ME 4447: Mechatronics Transistors

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ME 4447 MechatronicsTransistors

• Paxton Billingsley
• Faiza Hassan
• Hanif Hunter
• David Stone

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Definition

• A transistor is an electronic three terminal
  device, consisting of a collector, base and
  emitter.

C
B
E
E
3
Transistor Properties

• One-way property
• signal gain
• coupling of circuits with differing impedance
  levels
• switch (as in ME 4447)
• non-linear effects used in communication circuits

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Transistor Types

• Bipolar junction transistors
• -npn
• -pnp

• FETS
• -JFETS
• -MOSFETS

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Bipolar Junction Transistors (BJT)

• Invented in 1948 by Bill Shockley at Bell
  Laboratories to amplify telephone signals
• First practical design to replace vacuum tubes
• Constructed as a sandwich of semiconductors
  doped with N-type and P-type impurities

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Two Types of BJTs

• NPN BJT

• PNP BJT

C
E
E
C
N-type
P-type
B
B
B
B
P-type
N-type
C
E
N-type
P-type
E
C
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How They Work

• Holes flow from (1) to (2)
• Forward bias voltage controls the collector
  current
• IC is independent of VBE

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Summary of BJT Operation

• N-type electrons are majority carriers
• P-type holes are majority carriers
• Majority carriers always flow from emitter to
  collector
• Increasing base-emitter voltage increases current
  flow from emitter to collector

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Common Emitter

• Emitter is common to input and output
• Most commonly used configuration
• Medium input and output impedance
• High voltage gain
• High current gain

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Common Base

• Base is common to input and output
• Used in high frequency applications

• Low input impedance
• High output impedance
• Unity current gain
• High voltage gain

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Common Collector

• More commonly known as emitter follower
• Used as a buffer for circuits with different
  impedences
• High input impedence, low output impedence
• Unity current gain, high voltage gain

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Summary of BJT Configurations
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Field Effect Transistors(Paxton Billingsley)
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History

• Invented in late 1940s by Shockley.
• Late 1960s manufacturing enabled effective use
  of field-effect transistors.
• Shockley never prospered in Silicon Valley.

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Field Effect Operations

• Control one electrical signal with another.
• 3 - connections, gate, source and drain.
• Transfer patterns of signal fluctuation from a
  small input signal to larger output.

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Why is it called Field Effect?

• Because of the Field Effect!
• Strong electrical field created .
• This field controls a second signal.
• The second signal mimics the gate signal but
  larger.

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Polarity

• 2 types
• n-channel corresponds to npn
• p-channel corresponds to pnp
• Behave similarly except in p-type hole not
  electrons cause the current.

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Variety

• 2 varieties of FET
• junction FET (JFET)
• metal-oxide semiconductor (MOSFET)
• similar properties

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Junction FET (JFET)
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Basic JFET
Drain

iG
iD
Gate
VDS

-
VGS
-
Source
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JFET Terminals

• 3 Terminals
• Gate (G) this is the input signal with
  information
• Source (S) this is the source voltage
• Drain (D) this is the output

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JFET Characteristics
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JFET Regions of Operation

• Ohmic Region Behaves as a resistor. Gate
  Voltage controls level of resistance, starting
  linear then moving non-linear as VD increases.
• Saturation Region Device behaves as a current
  source controlled by gate source voltage.

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FET Applications

• Preferred for weak-signal work, for example in
  wireless communications and broadcast receivers.
• Not used for high-power amplification.
• Single chip may contain many thousands of FETs
  along with other components.

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Mosfet
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Power Transistors

• Used for power amplification.
• They can be BJTs and MOSFETs or any other type of
  transistor.
• Power transistor is just an application of any
  transistor

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Uses

• Audio Amplification
• Amplification in a RF (radio frequency) systems
• Many more uses

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Some points

• Common-means that that part is grounded and is
  not the input nor the output signal.
• AV is the voltage gain.
• AI is the current gain.
• AP is the power gain and the product of AV and
  AI.
• Whenever there is a thevinin voltage that part of
  the circuit was thevinised. To change back we
  multiply by vth/vo.
• Transconductance of BJTs is gm. This number is
  constant for given BJTs.

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3 Types Bipolar Power Transistor Setups or 3 ways
a BJT is hooked up in a circuit

• Common Emitter (CE)
• Common Base (CB)
• Common Collector (CC)

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Bipolar Power Transistor CE

• AVth-gmRLvth/vo
• For R5 0, otherwise
• AVth-RL/R5vth/vo
• AI-?o
• AP Avthvin/vth AI

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Bipolar Power Transistor CC

• AVth1vth/vo
• AI?o1
• AP Avthvin/vth AI
• ?o1

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Bipolar Power Transistor CB

• AVthgmRLvth/vo
• AI1
• AP Avthvin/vth AI
• gmRLvth/vo

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3 Types FET Power Transistor Setups or 3 ways a
FET is hooked up in a circuit

• Common Source (CS)
• Common Drain (CD)
• Common Gate (CG)

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FET Power Transistor CS

• AVthgmRLvth/vo
• For R5 0, otherwise
• AVth-RL/R5vth/vo
• AI ?
• AP ?

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FET Power Transistor CD

• AVth1vth/vo
• AI ?
• AP ?

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FET Power Transistor CG

• AVthgmRLvth/vo
• AI 1
• AP gm vin/vth RL

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Power Transistors

• Used for power amplification.
• They can be BJTs and MOSFETs or any other type of
  transistor.
• Power transistor is just an application of any
  transistor

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Uses

• Audio Amplification
• Amplification in a RF (radio frequency) systems
• Many more uses

39
Some points

• Common-means that that part is grounded and is
  not the input nor the output signal.
• AV is the voltage gain.
• AI is the current gain.
• AP is the power gain and the product of AV and
  AI.
• Whenever there is a thevinin voltage that part of
  the circuit was thevinised. To change back we
  multiply by vth/vo.
• Transconductance of BJTs is gm. This number is
  constant for given BJTs.

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3 Types Bipolar Power Transistor Setups or 3 ways
a BJT is hooked up in a circuit

• Common Emitter (CE)
• Common Base (CB)
• Common Collector (CC)

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Bipolar Power Transistor CE

• AVth-gmRLvth/vo
• For R5 0, otherwise
• AVth-RL/R5vth/vo
• AI-?o
• AP Avthvin/vth AI

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Bipolar Power Transistor CC

• AVth1vth/vo
• AI?o1
• AP Avthvin/vth AI
• ?o1

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Bipolar Power Transistor CB

• AVthgmRLvth/vo
• AI1
• AP Avthvin/vth AI
• gmRLvth/vo

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3 Types FET Power Transistor Setups or 3 ways a
FET is hooked up in a circuit

• Common Source (CS)
• Common Drain (CD)
• Common Gate (CG)

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FET Power Transistor CS

• AVthgmRLvth/vo
• For R5 0, otherwise
• AVth-RL/R5vth/vo
• AI ?
• AP ?

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FET Power Transistor CD

• AVth1vth/vo
• AI ?
• AP ?

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FET Power Transistor CG

• AVthgmRLvth/vo
• AI 1
• AP gm vin/vth RL

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Conclusion

• Most common applications of transistors
• switch
• amplifier

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QUESTIONS