EDC - BJT

.HISTORY. .Construc�on.
 The BJT is constructed with three doped semiconductor regions
1904 - J.A Fleming separated by two P -N junc�ons.
 Vacuum Tube Diode
 The term bipolar refers to the use of both holes and electrons
AKA Fleming Valve, Thermionic Valve
as current carriers in the transistor structure.
 Thermionic Emission

Base – Emiter (BE) Junc�on

 The PN junc�on joining the base region and the emiter region.

Base – Collector (BC) Junc�on

 The PN junc�on joining the base region and the collector
region.

1906 - Lee de Forest Width: 1. Collector

 Vacuum Tube Triode 2. Emiter
 Added a 3rd element to the vacuum tube 3. Base Base – Width Ra�o(1:150)
called the Control Grid.
Doping: 1. Emiter – Heavily doped
 1st amplifier.
2. Collector
3. Base – lightly doped

Majority Carrier: Electron

 Electrons are faster.

1939 - Russell Ohl

 P-N junc�on

Majority Carrier: Holes

1947 - John Bardeen
- Water Bratain
- William Shockley – Supervisor
 December 23, 1947
 Point Contact Transistor – 1st transistor.

.DUAL DIODE MODEL.

1949 - William Shockley

 Bipolar Junc�on Transistor
Bipolar – 2 carriers (electron and holes)
Junc�on – boundary or interface between two
types of semiconductor materials
Transistor – Transfer Resistor
- it transfers the resistance from one end
of the device to the other end.
 EDC - BJT
.Characteris�c Curve. .Power Dissipa�on.
𝑃𝑃𝐷𝐷 = 𝑉𝑉𝐶𝐶𝐶𝐶 ∙ 𝐼𝐼𝐶𝐶

𝑡𝑡𝑜𝑜𝑜𝑜
𝑃𝑃𝐷𝐷(𝑎𝑎𝑎𝑎𝑎𝑎.) = � � 𝑉𝑉𝐶𝐶𝐶𝐶(𝑠𝑠𝑠𝑠𝑠𝑠) ∙ 𝐼𝐼𝐶𝐶(𝑠𝑠𝑠𝑠𝑠𝑠)
𝑇𝑇

𝑃𝑃𝑂𝑂(𝑎𝑎𝑎𝑎) = 𝑉𝑉𝐶𝐶𝐶𝐶(𝑟𝑟𝑟𝑟𝑟𝑟) 𝐼𝐼𝐶𝐶(𝑟𝑟𝑟𝑟𝑟𝑟)

.Common Configura�on.
𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴
Cutoff Region
 Not-conduc�ng 𝐼𝐼𝐸𝐸 = 𝐼𝐼𝐵𝐵 + 𝐼𝐼𝐶𝐶 𝐼𝐼𝐸𝐸 = 𝐼𝐼𝐵𝐵 + 𝐼𝐼𝐶𝐶 − 𝐼𝐼𝐶𝐶𝐶𝐶𝐶𝐶
 𝐼𝐼𝐶𝐶 = 0
 𝑉𝑉𝐶𝐶𝐶𝐶 ≈ 𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂 → 𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶 𝑰𝑰𝑬𝑬 ≃ 𝑰𝑰𝑪𝑪

Ac�ve Region 𝛽𝛽 =
𝐼𝐼𝐶𝐶
→ 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓, ℎ𝑓𝑓𝑓𝑓
 Conducts at normal opera�on. 𝐼𝐼𝐵𝐵
 0 < 𝐼𝐼𝐶𝐶 < 𝐼𝐼𝑠𝑠𝑠𝑠𝑠𝑠. → 𝑎𝑎𝑎𝑎𝑎𝑎 𝑎𝑎𝑎𝑎 𝑎𝑎 𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 (20 − 200)𝑖𝑖𝑖𝑖 𝑛𝑛𝑛𝑛𝑛𝑛 𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔 𝛽𝛽 = 100
𝐼𝐼𝐶𝐶 𝛽𝛽
𝛼𝛼 = = → 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓
𝐼𝐼𝐸𝐸 𝛽𝛽+1

𝐼𝐼𝐸𝐸
Satura�on Region 𝛾𝛾 =
𝐼𝐼𝐵𝐵
→ 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓
 Reach Max Current (𝐼𝐼𝑠𝑠𝑠𝑠𝑠𝑠. )
 𝐼𝐼𝐶𝐶 = 𝐼𝐼𝑠𝑠𝑠𝑠𝑠𝑠. 𝑰𝑰𝑪𝑪 = 𝜷𝜷𝑰𝑰𝑩𝑩
 𝑉𝑉𝐶𝐶𝐶𝐶 ≈ 𝑆𝑆ℎ𝑜𝑜𝑜𝑜𝑜𝑜 → 𝐴𝐴𝐴𝐴𝐴𝐴 𝑎𝑎𝑎𝑎 𝑎𝑎 𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑺
A BJT is a Current-Controlled Current Source (CCCS)
because a small change in 𝐼𝐼𝐵𝐵 can cause a large change in 𝐼𝐼𝐶𝐶 .

.Mode of Opera�on.
 Deple�on Region Shrink when FB. Common – Common – Common –
 Deple�on Region Widen when RB. Base Collector / Emiter /
Emiter-
𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝐵𝐵 − 𝐸𝐸 𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽 𝐵𝐵 − 𝐶𝐶 𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽𝐽
𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝐹𝐹𝐹𝐹 𝑹𝑹𝑹𝑹 Follower
(Amplifier) Applica�on Boltage Current Everything
𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝐹𝐹𝐹𝐹 𝐹𝐹𝐹𝐹 amplifier/ amplifier/
(ON switch) Isola�on/
𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝑅𝑅𝑅𝑅 𝑹𝑹𝑹𝑹 Z – matching
(OFF switch)
Output 𝐼𝐼𝐶𝐶 𝐼𝐼𝐸𝐸 𝐼𝐼𝐶𝐶
𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑅𝑅𝑅𝑅 𝑭𝑭𝑭𝑭
Input 𝐼𝐼𝐸𝐸 𝐼𝐼𝐵𝐵 𝐼𝐼𝐵𝐵
𝐼𝐼𝑜𝑜𝑜𝑜𝑜𝑜 𝐼𝐼𝐶𝐶 ≃ 𝐼𝐼𝐸𝐸 𝐼𝐼𝐸𝐸 ≫ 𝐼𝐼𝐵𝐵 𝐼𝐼𝐶𝐶 > 𝐼𝐼𝐵𝐵
𝑨𝑨𝒊𝒊 =
𝐼𝐼𝑖𝑖𝑖𝑖 𝐼𝐼𝐶𝐶 𝐼𝐼𝐸𝐸 𝐼𝐼𝐶𝐶
𝛼𝛼 = ≃ 1 𝛾𝛾 = ≫ 1 𝛽𝛽 = > 1
𝐼𝐼𝐸𝐸 𝐼𝐼𝐵𝐵 𝐼𝐼𝐵𝐵
𝐿𝐿𝐿𝐿𝐿𝐿 𝐻𝐻𝐻𝐻𝐻𝐻𝐻𝐻 𝑀𝑀𝑀𝑀𝑀𝑀
.Thermal Runaway. 𝒁𝒁𝒊𝒊𝒊𝒊 𝐿𝐿𝐿𝐿𝐿𝐿 𝐻𝐻𝐻𝐻𝐻𝐻𝐻𝐻 𝑀𝑀𝑀𝑀𝑀𝑀
1 𝑉𝑉𝑜𝑜𝑜𝑜𝑜𝑜 𝑉𝑉𝐶𝐶 ≫ 𝑉𝑉𝐸𝐸 𝑉𝑉𝐵𝐵 ≃ 𝑉𝑉𝐸𝐸 𝑉𝑉𝐶𝐶 > 𝑉𝑉𝐵𝐵
 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 → 𝑁𝑁𝑁𝑁𝑁𝑁 �𝑇𝑇 ∝ � 𝑨𝑨𝒗𝒗 =
𝑅𝑅 𝑉𝑉𝑖𝑖𝑖𝑖 𝑉𝑉𝐶𝐶 𝑉𝑉𝐸𝐸 𝑉𝑉𝐶𝐶
𝐴𝐴𝑣𝑣 = ≫1 𝐴𝐴𝑣𝑣 = ≃1 𝐴𝐴𝑣𝑣 = >1
𝑉𝑉𝐸𝐸 𝑉𝑉𝐵𝐵 𝑉𝑉𝐵𝐵
𝐻𝐻𝐻𝐻𝐻𝐻𝐻𝐻 𝐿𝐿𝐿𝐿𝐿𝐿 𝑀𝑀𝑀𝑀𝑀𝑀
𝒁𝒁𝒐𝒐𝒐𝒐𝒐𝒐 𝐻𝐻𝐻𝐻𝐻𝐻𝐻𝐻 𝐿𝐿𝐿𝐿𝐿𝐿 𝑀𝑀𝑀𝑀𝑀𝑀
𝑨𝑨𝑷𝑷 = 𝐴𝐴𝑣𝑣 ∙ 𝐴𝐴𝑖𝑖 𝑀𝑀𝑀𝑀𝑀𝑀 𝑀𝑀𝑀𝑀𝑀𝑀 𝐻𝐻𝐻𝐻𝐻𝐻𝐻𝐻
𝑃𝑃ℎ𝑎𝑎𝑎𝑎𝑎𝑎 𝑆𝑆ℎ𝑖𝑖𝑖𝑖𝑖𝑖 𝑁𝑁/𝐴𝐴 𝑁𝑁/𝐴𝐴 180°
 EDC - BJT
.AC Analysis.
Equivalent Circuit Frequency Response
Low Frequency Analysis
Cutoff-Frequency (𝒇𝒇𝑳𝑳 ) @𝑋𝑋𝐶𝐶 = 𝑅𝑅
1
𝑋𝑋𝐶𝐶 = 𝑅𝑅 =
2𝜋𝜋𝜋𝜋𝜋𝜋
1
𝑓𝑓𝐿𝐿 =
2𝜋𝜋𝜋𝜋𝜋𝜋

High Frequency Analysis

1
𝑓𝑓𝐻𝐻 =
2𝜋𝜋𝑅𝑅𝑇𝑇ℎ 𝐶𝐶

Miller Effect Capacitance

∆𝑉𝑉𝐶𝐶𝐶𝐶
𝑟𝑟𝑜𝑜 = ≈ ∞ ≈ 𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐
∆𝐼𝐼𝐶𝐶
→ 𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢 𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖

26𝑚𝑚𝑚𝑚
𝑟𝑟𝑒𝑒 =
𝐼𝐼𝐸𝐸

𝑉𝑉𝑏𝑏 = 𝐼𝐼𝑒𝑒 (𝑟𝑟𝑒𝑒 + 𝑅𝑅𝐸𝐸 )

𝐶𝐶𝑀𝑀𝑀𝑀 = (1 − 𝐴𝐴𝑣𝑣 )𝐶𝐶𝑓𝑓
𝑍𝑍𝑖𝑖𝑖𝑖 = 𝐵𝐵𝑎𝑎𝑎𝑎 (𝑟𝑟𝑒𝑒 + 𝑅𝑅𝐸𝐸 )
1
𝐶𝐶𝑀𝑀𝑀𝑀 = �1 − � 𝐶𝐶 ≈ 𝐶𝐶𝑓𝑓
𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 → 𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝐴𝐴𝑣𝑣 𝑓𝑓
 EDC - BJT
.Basic Configura�ons.
EDC - BJT
EDC - BJT
EDC - BJT