1. J.-B. Seo, S. Srirangarajan, S.-D. Roy, and S. Janardhanan
Course Instructors:
J.-B. Seo, S. Srirangarajan, S.-D. Roy, and S. Janardhanan
Department of Electrical Engineering, IITD

2. Diode: Clamping circuit
During negative half-cycle, Diode is ‘ON’
The capacitor charges up to
During positive half-cycle, Diode is ‘OFF’

3. Diode: Clamping circuit
During positive half-cycle, Diode is ‘OFF’
The capacitor charges up to
No charging. Instead, discharging occurs up to

4. Diode: Clamping circuit
During positive half-cycle, Diode is ‘OFF’
The capacitor charges up to
No charging. Instead, discharging occurs up to

5. Diode: Clamping circuit
During positive half-cycle, Diode is ‘OFF’
The capacitor charges up to
No charging. Instead, discharging occurs up to

6. Diode: Clamping circuit
During positive half-cycle, Diode is ‘OFF’
The capacitor charges up to
No charging. Instead, discharging occurs up to

7. Diode: Clamping circuit
During positive half-cycle, Diode is ‘OFF’
The capacitor charges up to
No charging. Instead, discharging occurs up to

8. Diode: Clamping circuit
During positive half-cycle, Diode is ‘OFF’
The capacitor charges up to
No charging. Instead, discharging occurs up to

9. Diode: Clamping circuit
During positive half-cycle, Diode is ‘OFF’
The capacitor charges up to
No charging.
Instead, discharging occurs
up to

10. Diode: Clamping circuit
During negative half-cycle, Diode is ‘ON’
The capacitor charges up to
During positive half-cycle, Diode is ‘OFF’

11. Example 1
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V. Determine Vo.
Thursday, November 29, 2018

12. Example 1
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V. Determine Vo.
Thursday, November 29, 2018

13. Example 1
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V. Determine Vo.
Thursday, November 29, 2018

14. Example 1
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V. Determine Vo.
Thursday, November 29, 2018

15. Example 1
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V. Determine Vo.
Thursday, November 29, 2018

16. Example 1
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V. Determine Vo.
Thursday, November 29, 2018

17. Example 1
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V. Determine Vo.
Infeasible system
Thursday, November 29, 2018

18. Example 2
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V and Vcc =6 V Determine Vo.
Thursday, November 29, 2018

19. Example 2
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V and Vcc =6 V Determine Vo.
Thursday, November 29, 2018

20. Example 2
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V and Vcc =6 V Determine Vo.
Thursday, November 29, 2018

21. Example 2
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V and Vcc =6 V Determine Vo.
Thursday, November 29, 2018

22. Example 2
Consider the Si diode in the circuit. Let V1 = 5 V and V2 = 0 V and Vcc =6 V Determine Vo.
Thursday, November 29, 2018

23. Diode: Clamping circuit
If , Diode is ‘ON’
The capacitor charges up to
If , Diode is ‘OFF’

24. Diode: Clamping circuit
If , Diode is ‘ON’
The capacitor charges up to
If , Diode is ‘OFF’

25. Diode: Clamping circuit
If , Diode is ‘ON’
Capacitor discharging, depending on RC
The capacitor charges up to
If , Diode is ‘OFF’

26. Diode: Clamping circuit

27. Transistor: transfer resistor+ + — + — + — + — + — — — — — + + + — + — + — + — + — + — + — + + + + + + + — + + + + + + + + + + + + + + + — + + + + + + + + + + + + + + + — + + + + + + + + — + + +
Circuit symbol
Doping order
Nemitter > Ncollector > Nbase
Thickness order
Tcollector >Temitter >Tbase

28. Transistor: transfer resistor+ + — + — + — + — + — — — — — + + + — + — + — + — + — + — + — + + + + + + + — + + + + + + + + + + + + + + + — + + + + + + + + + + + + + + + — + + + + + + + + — + + +
Circuit symbol
Doping order
Nemitter > Ncollector > Nbase
Thickness order
Tcollector >Temitter >Tbase

29. Transistor: transfer resistor+ + — + — + — + — + — — — — — + + + — + — + — + — + — + — + — + + + + + + + — + + + + + + + + + + + + + + + — + + + + + + + + + + + + + + + — + + + + + + + + — + + +
Circuit symbol
Doping order
Nemitter > Ncollector > Nbase
Thickness order
Tcollector >Temitter >Tbase

30. Transistor: transfer resistor— +
Circuit symbol
Doping order
Nemitter > Ncollector > Nbase
Thickness order
Tcollector >Temitter >Tbase

31. Transistor: transfer resistor+ + + + + + — — — — — — — — + + — + — + — + — + — + — + + + + + + — + + + + + + + + + + + + + — + + + + + + + + + + + + + — + + + + + + + — +
Circuit symbol
Doping order
Nemitter > Ncollector > Nbase
Thickness order
Tcollector >Temitter >Tbase

32. Transistor: transfer resistor— +
Doping order
Nemitter > Ncollector > Nbase
Thickness order
Tcollector >Temitter >Tbase
Circuit symbol:

33. Transistor: transfer resistor— +

34. Transistor: transfer resistor— +

36. Transistor: transfer resistor+ + + + + + — — — + + — — + + — + + + + + + + + + — + + + + + + + + + + + + + — + + + + + + + — + + + + + + — + + + + + + + — + — — — — —

37. BJT- Basic Working
Forward bias of EB Jcn. causes electrons to diffuse from emitter into base.
As base region is very thin, the majority of electrons diffuse to the edge of the deple-tion region of CB Jcn., and then are swept to the collector by the electric field of the reverse-biased CB Jn.
Small fraction of the electrons recombine with holes in base region.
Holes are also injected from base to emitter region. (4) << (1).
The two-carrier flow from [(1) and (4)] forms the emitter current (IE) ①

38. BJT- Basic Working
Forward bias of EB Jcn. causes electrons to diffuse from emitter into base.
As base region is very thin, the majority of electrons diffuse to the edge of the deple-tion region of CB Jcn., and then are swept to the collector by the electric field of the reverse-biased CB Jn.
Small fraction of the electrons recombine with holes in base region.
Holes are also injected from base to emitter region. (4) << (1).
The two-carrier flow from [(1) and (4)] forms the emitter current (IE) ① ②

39. BJT- Basic Working
Forward bias of EB Jcn. causes electrons to diffuse from emitter into base.
As base region is very thin, the majority of electrons diffuse to the edge of the deple-tion region of CB Jcn., and then are swept to the collector by the electric field of the reverse-biased CB Jn.
Small fraction of the electrons recombine with holes in base region.
Holes are also injected from base to emitter region. (4) << (1).
The two-carrier flow from [(1) and (4)] forms the emitter current (IE) ① ② ③

40. BJT- Basic Working ① ② ③ ④
Forward bias of EB Jcn. causes electrons to diffuse from emitter into base.
As base region is very thin, the majority of electrons diffuse to the edge of the deple-tion region of CB Jcn., and then are swept to the collector by the electric field of the reverse-biased CB Jn.
Small fraction of the electrons recombine with holes in base region.
Holes are also injected from base to emitter region. (4) << (1).
The two-carrier flow from [(1) and (4)] forms the emitter current (IE) ① ② ③ ④

41. Transistor: transfer resistor+ + + + — — — — — + — + — — + + — + — + — + — + — + — + + + + + + — + + + + + + + — + + + + + + — + + + + + + + — — + + + + + + — + + + + + + + — + — —
current gain !

42. Transistor: transfer resistor+ + + + — — — — — + — + — — + + — + — + — + — + — + — + + + + + + — + + + + + + + — + + + + + + — + + + + + + + — — + + + + + + — + + + + + + + — + — —
current gain !

43. Transistor: transfer resistor+ + + + — — — — — + — + — — + + — + — + — + — + — + — + + + + + + — + + + + + + + — + + + + + + — + + + + + + + — — + + + + + + — + + + + + + + — + — —
current gain !

44. Transistor: transfer resistor+ + + + — — — — — + — + — — + + — + — + — + — + — + — + + + + + + — + + + + + + + — + + + + + + — + + + + + + + — — + + + + + + — + + + + + + + — + — —
current gain !

45. Both forward biased + + + + + + — + + + + + + + + + + + + — + + + + +
Saturation:

46. Transistor: transfer resistor— — — — — + + — — — — — + + — + — — — + + — — — — — — — — + + — — — — — + — — — + + — — — — — — +

47. BJT operation mode

48. BJT operation mode

49. BJT operation mode

50. BJT operation mode

51. BJT operation mode 

52. BJT operation mode  

53. BJT operation mode  
Forward active
cutoff
Saturation

54. BJT operation mode  
Forward active
cutoff
Saturation

55. Summary of BJT operation modes
npn BJT
pnp BJT
Forward active region (mode)

56. Summary of BJT operation modes
npn BJT
pnp BJT
Saturation region (mode)

57. Summary of BJT operation modes
npn BJT
pnp BJT
Cutoff region (mode)

58. Why back-to-back diode model can’t be used?+ – + –

59. Why back-to-back diode model can’t be used?+ – + –

60. Why back-to-back diode model can’t be used?+ – + –

61. Why back-to-back diode model can’t be used?+ – + – + –

62. Why back-to-back diode model can’t be used?+ – + – + – + –

63. Example – 1
Less than turn-on voltage
 The input is high voltage

64. Example – 1  The input is low voltage  The input is high voltage
Less than turn-on voltage
 The input is high voltage

65. Example – 1  The input is low voltage  The input is high voltage
Less than turn-on voltage
 The input is high voltage

66. Example – 1  The input is low voltage  The input is high voltage
Less than turn-on voltage
 The input is high voltage

67. Example – 1  The input is low voltage  The input is high voltage
Less than turn-on voltage
 The input is high voltage

68. Example – 1  The input is low voltage  The input is high voltage
Less than turn-on voltage
 The input is high voltage

69. Example – 1  The input is low voltage  The input is high voltage
Less than turn-on voltage
 The input is high voltage

70. Example – 1
 The input is high voltage:
Cutoff
0.5 1 5
Saturation

71. Example – 2

72. Example – 2

73. Example – 2

74. Example – 2

75. Example – 2

76. Example – 3

77. Example – 3

78. Example – 3

79. Example – 3
Not forward active region

80. Example – 3
Not forward active region

81. Example – 3
Not forward active region

82. Example – 3
Not forward active region

83. Example – 3

84. Example – 3
NOR gate

85. BJT as an amplifier
Let the transistor work in forward-active region

86. BJT as an amplifier
Let the transistor work in forward-active region

87. BJT as an amplifier
Let the transistor work in forward-active region

88. BJT as an amplifier Let the transistor work in forward-active region
AC input signal should not affect the transistor (DC) biasing!

89. BJT as an amplifier
Stable biasing

90. Voltage divider biasing circuit
BJT as an amplifier: application
Voltage divider biasing circuit
Stage 1 amplifier
Stage 2
amplifier
Bypassing capacitor
DC blocking capacitors

91. BJT Amplifier circuit
Configuration
Common-base, common-emitter, common-collector
Determine which one is amplified, e.g., voltage, current, or both.
DC Biasing circuit
Construct a stable forward-active region (mode)
Small-signal model
Analyze BJT circuit with AC signal (small-amplitude, various frequencies)

92. BJT configuations: two-port network
Common base configuration
Common emitter configuration
Common collector configuration
Characteristic
Common Base
Common Emitter
Common Collector
Input impedance
Low
Medium
High
Output impedance
Very high
Phase shift
Voltage gain
Current gain
Power gain

93. BJT configuations: two-port network
Common base configuration
Common emitter configuration
Common collector configuration
Characteristic
Common Base
Common Emitter
Common Collector
Input impedance
Low
Medium
High
Output impedance
Very high
Phase shift
Voltage gain
Current gain
Power gain

94. BJT configuations: two-port network
Common base configuration
Common emitter configuration
Common collector configuration
Characteristic
Common Base
Common Emitter
Common Collector
Input impedance
Low
Medium
High
Output impedance
Very high
Phase shift
Voltage gain
Current gain
Power gain

95. BJT: Small-signal model
Input
Output

96. Common base configuration (P.371)
Not good for current amplification
But reasonable voltage gain
Saturation

97. Common emitter configuration
Reasonable current AND voltage gain
High power gain

98. Common emitter configuration: p.372

99. Example: p. 374 (Common-Emitter)

100. Example: p. 374 (Common-Emitter)

101. Example: p. 374

102. Example: p. 374

103. BJT biasing schemes
Objective is to provide (stable) forward-active mode.
Fixed current bias
Collector-to-Base feedback resistor
Self-Bias
Current-mirror

104. BJT biasing: fixed current bias
Provide the desired dc base current from

105. BJT biasing: fixed current bias
Provide the desired dc base current from

106. BJT biasing: fixed current bias
Provide the desired dc base current from

107. BJT biasing: fixed current bias
Provide the desired dc base current from

108. BJT biasing: Collector-to-Base feedback resistor

109. BJT biasing: Collector-to-Base feedback resistor

110. BJT biasing: Collector-to-Base feedback resistor

111. BJT biasing: Collector-to-Base feedback resistor

112. BJT biasing: Self-bias+ –

113. BJT biasing: Self-bias

114. BJT biasing: Self-bias

115. BJT biasing: Self-bias

116. BJT biasing: Self-bias
— ①
— ②
Combining ① and ②

117. BJT biasing: Self-bias
— ①
— ②
Combining ① and ②

118. BJT biasing: Self-bias
— ①
— ②
Combining ① and ②

119. BJT biasing: Current mirror

120. BJT: Small-signal model
Input
Output

121. BJT: Small-signal model
Input
Output

122. BJT: Small-signal model
Input
Output

123. BJT: Small-signal model
Input
Output

124. Example – 1
→ This dc gain will be effective for ac gain

125. Example – 1
→ This dc gain will be effective for ac gain

126. Example – 1
→ This dc gain will be effective for ac gain

127. Example – 1

128. Example – 1

129. Example – 2

130. Example – 2
; The transistor works at the forward active mode.

131. Example – 2
a circuit terminal connected to a constant dc source can always be considered as a signal ground in small-signal analysis : superposition theorem for linear operating point.

132. Example – 2

133. Example – 2

134. BJT: Two-port model
How can we generalize the model for any configuration and any small-signal application?
Linear
two-port
network
Y Parameters
Z Parameters
h parameters
g parameters
h parameters

135. BJT: Two-port model
How can we generalize the model for any configuration and any small-signal application?
Linear
two-port
network
Y Parameters
Z Parameters
h parameters
g parameters
h parameters

136. BJT: Two-port model
How can we generalize the model for any configuration and any small-signal application?
Linear
two-port
network
Y Parameters
Z Parameters
h parameters
g parameters
h parameters

137. BJT: Two-port model

138. BJT: Two-port model
(Data sheet provides this value)

139. BJT: Two-port model Y Y X X Z Z Z
Resistance
Ratio
Admittance

140. Example – 1 By current division, we can get Resistance Ratio
Admittance
By current division, we can get

141. Example – 1 By current division, we can get Resistance Ratio
Admittance
By current division, we can get

142. Example – 1
Resistance
Ratio
Admittance
The output voltage is

143. Example – 1 The output voltage is The input voltage should be
Resistance
Ratio
Admittance
The output voltage is
The input voltage should be

144. Example – 2

145. Example

146. Example - 2
Forward active region !

147. Example - 2
Forward active region !

148. Example - 2
Forward active region !

149. Example - 2
Forward active region !

150. Example - 2 Forward active region ! This part should be reverse-biased
to confirm the forward active region
Forward active region !

151. BJT amplifier
Let the transistor work in forward-active region

152. BJT: Configurations with small-signal model
Common-base configuration
DC-biasing is omitted

153. Common emitter configuration: p.372

154. Common emitter configuration: p.372

155. Common emitter configuration: p.372