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Reference Guide

Permachart - Marketing Reference Guide: Semiconductor Device, Precision Rectifier, Envelope Detector

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Fall 2015
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Department
Electrical Engineering
Course Code
4400:307
Professor
All
Chapter
Permachart

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permacharts.com
TM
permacharts
Electronics I
Laplace transform applies only to time functions that are zero
for t< 0; it implicates complex frequency s= jv+ s
Waveforms
Semiconductor Devices
A Fourier series applies to signal waveforms that are periodic
functions of time
• A periodic signal with a complex waveform has a discrete
spectrum of harmonic (sine/cosine) waveforms of magnitudes
determined by Fourier series
A Fourier transform applies to signal waveforms that are
non-periodic functions of time
• A non-periodic waveform has a continuous spectrum of
harmonic components determined by Fourier transform
Diodes are 2-terminal devices that pass current in 1 direction
When a large enough reverse voltage is applied to any diode,
it will conduct current in the reverse direction (breakdown)
Germanium Diodes
Advantage: Forward voltage drop for silicon diodes is about
0.7 V, compared to 0.3 V for germanium diodes
Disadvantage: Breakdown voltages for germanium diodes are
usually less than 100 V, compared to 50–1000 V for silicon
Ideal diode: Diode is either an open circuit or a short circuit
• Diode designed to operate in the breakdown region;
used to establish a fixed DC voltage or limit a
varying signal to a peak voltage
• Constructed to work in the reverse-bias direction
Zener diode is not in breakdown if reverse-bias current is
insufficient; instead, it will act as an open circuit
• A diode that will emit visible or infrared light
when sufficient forward voltage is applied
• When injected, minority carriers in forward-biased
pn junction recombine to release energy
With Si and Ge, energy is released as heat
• With GaAs, energy is released as photon at red, yellow or
green wavelengths (depending on impurities added)
Diodes
• Any two-terminal linear circuit can be replaced by a single
voltage source in series with single resistance (Thevenin
circuit) or current source in parallel with resistor (Norton circuit)
Semiconductor Junctions
N-type: Semiconductor doped with donors (phosphorus, arsenic,
antimony) which have loosely bound electrons
P-type: Semiconductor doped with acceptors (boron, gallium,
indium) which have atoms that leave an electron vacancy (hole)
Hole: The mobile positive charge in semiconductor materials
Doping: The process of adding a controlled amount of a specific
impurity to control a material’s conductivity
Forward bias: Voltage required to turn on a pn junction
Reverse bias: Voltage applied to a pn junction that prevents the
junction from conducting
• In the presence of an electric field,
a hole takes an electron from an
atom of silicon (usual
semiconductor material)
• This event is repeated in a
consistent direction,
resulting in conduction by hole
P-N JUNCTIONS
• An npn transistor consisting of two junctions; a p-type material
is placed between two n-type materials
• Almost all of the electrons injected from the emitter into the
thin base region are collected by the collector
• A doped semiconductor provides a channel for flow of current
from drain D to source S; p-type at the center controls current
• Positive voltage applied to Dcauses IDto flow downwards
(i.e., electrons upwards)
• When negative voltage is applied to G, junction is reverse-biased;
depletion region eliminates conduction electrons from channel
• FET has very small gate current and low voltage gain
BIPOLAR SEMICONDUCTOR
FIELD-EFFECT TRANSISTOR (FET)
iI v
V
gdi
dv
I
V
v
V
gIIV
DDSS GS
P
mD
GS
DSS
P
GS
P
mDDSSP
=−
≡=
=−
()
1
21
2
2
• Biasing the FET means
to select a point on
the curve around
which it will
operate
ZENER DIODE
• Metal semiconductor junction diode
• Has low 0.3 V forward voltage drop
Al or Pt may act as acceptor when in contact with n-type Si
SCHOTTKY DIODE
LIGHT-EMITTING DIODE (LED)
• A diode that produces a current or a voltage in
response to light
• Reverse saturation current depends on generation
of hole-electron pairs by average thermal energy of the crystal
• Current can be increased further by light illumination
PHOTODIODE (LIGHT-SENSITIVE DIODE)
• A diode that acts as a capacitance controlled
by the reverse-bias voltage
• No forward bias due to high shunt conductance
VARACTOR (VARICAP DIODE)
A peak detector is a circuit that hold the peak value of the input
• The capacitor in a peak detector most hold its charge for the duration of
the signal measurement
• If RCproduct is very large, v3equals the highest peaks in v2
• If RCproduct is small enough, v3will be able to follow the envelope of v2
• Peak detector is used in radio receiver as automatic gain control
• Convert to DC power supply by
putting capacitor parallel with RL
Diode bridge: Four diodes connected
as a bridge
circuit to
provide for
full-wave
rectification
FULL-WAVE BRIDGE RECTIFIER
LAPLACE TRANSFORM
• Envelope detector used in AM radio circuits to
recover low frequency audio envelope modulated on
a high frequency carrier
• Rate of change of v
emust satisfy
dv dt
vRC
e
e
1
Clipper: A circuit that
regulates voltage by
eliminating any part of a
signal that is greater in
magnitude than set voltage
Rectification:
Elimination of
positive or
negative portion
of signal
Half-wave rectifier: Uses only one-half of input cycle; negative half of sine wave is lost
Full-wave rectifier: Uses all of input cycle; efficiency increases as all incoming ac is used
Diodes in Circuits
PEAK DETECTOR ENVELOPE DETECTOR
Equivalent Circuits
FOURIER SERIES & FOURIER TRANSFORM
Diode or
metallic rectifier Zener diode Bipolar voltage limiter
(symmetrical zener diode)
AK
Tunnel diode
Pin diode Photodiode
(photosensitive type)
Light emitting
diode (LED)
Temperature
sensitive diode
Trigger diac
(npn)
KA
Trigger diac
(pnp)
AK
Bidirectional
trigger diac (npn)
TT
Bidirectional
trigger diac (pnp)
TT
Phototransistor (npn)
EC
or EC
B
n-type gate
Transistor
(pnp)
EC
B
Transistor
(npn)
EC
B
G
AK
p-type gate
G
AK
Semiconductor controlled rectifiers (SCRs)
Thyristor
bidirectional triode
G
TT
pnp transverse-biased base transistor
or
Darlington-type transistor

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Description
permacharts TM E le c t r o n ic sI Waveforms Diodes Equivalent Circuits • Diodes are 2-terminal devices that pass current in 1 d• Any two-terminal linear circuit can be replaced by a single •When a large enough reverse voltage is applied to any diode,age source in series with single resistance (Thevenin it will conduct current in the reverse direction (breakdown)uit) or current source in parallel with resistor (Norton circuit) Germanium Diodes Advantage: Forward voltage drop for silicon diodes is about 0.7V,compared to 0.3V for germanium diodes Disadvantage: Breakdown voltages for germanium diodes are usually less than 100V,compared to 50–1000V for silicon FOURIER SERIES & FOURIER TRANSFORM Ieal diode: Diode is either an open circuit or a short circuit • A Fourier series applies to signal waveforms that are periodic Semiconductor Junctions functions of time • A periodic signal with a complex waveform has a discrete P-N JUNCTIONS sectrum of harmonic (sine/cosine) waveforms of magnitudes N-type: Semiconductor doped with donors (phosphorus,arsenic, determined by Fourier series antimony) which have loosely bound electrons • A Fourier transform applies to signal waveforms that are P-type: Semiconductor doped with acceptors (boron,gallium, non-periodic functions of time ZENER DIODE indium) which have atoms that leave an electron vacancy (hole) • A non-periodic waveform has a continuous spectrum of Hole: The mobile positive charge in semiconductor materials harmonic components determined by Fourier transform • Diode designed to operate in the breakdown region; Doping: The process of adding a controlled amount of a specific LAPLACE TRANSFORM used to establish a fixed DC voltage or limit a impurity to control a material’s conductivity varying signal to a peak voltage • Laplace transform applies only to time functions that • Constructed to work in the reverse-bias direction Forward bias: Voltage required to turn on a pn junction fr t < 0; it implicates complex frequency s = j + •Zener diode is not in breakdown if reverse-bias current iserse bias: Voltage applied to a pn junction that prevents the junction from conducting insufficient; instead,it will act as an open circuit • In the presence of an electric field, Semiconductor Devices SCHOTTKY DIODE a hole takes an electron from an • Metal semiconductor junction diode atom of silicon (usual A K semiconductor material) • Has low 0.3V forward voltage drop Diode or Zener diodepolar voltage lTunnel diode • Al or Pt may act as acceptor when in contact with n-type Sis event is repeated in a metallic rectifier (symmetrical zener diode) consistent direction, LIGHT-EMITTING DIODE (LED) resulting in conduction by hole • A diode that will emit visible or infrared light when sufficient forward voltage is applied Pin diode(photosensitive diode (LED)nsensitive diode • When injected,minority carriers in forward-biased pn junction recombine to release energy K A A K T T T T •With Si and Ge,energy is released as heat Trigger diac Trigger diac BidirectionaBidirectional • With GaAs,energy is released as photon at red,yellow or (npn) (pnp) trigger diac trigger diac (pnp)green wavelengths (depending on impurities added) m o or E C E C PHOTODIODE (LIGHT-SENSITIVE DIODE) E C E C B B • A diode that produces a current or a voltage in c B Transistor Transistor response to light BIPOLAR SEMICONDUCTOR . Phototransistor (npn) (pnp) (npn) • Reverse saturation current depends on generation • An npn transistor consisting of two junctions; a p-type material G G G of hole-electron pairs by average thermal energy of the crystaled between two n-type materials s A K A K T T t n-type gate p-type gate Thyristor • Current can be increased further by light illumination• Almost all of the electrons injected from the emitter intorthe Semiconductor controlled rectifbidirectional triode VARACTOR (VARICAP DIODE) thin base region are collected by the collector • A diode that acts as a capacitance controlled a or by the reverse-bias voltage h Darling on-type tranpnp transverse-biased base transistorforward bias due to high shunt conductance c a Diodes in Circuits m Clipper: Acircuit that FULL-WAVE BRIDGE RECTIFIER regulates voltage by • Convert to DC power supply by FIELD-EFFECT TRANSISTOR (FET) r eliminating any part of a putting capacitor parallel with R• A doped semiconductor provides a channel for flow of current signal that is greater in L from drain D to source S; p-type at the center controls current magnitude than set voltageDiode bridge: Four diodes connecte• Positive voltage applied to D causes I downwards p Rectification: as a bridge (i.e.,electrons upwards) D Elimination of circuit to positive or provide for • When negative voltage is applied to G,junction is reverse-biased; negative portion full-wave depletion region eliminates conduction electrons from channel of signal rectification • FET has very small gate current and low voltage gain 2 Half-wave rectifier: Uses only one-half of input cycle; negative half of sine wave is lost  vGS Full-wave rectifier: Uses all of input cycle; efficiency increases as all incoming ac is used S SD D= − 1 V   P  PEAK DETECTOR ENVELOPE DETECTOR dD 2DSS  vGS  •A peak detector is a circuit that hold the peak value of the in• Envelope detector used inAM radio circuits to gm ≡ =dv −V 1 − V  • The capacitor in a peak detector most hold its charge for the duration ofw frequency audio envelope modulated on GS P  P  the signal measurement a high frequency carrier I Vg I = − • Rate of change of vt satisfyedt 1 SP S Dm D () • IfCRproduct is very l3rge,v equals the highes2 peaks in v e C v R 〈 • IfCR product is small en3ugh,v will be able to follow t2e envelope of v e • Biasing the FET means • Peak detector is used in radio receiver as automatic gain control to select a point on the curve around which it will operate permacharts TM Transistors Diodes in Circuits • A transistor is a three-terminal semiconductor device that C OMMON EMITTER (cont’d) amplifies electrical signals when in its active state • Most common configuration for • For npn transistor to stay in active staCe, v ≤ v a amplification VOLTAGE REGULATOR When A Zener Diode Is In Shunt With The Load • Has both high voltage and current gain • Voltage gain is greatest when an • Rdd(opping resistor) is chosen at emitter bypass capacitor is used Zmin(necessary to maintaiZ ) , vcc ,and R Lmin L is maximum) • Load voltage vis nearly constant, dnatuWht i C2 3 C , L
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