This document provides an overview of transistors, including their history, types, properties, and applications. It discusses bipolar junction transistors (BJT), junction field-effect transistors (JFET), and metal-oxide-semiconductor field-effect transistors (MOSFET). For each transistor type, the document describes their basic structure and operating principles, as well as examples of their usage in circuits like amplifiers and switches. The key differences between each transistor type are also highlighted.

1. Justin Chow
Jacob Huang
Daniel Soledad
ME 4447/6405
Student Lecture

2.  History
 Properties
 Types
 BJT
 JFET
 MOSFET
 Applications
Overview
Daniel Soledad

3.  Transistor History
 “Transistor” is combination of “transconductance”
and “variable resistor”
 HowTransistors Are Made
▪ Vacuum tubes
▪ Inefficient, fragile, bulky, generated a lot of heat
▪ FirstTransistors
▪ Semiconductors – Bell Labs 1947
Introduction

4.  Packaging
 Surface Mount orThrough Hole
 Usually 3 or 4 terminal device
▪ Can be packaged into ICs
 GeneralApplications
 Amplification/Regulation
 Switches
Introduction

5.  Current Controlled
 i.e: BJT
 The output current is proportional to input current
 Voltage Controlled
 i.e.: JFET, MOSFET
 The output current is proportional to input
voltage

6.  Bipolar JunctionTransistor
 3 semiconductor layers sandwiched together
 Comes in two flavors
NPN BJT PNP BJT
BJT Transistor
Justin Chow

7.  Diodes
Forward Biased Reverse Biased
current flows no current flows
whenVPN > .6-.7V
BJT Transistor

8.  BJT Basics (NPN)
 BE Forward Biased
 BC Reversed Biased
 β=IB / Ic ≈ 100
 IE = IB + IC
BJT Transistor
emitter base collector
Electron Flow

9.  Things to remember
 PNP, biasing opposite
 Conventional current vs electron flow
 A small input current controls a much larger
output current.
BJT Transistor

10.  Operating Regions
BJT Transistor
Operating Region Parameters
Cut Off
VBE <0.7V
IB = IC = 0
Linear
VBE >0.7V
IC = β*IB
Saturated
IB > 0, IC > 0
VBE >0.7V,
VCE 0.2V

11.  Operating Regions
BJT Transistor

12.  From
3rd Exercise
 Turns on/off
coils digitally

13.  Common EmitterAmplifier
BJT Transistor
β=100

14.  Common EmitterAmplifier
BJT Transistor
IB = (Vin − VB) / 10000Ω = (Vin − 0.7) / 10000Ω
IC = β(Vin − 0.7) / 10000Ω
Vout=10000*(Vin-0.7)/1000
When VCE = 0.2V
IC = 9.8 / 1000Ω = 9.8mA
IB = IC / β = 0.098mA
Vin − 0.7 = (0.098mA)(10000Ω)
Vin = 1.68V or greater.

15.  Power Dissipation
 PBJT =VCE * iCE
 Should be below the rated transistor power
 Important for heat dissipation as well
BJT Transistor

16.  Increased Gain
 β = β1 * β2
 VBE =VBE1 +VBE2
 Slower Switching
 2N6282

17.  Analogous to BJT
Transistors
 Output is controlled
by input voltage
rather than by current
 4 Pins vs. 3
BJT FET
Collector Drain
Base Gate
Emitter Source
N/A Body

18.  FET (Field EffectTransistors)
 MOSFET (Metal-Oxide-Semiconductor Field-Effect
Transistor)
 JFET (Junction Field-EffectTransistor)
 MESFET
 HEMT
 MODFET
 Most common are the n-channel MOSFET or JFET
Jacob Huang

19.  In practice the body and
source leads are almost
always connected
 Most packages have these
leads already connected
B
S
G
D
B
S
G
D
S
G
D
MOSFET
JFET

20.  Metal-Oxide Semiconductor F.E.T.
 A.K.A. Insulated-Gate FET (IGFET)
 2 Modes: Enhancement/Depletion

21.  N-Channel
 +Vgs -> More electrons -> More Current
 - Vgs -> Less electrons -> Less current
 P-Channel – Reversed
 Different from BJT

22. Current
flow
B
S
G
D

23.  N-Channel
 VGS >Vth ->Turns on device
 VGS <VTH -> No Current
 P-Channel
 Reversed
 Only E-type used now

24. Region Criteria Effect on Current
Cut-off VGS < Vth IDS=0
Linear VGS > Vth
And
VDS <VGS-Vth
Transistor acts like a
variable resistor,
controlled by Vgs
Saturation VGS > Vth
And
VDS >VGS-Vth
Essentially constant
current
Current
flow
B
S
G
D

25. Current
flow
B
S
G
D

26.  Used in high-power applications
 Heat Sink
 Vertical layout
 Not Planar like other transistors

27.  Reverse BiasVGS => Reduces channel size =>
Reduced Current
 Defaults “on”

28.  Vgs = 0 “on”
 |Vgs|> |Vp| “off”
Vp = Pinch-off or Cut-offVoltage

29.  Internal Capacitance
 Bi-directional
 Cut-off voltage is varying for each JFET
 0.3V – 10V
 N-Channel – NegativeVGS
 P-Channel – PositiveVGS
 Do not Forward Bias JFET – burn out

31. Property BJT MOSFET JFET
Gm Best Worst Medium
Speed High Medium Low
Noise Moderate Worst Best
Good
Switch
No Yes Yes
High-Z Gate No Yes Yes
ESD
Sensitivity
Less More Less

32.  Complementary MOS
 Used in Logic Gates
 P-channel (PMOS) to high
 N-channel (NMOS) to low
 HIGH usually +5V
 LOW usually ground
 Q is high when A = 0, Q is low when A = 1

33. References
Spring 2007/2008 Slides
http://www.made-in-china.com/image/2f0j00ZhaTKREnIQkfM/IC-Transistor.jpg
http://en.wikipedia.org/wiki/JFET
http://en.wikipedia.org/wiki/MOSFET
http://en.wikipedia.org/wiki/Bipolar_junction_transistor
http://www.allaboutcircuits.com/vol_3/chpt_2/8.html
http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/images/basic-
bjt.gif&imgrefurl=http://www.mcmanis.com/chuck/robotics/tutorial/h-
bridge/bjt_theory.html
http://www.allaboutcircuits.com/vol_3/chpt_2/6.html
http://web.engr.oregonstate.edu/~traylor/ece112/lectures/bjt_reg_of_op.pdf
http://hades.mech.northwestern.edu/wiki/index.php/Diodes_and_Transistors#Com
mon_Emitter_Amplifier_Circuit
http://en.wikipedia.org/wiki/Darlington_transistor
http://www.allaboutcircuits.com/vol_3/chpt_6/2.html
http://www.allaboutcircuits.com/vol_3/chpt_4/2.html
http://www.designers-guide.org/Forum/YaBB.pl?num=1162476437/4
http://en.wikipedia.org/wiki/CMOS