Slide điện tử tương tự chapter 1 diodes and applications

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Electronics Circuits I

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Chapter 1: Diodes and applications
Dr. Pham Nguyen Thanh Loan

Ha Noi, 21/8/2013
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Chapter 1: Diode & applications

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Contents
 Diode – Structure, operation and equivalent circuit
 Rectifiers circuits
 Limiters circuits
 Double voltage and so on
 Zener diode and its applications

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Depletion region: no carriers
Ion located at the interfaces with P/N  barrier voltage VD  drift
current IS (idrift)
Diffusion phenomenon: flow of charges from high concentration
region to lower concentration region  ID (idiff)
Equilibrium of PN junction: Is + ID = 0

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PN Junction

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Diode structure

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PN junction and its symbol: Diode

Kathode (K)

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Anode (A)

Kathode (K)

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Anode (A)

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FORWARD BIAS
ID ↑ very fast

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Two terminals
Current ON in one direction
VD = 0V

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Model of ideal diode

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REVERSE BIAS
ID ≈ 0
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Model of practical diode (VD ≠ 0)
FORWARD BIAS: applied

voltage > VD
VD ≈ 0.7V (Si)
VD ≈ 0.3V (Ge)
 Voltage drop on diode = VD
 REVERSE BIAS:

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

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Leakage current IS ≈ 0

 Open circuit

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PRACTICAL Diode

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PRACTICAL Diode

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PRACTICAL Diode (VD ≠ 0)

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ID(mA)

0.3(Ge)

0.7(Si)

VD(V)

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Is(Si)=10nA

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Is(Ge)

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(Ge)

Is=reverse saturation current

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PRACTICAL Diode

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PRACTICAL Diode - multimeter

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PRACTICAL Diode - multimeter

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Large signal model

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Small signal model

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Limiters
Double voltage

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Half wave
Full wave
Wien bridge
Using capacitor (filters)

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Rectifiers

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Applications

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Rectifiers

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Half wave

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Half wave:
Diode: ON
Vout = Vin - VD

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Diode: OFF, ID=0
Vout = 0

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half positive periode
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1

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Half wave with transformer

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 Example: Analyze the following circuit

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Fullwave rectifier

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Waveform of input and output signal

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Fullwave rectifier: schematic

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Fullwave rectifier: operation

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Fullwave rectifier: operation

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NOTES: CURRENT
flows through load
resistor following a
unique direction and

can’t be reversed

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Determine PIV

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 PIV = VP(sec) + 0.7V

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Ex: Determine PIV

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