transistor Basics
BJTs B C E

2. A transistor consists of two PN junctions
A transistor consists of two PN junctions. Thus a transistor is like two PN – junction diodes connected back to back.

3. The BJT – Bipolar Junction Transistor
Note: Normally Emitter layer is heavily doped, Base layer is lightly doped and Collector layer has Moderate doping.
The Two Types of BJT Transistors:
npn
pnp n p n p n p E C E C C C
Cross Section
Cross Section B B B B
Schematic Symbol
Schematic Symbol E E

4. BJT Current Equation n p n p n p IE = IB + IC IE = IB + IC IE IC IE IC-
VCE + +
VEC - E C E C - - + +
VBE
VBC IB
VEB
VCB IB - - + + B B
n p n
IE = IB + IC
p n p
IE = IB + IC

5. Operation of PNP transistor

6. Operation of NPN transistorIc C n
Recombination
VCB + _
Electrons
+ Holes B p + + IB -
VBE - _ - n E IE

7. Three Possible Configurations of BJT
Biasing the transistor refers to applying voltages to the transistor to achieve certain operating conditions.
1. Common-Base Configuration (CB) : input = VEB & IE
output = VCB & IC
2. Common-Emitter Configuration (CE): input = VBE & IB
output= VCE & IC
3. Common-Collector Configuration (CC) :input = VBC & IB
(Also known as Emitter follower) output = VEC & IE

8. Transistor Circuit Configurations

9. Common Base Configuration

10. Common Base Configuration Input Characteristics

11. Common-Base (CB) Characteristics Vc- Ic (output) Characteristic CurvesmA
Breakdown Reg. 6
Active Region IE 4
Saturation Region
IE=2mA 2
IE=1mA
Cutoff
IE = 0
VCB
0.8V 2V 4V 6V 8V
Early Effect

12. Common Emitter Configuration

13. Common Emitter Configuration Input Characteristics

14. Common Emitter Configuration Output Characteristics
BJT’s have three regions of operation:
1) Active - BJT acts like an amplifier (most common use)
2) Saturation - BJT acts like a short circuit
3) Cutoff - BJT acts like an open circuit

15. Common Emitter Configuration Output Characteristics
Region of Operation
Description
Active
Small base current controls a large collector current
Saturation
VCE(sat) ~ 0.2V, VCE increases with IC
Cutoff
Achieved by reducing IB to 0, Ideally, IC will also be equal to 0.
Active Region IB
VCE
Saturation Region
Cutoff Region
IB = 0

16. Common-Collector Configuration

17. Common-Collector Input Characteristics

18. Common-Collector BJT Characteristics Emitter-Current Curves
The Common-Collector biasing circuit is basically equivalent to the common-emitter biased circuit except instead of looking at IC as a function of VCE and IB we are looking at IE.
Also, since  ~ 1, and  = IC/IE that means IC~IE IE
Active Region IB
VCE
Saturation Region
Cutoff Region
IB = 0

19. Comparison

20. BJT Amplifiers

21. Single Stage Amplifiers CE Amplifier

22. CE Amplifier

23. CE Amplifier

24. Input & Output Voltages of CE Amplifier

25. PUZZLE
The ages of a father and son add up to 66. The father's age is the son's age reversed. How old could they be?

26. ANS:
Father 51, son 15 Father 42, son 24 Father 60, son 06

27. PUZZLE
Ram sat with his friends in the Chinnaswamy stadium in Bangalore to watch the 100 metres running race organized by the Asian athletics Association. Five rounds were run. After every round half the teams were eliminated. Finally, one team wins the game. How many teams participated in the race?

28. ANS:32

29. A grand father has 3 grand children
A grand father has 3 grand children. Age difference of two children among them is 3. Eldest child age is 3 times the youngest child’s age and the eldest child age is two year more than the sum of age of other two children. What is the age of the eldest child?

30. ANS:15

31. READING

32. DRAW MINDMAP

33. SUMMARY

34. Moulting (Drawing mind map on the board)

35. Moulting (presentation within the group)