Bipolar Junction Transistor (BJT) CHAPTER 3 Bipolar Junction Transistor (BJT) Notes | EduRev

: Bipolar Junction Transistor (BJT) CHAPTER 3 Bipolar Junction Transistor (BJT) Notes | EduRev

 Page 1


Bipolar Junction Transistor 
(BJT) 
CHAPTER 3 
Page 2


Bipolar Junction Transistor 
(BJT) 
CHAPTER 3 
Introduction 
• The basic of electronic system nowadays is 
 semiconductor device.  
• The famous and commonly use of this device 
is BJTs 
 (Bipolar Junction Transistors). 
• It can be use as amplifier and logic switches. 
• BJT consists of  three terminal: 
 ? collector : C 
 ? base : B 
 ?emitter : E 
• Two types of BJT : pnp and npn 
 
Page 3


Bipolar Junction Transistor 
(BJT) 
CHAPTER 3 
Introduction 
• The basic of electronic system nowadays is 
 semiconductor device.  
• The famous and commonly use of this device 
is BJTs 
 (Bipolar Junction Transistors). 
• It can be use as amplifier and logic switches. 
• BJT consists of  three terminal: 
 ? collector : C 
 ? base : B 
 ?emitter : E 
• Two types of BJT : pnp and npn 
 
Transistor Construction 
• 3 layer semiconductor device consisting: 
• 2 n- and 1 p-type layers of material ? npn transistor 
• 2 p- and 1 n-type layers of material ?pnp transistor 
• The term bipolar reflects the fact that holes and 
electrons participate in the injection process into the 
oppositely polarized material 
• A single pn junction has two different types of bias: 
• forward bias 
• reverse bias 
• Thus, a two-pn-junction device has four types of bias. 
Page 4


Bipolar Junction Transistor 
(BJT) 
CHAPTER 3 
Introduction 
• The basic of electronic system nowadays is 
 semiconductor device.  
• The famous and commonly use of this device 
is BJTs 
 (Bipolar Junction Transistors). 
• It can be use as amplifier and logic switches. 
• BJT consists of  three terminal: 
 ? collector : C 
 ? base : B 
 ?emitter : E 
• Two types of BJT : pnp and npn 
 
Transistor Construction 
• 3 layer semiconductor device consisting: 
• 2 n- and 1 p-type layers of material ? npn transistor 
• 2 p- and 1 n-type layers of material ?pnp transistor 
• The term bipolar reflects the fact that holes and 
electrons participate in the injection process into the 
oppositely polarized material 
• A single pn junction has two different types of bias: 
• forward bias 
• reverse bias 
• Thus, a two-pn-junction device has four types of bias. 
Position of the terminals and symbol 
of BJT. 
 
• Base is located at the middle  
   and more thin from the level  
   of collector and emitter 
• The emitter and collector     
   terminals are made of the  
   same type of semiconductor  
   material, while the base of the  
   other type of material 
Page 5


Bipolar Junction Transistor 
(BJT) 
CHAPTER 3 
Introduction 
• The basic of electronic system nowadays is 
 semiconductor device.  
• The famous and commonly use of this device 
is BJTs 
 (Bipolar Junction Transistors). 
• It can be use as amplifier and logic switches. 
• BJT consists of  three terminal: 
 ? collector : C 
 ? base : B 
 ?emitter : E 
• Two types of BJT : pnp and npn 
 
Transistor Construction 
• 3 layer semiconductor device consisting: 
• 2 n- and 1 p-type layers of material ? npn transistor 
• 2 p- and 1 n-type layers of material ?pnp transistor 
• The term bipolar reflects the fact that holes and 
electrons participate in the injection process into the 
oppositely polarized material 
• A single pn junction has two different types of bias: 
• forward bias 
• reverse bias 
• Thus, a two-pn-junction device has four types of bias. 
Position of the terminals and symbol 
of BJT. 
 
• Base is located at the middle  
   and more thin from the level  
   of collector and emitter 
• The emitter and collector     
   terminals are made of the  
   same type of semiconductor  
   material, while the base of the  
   other type of material 
Transistor currents  
-The arrow is always drawn 
  on the emitter 
 
-The arrow always point  
  toward the n-type 
 
-The arrow indicates the  
  direction of the emitter       
  current: 
pnp:E ? B 
npn: B ? E 
I
C
=the collector current 
I
B
= the base current 
I
E
= the emitter current 
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