BJT AC and DC Analysis This slide condenses the two ways analysis of BJT (AC and DC). At the end of the slide, it has review question answer with answer key as providing.

1. TRANSISTORS
BJT
DC and AC analysis
Prepared by:
Engr. Jesus Rangcasajo
ECE 321 Instructor

2. DC
Biasing

3. Transistor
 Developed in December 23, 1947 in
Bell Laboratories
 By John Bardeen, William Shockley, and
Walter Brattain
 Basically a reSISTOR that amplifies
electrical impulses as they are
TRANsferred from its input to its
output terminals

5.  E – Emitter
 B – Base
 C - Collector
Two pn Junctions:
 Emitter-Base Junction
 Collector-Base Junction

6.  It is a three layer semiconductor
device consisting of either two N-
type and one P-type layers of
materials or two P-type and one N-
type layers of semiconductor
materials.

7. Base
Emitter
Collector
B
C
E

8. Base
 The middle portion which forms two PN junctions between the
emitter and the collector is called the base.
 The base of transistor is thin, as compared to the emitter and is
a lightly doped portion.

 The function of base is to control the flow of charge carrier.
 1017 dopants/ cm3
 Moderately doped

9. Emitter
The portion on one side of transistor that supplies
charge carriers (i.e electron or holes) to the other
two portions
1019 dopants/ cm3
Heavily doped
Collector
 the portion on the other side of the transistor (i.e. the side
opposite to the emitter) that collects the charge carriers
(i.e. electrons or holes).
 1015 dopants/ cm3
 Lightly doped
 The doping level of the collector is in between the heavily
doping of emitter and the light doping of the base.

10. Metal contacts
Epitaxial Planar Structure
Substrate
Collector
Base
Emitter

11. collector collector
basebase
emitter emitter
npn-type pnp-type
n
n
np
p
p

14.  Common Base Configuration
Vi Vo
VEE VCC
E C
B
Ie Ic
RE RC

17. Approximations Values:

18. Alpha (α)
◦ In the dc mode, the levels of IC and IE due to majority
carriers are related by a quantity called alpha and
defined by the following equation:

20.  Common Emitter Configuration
V
i
V
o
I
c
I
e
I
b
R
E
R
B
VB
B
VCC
 The emitter is common
to both input (base-
emitter) and output
(collector-emitter).
 The input is on the base
and the output is on the
collector.

23. Beta (β)
 the ratio of collector current to the base current .
 represents the amplification factor of a transistor. ( is
sometimes referred to as hfe, a term used in transistor
modeling calculations)

25. Relationship between amplification factors α and β

26. Relationship Between Currents
Biasing
Determining the proper biasing arrangement for a common-
emitter npn transistor configuration.

27. Biasing

28.  Common Collector Configuration
Vi
Vo
Ic
Ie
Ib
RE
RB
VBB
VCC
The input is on the base and the
output is on the emitter.

31. Transistor Testing
Checking the forward-
biased base-to-emitter
junction of an npn
transistor
Checking the reverse-
biased base-to-
collector junction of an
npn transistor.
What will happen to our
resistance?
Lower
Resistance
Higher
Resistance

32. Gamma (δ)
◦ the ratio of collector current to the base current .
δ =
Ie
Ib

33. Characteristic Common Base
Common
Emitter
Common
Collector
Power Gain moderate highest moderate
Voltage Gain highest moderate
Lowest (less
than 1)
Current Gain
lowest (less
than1)
moderate highest
Input
Impedance
lowest moderate highest
Output
Impedance
highest moderate lowest
Phase
Inversion
none
180o out of
phase
none
Application RF amplifier universal isolation

34. Bias
 An electrical, mechanical or magnetic
force applied to a device to establish a
desired electrical or mechanical
reference level for its operation.
 Is a DC voltage or current that sets the
operating point for amplifying the AC
signal

35. Recall the following basic relationships for a transistor:

36. The DC input establishes an
operating or quiescent point
called the Q-point.

37. The Three States of Operation
Active or Linear Region Operation
 Base–Emitter junction is forward biased
 Base–Collector junction is reverse biased
Cutoff Region Operation
 Base–Emitter junction is reverse biased
Saturation Region Operation
 Base–Emitter junction is forward biased
 Base–Collector junction is forward biased

38. DC Biasing Circuits
 Fixed-bias circuit
 Emitter-stabilized bias circuit
 Collector-emitter loop
 Voltage divider bias circuit
 DC bias with voltage feedback

39. Fixed Bias Configuration

40. Fixed bias circuit
DC equivalent

41. KVL @ 1
To find:
1 𝑰 𝒃
Solving for base current:
The Base-Emitter Loop

42. Collector-Emitter Loop
KVL @ 2
2
Collector current:

44. Self Bias
 The amplifier produces its own DC voltage
from an IR drop across a resistor in the return
circuit of the common terminal.
 Self bias is probably the type of bias used
most often because it is economical and has
stabilizing effect on the DC level of the output
current.
 Can be emitter stabilized or collector
stabilized.

45. What is the purpose of adding Re – Resistor @
Emitter?
Adding a resistor (Re) to the emitter circuit
stabilizes the bias circuit

46. Improved Biased Stability
Stability refers to a circuit condition in which the currents
and voltages will remain fairly constant over a wide range
of temperatures and transistor Beta values.

47. Base-Emitter Loop

48. Collector-Emitter Loop

49. Voltage-Divider Bias
 The most stable type of circuit biasing.

50. Voltage Divider Bias Analysis
DC Circuit
Thevenin Circuit

51. Thevenin Circuit Analysis

52. Inserting the Thévenin equivalent circuit

53. Signal Bias/Collector Feedback Configuration

54. Base-Emitter Loop

55. Collector-Emitter Loop

56. Emitter Follower (Common Collector) Configuration

58. Common Base Configuration

60. SATURATION
RL
VCC
ACTIVE
CUT- OFF
BREAKDOWN
Q-POINT
LOADLINE
VCE
VCC
IB
IB
IB
IB
IB
IC

61. Active region
 Base-emitter junction is forward biased
and the collector-base junction is reversed
biased.
 Transistor’s active operation as an
amplifier.
Saturation region
 Both junctions are forward biased.
 Switch on operation for the transistor.
Cut off region
 Both junctions are reverse biased.
 Switch off operation for the transistor.

62. Loadline
- Is a straight line drawn on the collector
curves between the cut-off and
saturation points of the transistor.
Q-point (Quiescent point )
- Is the operating point of the transistor
with the time varying sources out of the
circuit.

63. AC & re
Biasing

64.  Re model
 Hybrid 𝜋 𝑚𝑜𝑑𝑒𝑙
 Hybrid equivalent model

65.  an equivalent circuit that represents the
AC characteristics of the transistor
 uses circuit elements that approximate the
behaviour of the transistor.

69. New parameters to be considered:
1. Input impedance – defined from the base to ground
2. Input current – as the base current of the transistor
3. Output current – as the current through the load Rc
4. Output voltage – as the voltage from the collector to
ground
5. Output impedance – across your voltage output

73. 𝒁𝒊 input impedance is “looking into” the system whereas
𝒁 𝒐output impedance is the impedance “looking back into”
the system from the output side.
NOTES:
𝒁𝒊 =
𝑽𝒊
𝑰𝒊
𝒁 𝒐 =
𝑽 𝒐
𝑰 𝒐
SYSTEM

74. The purpose of identifying the important
quantities/parameters is to indicates how output voltage
Vo related to input voltage Vi (Voltage Gain) and Current
Gain

75. 1. Setting all DC sources to zero and
replacing them by a short circuit
equivalent
2. Replacing all capacitors by a short circuit
equivalent
3. Removing all elements by passed by the
short circuit introduced by step 1 and 2
4. Redrawing the network in a more
convenient and logical form

76. Investigate the re model for
CE, CB and CC BJT

77. Circuit Design

78. 𝒁𝒊 =
𝑽𝒊
𝑰𝒊
𝑽𝒊 = 𝑽 𝒃𝒆
𝑰𝒊 = 𝑰 𝒃
𝒁𝒊 =
𝑽𝒊
𝑰𝒊
=
𝑽 𝒃𝒆
𝑰 𝒃

79. We will have to
change the Single
diode to its
EQUIVALENT
RESISTANCE

80. Equivalent
resistance was
simply your
DIODE
RESISTANCE
Diode Resistance
𝒓 𝒅 =
𝟐𝟔𝒎𝑽
𝑰 𝑫
𝒓 𝒆 =
𝟐𝟔𝒎𝑽
𝑰 𝒆

81. Loop 1: To solve 𝑽 𝒃𝒆
1

82. Zi-Zo Circuit Diagram
Notes:
- The more the change in Vce for
the same change in Ic, the larger
will be the output resistance.

83. re model for the common emitter
transistor configuration

87. (a) Determine ICQ and VCEQ.
(b) Find VB, VC, VE, and VBC.

88. Determine VC and VB for the network

89.  Common Emitter Fixed Bias
 Voltage Divider Bias
 CE Emitter Bias (Unbypassed)
 Emitter Follower
 Common Base
 Collector Feedback

90. Common-emitter fixed-bias
configuration

93. 𝒁𝒊 Input Impedance
𝒁 𝒐 Output Impedance
𝑨 𝒗 Voltage Gain

94. 𝑨 𝒗 Voltage Gain
𝒁𝒊 =
𝑽𝒊
𝑰𝒊
𝒁 𝒐 =
𝑽 𝒐
𝑰 𝒐
𝑽𝒊
𝜷𝒓 𝒆 =
𝑽𝒊
𝑰 𝒃
𝑽 𝒐
𝑹 𝒄 ∥ 𝒓 𝒐 =
𝑽 𝒐
−𝜷𝑰 𝒃
𝑽 𝒐 = −𝜷𝑰 𝒃(𝑹 𝒄 ∥ 𝒓 𝒐)
𝑰 𝒃 =
𝑽𝒊
𝜷𝒓 𝒆

95. Phase Relationship
Demonstrating the 180°phase shift between input and output
waveforms.

96. Example
Let us find first the
DC Current…

97. Common-Emitter Voltage-Divider Bias

99. Input impedance: Output impedance:
Voltage gain:

101. Common-Emitter Emitter-Bias Configuration

102. AC re Analysis
Where is the ro?

103. Input impedance:
Output impedance:

104. Voltage gain:

105.  Magical explanation found in the books!

106. Emitter-Follower Configuration

107.  This is also known as the common-collector configuration.
 The input is applied to the base and the output is taken from
the emitter.
 There is no phase shift between input and output.
 The output voltage is always slightly less than the input signal
due to the drop from base to emitter.
 Approx. Av = 1
 Frequently used for IMPEDANCE MATCHING PURPOSES.
- It presents a high impedance at the input and a low impedance
at the output, which is opposite of the standard fixed bias
configuration

108. AC re Model

109. Input impedance:

110. Output impedance:

111. Voltage gain:

112. Darlington Connection

114. Example:

116.  The re model employs a diode
and controlled current source to
duplicate the behavior of a
transistor in the region of
interest.
Note: BJT transistor amplifiers
are current controlled devices.

117.  ℎ𝑖𝑒, ℎ 𝑟𝑒, ℎ 𝑓𝑒, ℎ 𝑜𝑒
 Term “hybrid” was chose due to its mixture of
variables in each equation

119.  We can determine it by isolating each parameters
and examined the relationship!

120. Set 𝐕𝐨 = 𝟎(short circuit the
output terminals, Solve for
𝐡 𝟏𝟏)
𝐡 𝟏𝟏 is the ratio of the input voltage to the input current with the
output terminals shorted, it is called short-circuit input-
impedance parameter
Isolation:
The subscript 11 defines the fact that
the parameter is determined by a ratio
of quantities measured at the input
terminals.

121. Set 𝐈𝐢 = 𝟎(short circuit the
output terminals, Solve for
𝐡 𝟏𝟐)
𝐡 𝟏𝟐 the ratio of the input voltage to the output voltage with the
input current equal to zero., it is open-circuit reverse transfer
voltage ratio parameter
Isolation:
The subscript 12 reveals that the
parameter is a transfer quantity
determined by a ratio of input to
output measurements

122. Set 𝑽 𝒐 = 𝟎(short circuit the
output terminals, Solve for
𝐡 𝟐𝟏)
𝐡 𝟐𝟏 is the ratio of the output current to the input current with the
output terminals shorted, it is short-circuit forward transfer
current ratio parameter
Isolation:

123. Set 𝑰 𝟏 = 𝟎(short circuit the
output terminals, Solve for
𝐡 𝟐𝟐)
𝐡 𝟐𝟐 the ratio of the output current to the output voltage, it is the
output conductance parameter and is measured in siemens (S),
it is open-circuit output admittance parameter
Isolation:

124. 𝐡 𝟏𝟏
𝐡 𝟏𝟐
𝐡 𝟐𝟏
𝐡 𝟐𝟐

125. Complete hybrid equivalent circuit
𝐡𝐢𝐞 = 𝛃𝐫𝐞
𝐡 𝐟𝐞 = 𝛃 𝐚𝐜
𝐡𝐢𝐛 = 𝐫𝐞
𝐡 𝐟𝐛 = −𝛂 = −𝟏
𝐫𝐨 =
𝟏
𝐡 𝐨𝐞

126. Common Emitter

127. a. Common emitter hybrid equivalent circuit.

128. 𝒓 𝒆:
𝐫𝐞 =
𝟐𝟔𝐦𝐕
𝐈 𝐄
=
𝟐𝟔𝐦𝐕
𝟐. 𝟓𝐦𝐀
= 𝟏𝟎. 𝟒 𝛀
𝒉𝒊𝒆:
𝐡𝐢𝐞 = 𝛃𝐫𝐞 = 𝟏𝟒𝟎 𝟏𝟎. 𝟒
= 𝟏. 𝟒𝟓𝟔𝐤𝛀
𝐡 𝐟𝐞 = 𝛃 𝐚𝐜
𝒓 𝒐:
𝐫𝐨 =
𝟏
𝐡 𝐨𝐞
=
𝟏
𝟐𝟎𝛍𝐒
= 𝟓𝟎𝐤𝛀

129. Common Base

130. 1. Draw the DC, re model and h-model analysis in
each config below; and write the parameters of the
approximate hybrid equivalent circuit of the
following:
a. Fixed Bias Configuration
b. Voltage Divider Configuration
c. Emitter follower Configuration
2. The voltage gain, current gain, input impedance and
Output Impedance of a complete hybrid equivalent
model.

131. Friday
May 12, 2017
Coverage:
- BJT AC Analysis

133. 1. Which of the following is necessary for a
transistor action
a. the base region must be very wide
b. the base region must be very narrow
c. the base region must be made from insulating
materials
d. the collector region must be heavily doped

134. 2. It is the most stable type of circuit biasing
a. self-bias
b. signal bias
c. voltage-divider bias
d. fixed bias

135. 3. The quiescent state of a transistor implies
a. zero bias
b. no output
c. no distortion
d. no input signal

136. 4. Which of the following device is unipolar?
a. FET
b. BJT
c. Zener diode
d. LED

137. 5. The parameter HFE corresponds to
a. βDC
b. βAC
c. r’e
d. r’c

138. 6. If the DC emitter current in a certain transistor
amplifier is 3 mA, the approximate value of r’e
is
a. 3 KΩ
b. 3 Ω
c. 8.33 Ω
d. .33 KΩ
r’e = 26 mV
3 mA
= 8.6667 ΩSolution:

139. 7. What is the current gain of a common base
circuit called?
a. gamma
b. delta
c. bravo
d. alpha

140. 8. The name of the very first transistor
a. diode
b. junction transistor
c. point contact transistor
d. triode

141. 9. Region in a transistor that is heavily doped
a. collector
b. emitter
c. base
d. gate

142. 10. Which are the three terminals of a bipolar
transistor?
a. Cathode, plate and grid
b. Base, collector and emitter
c. Input, output and ground
d. Gate, source and sink

143. 11. A transistor in which n-type and p-type
materials are used is called
a. Unijunction
b. TTL
c. Bipolar
d. FET

144. 12. The region in an electronic transistor that is
lightly doped and very thin is referred to the
a. Collector-base
b. Collector
c. Base
d. Emitter

145. 13. In the BJT schematic symbol, the arrow
a. Points from p-type to n-type
b. Points from north to south
c. Points from n-type to p-type
d. Points from south to north

146. 14. _____ is the region in the transistor that is
heavily doped
a. Collector
b. Ground
c. Base
d. Emitter

147. 15. The arrow in the symbol of a transistor
indicates the direction of
a. Electron current in the collector
b. Donor ion current
c. Electron current in the emitter
d. Hole current in the emitter

148. 16. ____ is the term used to express the ratio of
change in the DC collector current to a
change in base current in a bipolar
transistor
a. Gamma
b. Beta
c. Alpha
d. Delta

149. 17. Solve the collector current if the base current is
200mA and the current gain is 20
a. 10 A
b. 4 A
c. 1 A
d. 40 A

150. 18. The flow of electrons in an NPN transistor
when used in electronic circuits is from
a. Collector to emitter
b. Collector to base
c. Emitter to collector
d. Base to emitter

151. 19. A transistor acts as _____ when saturated
a. Open circuit
b. Very low resistance
c. Very high resistance
d. Variable resistance

152. 20. For a BJT, the BE junction is reverse biased
and BC forward biased. The BJT is in what
operating mode?
a. Forward active
b. Cut-off
c. Reverse active
d. Saturation

153. 21. Line representing all the DC operating
points of the BJT.
a. DC loadline
b. Collector curve
c. AC loadline
d. Operating line

154. 22. What is another name for base bias?
a. Fixed bias
b. Gate bias
c. Emitter bias
d. Beta bias

155. 23. What is the most stable type of biasing
a. Current feedback
b. Fixed bias
c. Voltage divider
d. Voltage feedback

156. 24. The h-parameter hf is a
a. Resistance
b. Reverse voltage gain
c. Conductance
d. Forward current gain

157. 25. Among the common emitter h-parameters,
which is the smallest?
a. hie
b. hre
c. hfe
d. hoe

158. 26. Which of the BJT amplifier configuration has
the highest power gain?
a. CE
b. CC
c. CB
d. Emitter follower

159. 27. Another name for common collector
a. Collector follower
b. Base follower
c. Emitter follower
d. Collector divider

160. 28. Which of the BJT amplifier configuration can
be used as a buffer?
a. CB
b. CS
c. CC
d. CE

161. 29. Which transistor configuration has the
highest input resistance?
a. Common base
b. Common emitter
c. Common collector
d. Common transistor

162. 30. Capacitor used to established an ac ground
at a specific point in a circuit
a. Electrolytic
b. Coupling
c. Bypass
d. Choke

163. 31. ____ is a unipolar semiconductor device
which the current is carried by the majority
carriers only
a. Field-effect transistor
b. Point-contact transistor
c. Zener diode
d. Junction transistor

164. 32. The two types of bipolar transistor are:
a. PN and NP
b. PNP and NPN
c. PPN and NNP
d. N and P

165. 33. The three terminals of a bipolar junction
transistor are called
a. p, n, p
b. n, p, n
c. Input, output and ground
d. Base, emitter and collector

166. 36. The largest region of a bipolar transistor is
the
a. Base
b. Emitter
c. Collector
d. N-region

167. 37. The emitter of the transistor is generally
doped the heaviest because it
a. Has to dissipate maximum power
b. Has to supply the charge carriers
c. Is the first region of the transistor
d. Must posses low resistance

168. 38. In a PNP transistor, the p-regions are
a. Base and emitter
b. Base and collector
c. Emitter and collector
d. None of these

169. 39. During normal operation, the highest
percentage of electrons leaves a NPN
transistor from which region?
a. Base
b. Emitter
c. Collector
d. N-region

170. 40. For operation as an amplifier, the base of an
NPN transistor must be
a. Positive with respect to the emitter
b. Negative with respect to the emitter
c. Positive with respect to the collector
d. 0 V

171. 41. A bipolar transistor’s majority current
carriers are:
a. Electrons
b. Holes
c. Dependent upon the type of transistor
d. Always both electrons and holes

172. 42. In which region is a bipolar transistor
normally operated
a. Saturation
b. Cut-off
c. Linear
d. Beta

173. 43. A transistor has a common base forward
circuit gain hFE=0.98 the DC forward current
gain hFE is
a. 49
b. 50
c. 98
d. Not determinable from the data given

174. 44. When the transistor is fully switched on, it
is to be
a. Shorted
b. Open
c. Saturated
d. Cut-off

175. 45. In which operating region should normal
figures calculated
a. Saturation
b. Breakdown
c. Cut-off
d. Active

176. 46. Which transistor circuit arrangement
produces the highest power gain?
a. Common base
b. Common collector
c. Common emitter
d. A transistor’s power gain is the same in any
circuit

177. 47. The DC loadline of a transistor circuit
a. Has a negative slope
b. Is a curved line
c. Gives graphic relation between IC and IB
d. Does not contain the Q-point

178. 48. The βDC of a transistor is its
a. Current gain
b. Voltage gain
c. Power gain
d. Internal resistance

179. 49. If in a bipolar junction transistor, Ib = 100
μA and Ic = 10 mA, what is the value of its
beta?
a. 0.1
b. 10
c. 100
d. None of these

180. 50. If Ic is 50 times larger than Ib then βDC is
a. 0.02
b. 100
c. 50
d. 500

181. 51. If βDC is 100, the value of αdc is
a. 99
b. 0.99
c. 101
d. 0.01

182. 52. The approximate voltage across the
forward-biased base-emitter junction of a
silicon BJT is
a. 0 V
b. 0.7 V
c. 0.3 V
d. Vbb

183. 53. If the output of a transistor amplifier is 5
Vrms and the input is 100 Vrms, the voltage
gain is
a. 5
b. 500
c. 50
d. 100

184. 54. When operated in cut-off and saturation, the
transistor acts like
a. Linear amplifier
b. A switch
c. A variable capacitor
d. A variable resistor

185. 55. The unit of measurement for transconductance
is
a. Ohm
b. Mho
c. Siemens
d. B or C

186. 56. Which circuit produces a voltage gain that is
always less than unity?
a. Common-drain
b. Common-gate
c. Common-source
d. All of the above

187. 57. Which of the following circuits generally has
the greatest gain?
a. Common-source
b. Common-gate
c. Common-drain
d. None of the above

188. 58. In a PNP transistor, the p-regions are
a. Base and emitter
b. Base and collector
c. Emitter and collector
d. Wala lang

189. 59. In cut-off, VCE is
a. 0 V
b. Minimum
c. Maximum
d. Equal to VCC

190. 60. In saturation VCE is
a. 0.7 V
b. Equal to VCC
c. Minimum
d. Maximum

191. 61. To saturate a BJT
a. IB = IC
b. IB > IC(SAT) / βDC
c. VCC must be at least 10 V
d. The emitter must be grounded

192. 62. Once in saturation, a further increase in
base current will
a. Cause the collector current to increase
b. Not affect the collector current
c. Cause the collector current to decrease
d. Turn the transistor off

193. 63. If the base-emitter junction is open, the
collector voltage is
a. VCC
b. 0 V
c. Floating
d. 0.2 V

194. 64. The maximum value of collector current in a
biased transistor is
a. BDCIB
b. IC(SAT)
c. Greater than IE
d. IE - IB

195. 65. Ideally, a dc loadline is a straight line drawn
on the collector characteristic curves
between
a. The Q-point and cut-off
b. The Q-point and saturation
c. VCE(CUT-OFF)
d. IB = 0 and IB = IC / βDC

196. 66. If a sinusoidal voltage is applied to the base of
a biased npn transistor and the resulting
sinusoidal collector voltage is clipped near zero
volts, the transistor is
a. Being driven into saturation
b. Being driven into cutoff
c. Operating nonlinearly
d. Answers A and C

197. 67. The disadvantage of a base bias is that
a. It is very complex
b. It produces voltage gain
c. It is too beta dependent
d. It produces high leakage current

198. 68. Emitter bias is
a. Essentially independent of βDC
b. Very dependent on βDC
c. Provides a stable bias point
d. Answers A and C

199. 69. The input resistance at the base of a biased
transistor depends mainly on
a. βDC
b. RB
c. RE
d. βDC and RE

200. 70. In a voltage-divider biased transistor
circuit, RIN(BASE) can generally be neglected in
calculations when
a. RIN(BASE) > R2
b. R2 > 10RIN(BASE)
c. RIN(BASE) > 10R2
d. R1 << R2

201. 71. In a certain voltage-divider biased npn
transistor, VB is 2.95 V. The dc emitter
voltage is approximately
a. 2.25 V
b. 2.95 V
c. 3.65 V
d. 0.7 V

202. 72. voltage-divider bias
a. Cannot be independent of βDC
b. Can be essentially independent of βDC
c. Is not widely used
d. Requires fewer components than all the other
methods

203. 73. In a voltage-divider biased npn transistor, if
the upper voltage-divider resistor (the one
connected to VCC) opens,
a. The transistor goes into cut-off
b. The transistor goes into saturation
c. The transistor burns out
d. The supply voltage is too high

204. 74. A small signal amplifier
a. Uses only a small portion of its loadline
b. Always has an output signal in the mV range
c. Goes into saturation once on each input cycle
d. Is always a common-emitter amplifier

205. 75. If the DC emitter current in a certain
transistor amplifier is 3 mA, the
approximate value of r’e is
a. 3 KΩ
b. 3 Ω
c. 8.33 Ω
d. 0.33 Ω

206. 76. A transistor in which n-type and p-type
materials are used is called
a. Unijunction
b. Bipolar
c. TTL
d. FET

207. 77. In the PNP transistor ____ are the majority
carriers
a. Electrons
b. Holes
c. Donor atoms
d. Acceptor atoms

208. 78. Biasing represents ____ condition
a. AC
b. DC
c. AC and DC
d. Neither AC nor DC

209. 79. The following relationships between alpha
and beta are true except
a. Beta = alpha/ (1- alpha)
b. Alpha = beta/ (beta - 1)
c. Alpha = beta/ (beta + 1)
d. (1- alpha) = 1/ (1 + beta)

210. 80. The circuit that provides the best
stabilization of operating point is
a. Base bias
b. Collector feedback bias
c. Voltage divider bias
d. Emitter feedback bias

211. 81. The smallest of the four h-parameters of
the transistor is
a. Hr and Ho
b. Hi and Ho
c. Hr and Hf
d. Hi and Hf

212. 1. Why does base bias produce such
an unstable Q point?
2. When a transistor is operating in the
active region, why is the collector
considered a current source?

213. Electronic Devices and Circuit Theory, 10th
Ed., R. Boylestad & L. Nashelsky, Copyright
©2009 by PEARSON Education, Inc.