The document discusses several power semiconductor devices: 1. A Silicon Controlled Rectifier (SCR) is a solid state device that controls current flow through its four layers when a gate signal exceeds a threshold. 2. A Bipolar Junction Transistor (BJT) is composed of three terminals - collector, base, and emitter. There are two types, npn and pnp, which differ in their layer doping. 3. A Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) uses a metal gate separated from a semiconductor channel by an oxide layer to control current flow between its source and drain based on the gate voltage. N-channel and

3. Silicon Controlled Rectifier
• A Silicon Controlled Rectifier (or Semiconductor Controlled
Rectifier) is a four layer solid state device that controls current
flow
• The name “silicon controlled rectifier” is a trade name for the
type of thyristor commercialized at General Electric in 1957
• An SCR can be seen as a conventional rectifier controlled by a
gate signal
• It is a 4-layered 3-terminal device
• When the gate to cathode voltage exceeds a certain threshold,
the device turns 'on' and conducts current

4. V-I Characteristic Curve

5. • 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

6. 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 nE
B
C p n pE
B
C
Cross Section Cross Section
B
C
E
Schematic
Symbol
B
C
E
Schematic
Symbol
• Collector doping is usually ~ 109
• Base doping is slightly higher ~ 1010 – 1011
• Emitter doping is much higher ~ 1017

7. Various Regions (Modes) of Operation of BJT
• Most important mode of operation
• Central to amplifier operation
• The region where current curves are practically flat
Active:
Saturation: • Barrier potential of the junctions cancel each other out causing a
virtual short (behaves as on state Switch)
Cutoff: • Current reduced to zero
• Ideal transistor behaves like an open switch
* Note: There is also a mode of operation called inverse
active mode, but it is rarely used.

8. 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

9. Metal Oxide Semiconductor Field
Effect Transistor
 A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a
semiconductor device.
 A MOSFET is most commonly used in the field of power electronics.
 A semiconductor is made of manufactured material that acts
neither like a insulator nor a conductor.

10. Schematic structure of MOSFET

11. Working principle of MOSFET
 A metal–oxide–semiconductor field-effect transistor (MOSFET) is based on the
modulation of charge concentration by a MOS capacitance between a body electrode
and a gate electrode located above the body and insulated from all other device regions by
a gate dielectric layer which in the case of a MOSFET is an oxide, such as silicon dioxide.
 If dielectrics other than an oxide such as silicon dioxide (often referred to as oxide) are
employed the device may be referred to as a metal–insulator–semiconductor FET
(MISFET).
 Compared to the MOS capacitor, the MOSFET includes two additional terminals
(source and drain), each connected to individual highly doped regions that are
separated by the body region

12. N and P channel of MOSFET
 If the MOSFET is an n-channel or nMOS FET,
then the source and drain are 'n+' regions and
the body is a 'p' region.
 If the MOSFET is a p-channel or pMOS FET,
then the source and drain are 'p+' regions and
the body is a 'n' region.

13. ECE 442 Power Electronics 13
IGBT: Insulated-Gate Bipolar Transistor
• Combination BJT and MOSFET
– High Input Impedance (MOSFET)
– Low On-state Conduction Losses (BJT)
• High Voltage and Current Ratings
• Symbol

14. Cross-section Of IGBT
• Cell structure similar to power MOSFET cell.
• P-region at collector end unique feature of IGBT compared to MOSFET.
• Punch-through (PT) IGBT - N+ buffer layer present.
• Non-punch-through (NPT) IGBT - N+ buffer layer absent.
14

15. IGBT On-state Operation
15
•Vgs>Vth , Channel is shorting Body-Drain-Drift regions.
•P+ inject holes in to N+ region
•Holes moves towards body region along a random path .
•Many holes will attracted by emitter metallization.
•Some holes recombines with electrons.

16. collector
emitter
gate
gate
drain
source
IGBT I-V Characteristics and Circuit Symbols
• Transfer curve
• Output characteristics
• N-channel IGBT circuit symbols
16
Vth

17. Lighting dimmers
Snubber circuits
Hvdc electricity transmission
Circuit breakers
Television
Ac and dc motor drives
High ,medium ,low power Applications