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    Dang Nguyen ChauHo Chi Minh City University of TechnologyEmail: [email protected]

    Diodes

    Chapter 2

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    Faculty of EEE Electronic Circuit, 20132

    What is a Diodes?

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    What is a Diodes?

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    Diodes Mode of operation

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    Terminal Charac. Of Junc. Diodes (1)

    The characteristics of curve consists of 3 distinct regions:

    The forward-bias region, determined by v > 0

    The reserve-bias region, determined byVZK< v < 0

    The breakdown region, determined by v < VZK

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    Terminal Charac. Of Junc. Diodes (2)

    The forward-bias region, determined by v > 0

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    Terminal Charac. Of Junc. Diodes (3)

    The forward-bias region, determined by v > 0

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    Terminal Charac. Of Junc. Diodes (4)

    The reserve-bias region, determined byVZK

    < v < 0

    The breakdown region, determined by v < VZK

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    Modeling The Diode Forward Charac.

    3 model of diode characteristic:

    Ideal diode model

    Constant voltage drop model

    The exponential model

    Small signal model

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    Ideal Diodes

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    Ideal Diodes (1)

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    Ideal Diodes

    Example: Assuming the diode to be ideal, find the fraction of each

    cycle during which the diode conducts and the peak value of the diode

    current.

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    Application: The rectifier (1)

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    Electronic Circuit, 201320

    Constant-Voltage-Drop Model (1)

    Example: Assuming the diode to constant-drop-voltage. Find the

    value of output. Sketch output voltage and input-output voltage

    relation.

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    Constant-Voltage-Drop Model (2)

    Example: Calculate the output voltage and current.

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    Exponential Model

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    Exponential Model Graphical Analysis

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    Exponential Model Graphical Analysis

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    Exponential Model Linear Model

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    Notation

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    Small signal Model

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    Small signal Model

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    Faculty of EEE

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    Small signal Model

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    Small signal Model

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    Small signal Analysis

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    Small signal Analysis

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    Small signal Analysis

    Step 1: Eliminate AC sources, find the DC solution (ID,VD) of the

    circuit (use Constant-Voltage-Drop model, unless specified

    otherwise).

    Step 2: Calculate Small-Signal parameters (rd).

    Step 3: Eliminate DC sources, replace the diode with its Small-

    Signal equivalent model and find the Small-Signal solution. Verify the

    assumptions (vd

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    Small signal Analysis

    Example:

    Find output voltage?

    ( ) 5 0.2 sinSv t t

    2n

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    Small signal Analysis

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    Faculty of EEE

    Electronic Circuit, 201343

    Small signal Analysis

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    Small signal Analysis

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    Summary

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    Zener Diode

    Zener diode is a silicon semiconductor device used especially as a

    voltage regulator

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    Example: The Zener diode has a constant reverse breakdown voltage

    VZ = 8.2 V for 75mA iZ 1A. Find R so that VL= VZ is

    maintained at 8.2 V while Vi varies by 10% from its nominal value

    of 12 V.

    Zener Diode

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    Application: Rectifier Circuit

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    Application: Rectifier Circuit

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    Transformer

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    Rectifier Circuit

    Basic rectifier converts an AC voltage to a pulsating DC voltage.

    A filter then eliminates AC components of the waveform to

    produce a nearly constant dc voltage output.

    Rectifier circuits are used in virtually all electronic devices to

    convert the 120 V - 60 Hz AC power line source to the DC voltages

    required for operation of the electronic device.

    In rectifier circuits, the diode state changes with time and a given

    piecewise linear model is valid only for a certain time interval.

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    Rectifier Circuit

    Half-wave rectifier

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    Rectifier Circuit

    Half-wave rectifier

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    Rectifier Circuit

    Half-wave rectifier

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    Rectifier Circuit

    Half-wave rectifier

    Important parameter for design:

    Current-handling capability required of the diode, determined

    by the largest current the diode expected to conduct.

    Peak inverse voltage (PIV): the maximum inverse voltage that

    the diode must be able to withstand without breakdown,

    determined by the largest reverse voltage that is expected to

    appear across the diode.

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    Rectifier Circuit

    Full-wave center-tap rectifier

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    Rectifier Circuit

    Full-wave center-tap rectifier

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    Rectifier Circuit

    Full-wave center-tap rectifier

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    Rectifier Circuit

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    Rectifier Circuit

    Full-wave bridge rectifier

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    R ifi Ci i

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    Rectifier Circuit

    Full-wave bridge rectifier

    Fil

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    Filter

    R tifi Ci it

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    Rectifier Circuit

    R tifi Ci it

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    Rectifier Circuit

    A li ti Cli (li it ) i it

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    Application: Clipper (limiter) circuit

    A li ti Cli (li it ) i it

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    Application: Clipper (limiter) circuit

    A li ti Cli (li it ) i it

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    Application: Clipper (limiter) circuit

    A li ti Cli (li it ) i it

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    Application: Clipper (limiter) circuit

    Application: Clampers (DC restorers) (Mch kp)

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    Application: Clampers (DC restorers) (Mch kp)

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    Application: Clampers (DC restorers) (Mch kp)

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    Application: Clampers (DC restorers) (Mch kp)

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    Application: Voltage multiplier

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    Application: Voltage multiplier

    Application: Voltage multiplier

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    Application: Voltage multiplier