Transistors
Content
NAIT 2000
The Use of Transistor Technology in Manufacturing Thomas E. Scott, Ph.D. Ohio University
For your own personal copy of this presentation www.ent.ohiou.edu/~tscott
Solid State Switching
January 3, 2000
EXTRA!!! EXTRA!!
EMR is DEAD
As the 21st century commences, we bid fond adieu to one of the mainstays of industrial electronics, the electro-magnetic relay. Surviving are numerous antiquated installations where EMRs continue to…..
Industrial Electronics
• Typical Applications
• • • • • Rectification Motor Control Amplification Regulation Process Control
Transistor
• Capable of performing
• Amplifying • Switching
• Most common types
• Bipolar junction (BJT) • Field effect (FET)
Transistor
• A three terminal device that controls current through the device depending on the amount of voltage applied to the base • PNP or NPN • emitter, base, collector • bipolar device - both holes and electrons are used as internal carriers for maintaining current flow
Transistor
Biasing a Transistor
• Base/emitter junction must be forward biased
• emitter more negative than the base
• base/collector junction must be reverse biased
• base is more negative that the collector
Biasing a Transistor
Transistor Current Flow
• Forward bias of base/emitter causes emitter to inject electrons into the depletion region between the emiitter and the base • Biasing process is the “turn on” action
Transistor Current Flow
Transistor Applications
• Developed to replace mechanical switches
• No moving parts • High resistance when transistor not turned on • Low resistance when transistor turned on
Transistor Applications
Transistor Applications
• May be used as amplifiers
• Transistors gradually shut off • By carefully controlling the base/emitter junction bias, possible to control varying degrees the through put of the emitter/collector current • Acts as an amplifier
Transistors as amplifiers
• Darlington amplifier • Two transistors used together • Gain is multiplicative
Field Effect Transistor
• Like Bipolar Junction transistor except
• BJT is current controlled • FET is voltage controlled
• Two types
• JFETs – Junction FETs • MOSFETs – Metal Oxide Semiconductor FETs • Power MOSFETS have high power capability
Insulated Gate Bipolar
• Has attractive features of both MOSFET and BJT • Very fast on/off times (1 micro second) • Extensively used in
• Inverters • High frequency welding systems
IGBT Application
Special Types of Transistors
• THYRISTOR
• SCR • DIAC • TRIAC
• UJT
THYRISTOR
• Thyra (Greek) - door, inferring either open or closed • Thyristor - generic name for a type of semiconductor switch
• • • • Two stable states - ON and OFF No intermediate state Like a mechanical toggle switch Made up of alternating layers of semiconductor material
THYRISTOR Applications
• Used in lamp-dimming circuits, motor speed control, ignition systems, charging circuits • Control the transfer of power to various AC loads • SCRs, TRIACs, DIACs, and UJTs
Silicon Controlled Rectifier (SCR)
• Major element of motor control equipment • Ratings as high as 2500 Volts and 2500 Amps • Reverse blocking triode thyristor
SCR - Continued
• Three terminals
• anode - P-layer • cathode - N-layer (opposite end) • gate - P-layer near the cathode
• Three junctions - four layers
Connect power such that the anode is positive with respect to the cathode - no current will flow NOTE: Blocked by the reverse bias of junction 2
SCR - Continued
• Positive potential applied to the gate
• Current will flow - TURNED-ON • Once turned on, gate potential can be removed and the SCR still conducts
CALLED LATCHING • Holding current maintains latch
Silicon Controlled Rectifier
SCR - Continued
• Phase controller produces a trigger pulse to permit on a portion of the positive half cycle to get through • Average power delivered is thereby controlled
Silicon Controlled Rectifier
Silicon Controlled Rectifier
SCR Application
• Gate Turn Off switch (GTO) • Electronic (pointless) automotive ignition
TRIAC
• Bidirectional triode thyristor • Equivalent of two SCRs connected • Allows gate control of current flow in either direction
TRIAC Operation
DIAC
• Bi-directional device without a gate • Conducts in both directions but waits for a breakover voltage • Therefore, always the same and not controllable • Acts like two zener diodes in series, but conducts in both directions • Excellent for controlling TRIAC
DIAC - Application
Brightness of a lamp
DIAC - Application
• Brightness of a lamp
• • • • • beginning half cycle, TRIAC off capacitor charges based on RC time constant eventually DIAC is activated TRIAC is activated and conducts Process repeated for each half cycle of the AC sine wave • Adjust the brightness by changing the variable resistance which effects charging time
Unijunction Transistor (UJT)
• Simple two layer transistor • Operates using the principle of avalanche breakdown producing a saw tooth output • Used to trigger an SCR or TRIAC • Also used within pulse circuitry • Output from photocells, thermistors, and other transducers can be used to trigger
Unijunction Transistor (UJT)
UJT as a trigger for an SCR
Industrial Blending Process
• Computer sends bit (5 VDC) to UJT • UJT sends trigger signal to SCR • SCR activates and provides power to device
Application with UJT and SCR
Application with UJT and SCR
Inverter AC Motor Control
Solid State Switching
• Advantages
• No moving parts • Controllable in the time domain
• Disadvantages
• Low resistance - but substantial heat
Solid State Switching
Advice for the future If you own stock in a company who’s main product line is EMRs
SELL!
The Use of Transistor Technology in Manufacturing Thomas E. Scott, Ph.D. Ohio University
For your own personal copy of this presentation www.ent.ohiou.edu/~tscott
Solid State Switching
January 3, 2000
EXTRA!!! EXTRA!!
EMR is DEAD
As the 21st century commences, we bid fond adieu to one of the mainstays of industrial electronics, the electro-magnetic relay. Surviving are numerous antiquated installations where EMRs continue to…..
Industrial Electronics
• Typical Applications
• • • • • Rectification Motor Control Amplification Regulation Process Control
Transistor
• Capable of performing
• Amplifying • Switching
• Most common types
• Bipolar junction (BJT) • Field effect (FET)
Transistor
• A three terminal device that controls current through the device depending on the amount of voltage applied to the base • PNP or NPN • emitter, base, collector • bipolar device - both holes and electrons are used as internal carriers for maintaining current flow
Transistor
Biasing a Transistor
• Base/emitter junction must be forward biased
• emitter more negative than the base
• base/collector junction must be reverse biased
• base is more negative that the collector
Biasing a Transistor
Transistor Current Flow
• Forward bias of base/emitter causes emitter to inject electrons into the depletion region between the emiitter and the base • Biasing process is the “turn on” action
Transistor Current Flow
Transistor Applications
• Developed to replace mechanical switches
• No moving parts • High resistance when transistor not turned on • Low resistance when transistor turned on
Transistor Applications
Transistor Applications
• May be used as amplifiers
• Transistors gradually shut off • By carefully controlling the base/emitter junction bias, possible to control varying degrees the through put of the emitter/collector current • Acts as an amplifier
Transistors as amplifiers
• Darlington amplifier • Two transistors used together • Gain is multiplicative
Field Effect Transistor
• Like Bipolar Junction transistor except
• BJT is current controlled • FET is voltage controlled
• Two types
• JFETs – Junction FETs • MOSFETs – Metal Oxide Semiconductor FETs • Power MOSFETS have high power capability
Insulated Gate Bipolar
• Has attractive features of both MOSFET and BJT • Very fast on/off times (1 micro second) • Extensively used in
• Inverters • High frequency welding systems
IGBT Application
Special Types of Transistors
• THYRISTOR
• SCR • DIAC • TRIAC
• UJT
THYRISTOR
• Thyra (Greek) - door, inferring either open or closed • Thyristor - generic name for a type of semiconductor switch
• • • • Two stable states - ON and OFF No intermediate state Like a mechanical toggle switch Made up of alternating layers of semiconductor material
THYRISTOR Applications
• Used in lamp-dimming circuits, motor speed control, ignition systems, charging circuits • Control the transfer of power to various AC loads • SCRs, TRIACs, DIACs, and UJTs
Silicon Controlled Rectifier (SCR)
• Major element of motor control equipment • Ratings as high as 2500 Volts and 2500 Amps • Reverse blocking triode thyristor
SCR - Continued
• Three terminals
• anode - P-layer • cathode - N-layer (opposite end) • gate - P-layer near the cathode
• Three junctions - four layers
Connect power such that the anode is positive with respect to the cathode - no current will flow NOTE: Blocked by the reverse bias of junction 2
SCR - Continued
• Positive potential applied to the gate
• Current will flow - TURNED-ON • Once turned on, gate potential can be removed and the SCR still conducts
CALLED LATCHING • Holding current maintains latch
Silicon Controlled Rectifier
SCR - Continued
• Phase controller produces a trigger pulse to permit on a portion of the positive half cycle to get through • Average power delivered is thereby controlled
Silicon Controlled Rectifier
Silicon Controlled Rectifier
SCR Application
• Gate Turn Off switch (GTO) • Electronic (pointless) automotive ignition
TRIAC
• Bidirectional triode thyristor • Equivalent of two SCRs connected • Allows gate control of current flow in either direction
TRIAC Operation
DIAC
• Bi-directional device without a gate • Conducts in both directions but waits for a breakover voltage • Therefore, always the same and not controllable • Acts like two zener diodes in series, but conducts in both directions • Excellent for controlling TRIAC
DIAC - Application
Brightness of a lamp
DIAC - Application
• Brightness of a lamp
• • • • • beginning half cycle, TRIAC off capacitor charges based on RC time constant eventually DIAC is activated TRIAC is activated and conducts Process repeated for each half cycle of the AC sine wave • Adjust the brightness by changing the variable resistance which effects charging time
Unijunction Transistor (UJT)
• Simple two layer transistor • Operates using the principle of avalanche breakdown producing a saw tooth output • Used to trigger an SCR or TRIAC • Also used within pulse circuitry • Output from photocells, thermistors, and other transducers can be used to trigger
Unijunction Transistor (UJT)
UJT as a trigger for an SCR
Industrial Blending Process
• Computer sends bit (5 VDC) to UJT • UJT sends trigger signal to SCR • SCR activates and provides power to device
Application with UJT and SCR
Application with UJT and SCR
Inverter AC Motor Control
Solid State Switching
• Advantages
• No moving parts • Controllable in the time domain
• Disadvantages
• Low resistance - but substantial heat
Solid State Switching
Advice for the future If you own stock in a company who’s main product line is EMRs
SELL!
