This document discusses diodes and their applications in electronic circuits. It covers ideal and junction diodes, modeling diodes using exponential, piecewise linear, constant voltage and small signal models. It also discusses zener diodes, rectifiers, peak detectors and their usage in limiting and clamping circuits. Various diode circuits including half-wave, full-wave and bridge rectifiers as well as voltage doublers are described.

1. Diode
Electronic Circuits
CHO, Yong Heui

2. Electronic Circuits
1. Ideal diode
Nonlinear device
No voltage drop External circuits
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3. Electronic Circuits
1. Ideal diode
Rectifier: ideal diode
Output Waveform
Equivalent Circuits
Waveform of V D
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4. Electronic Circuits
1. Ideal diode
Logic circuits
Logic definition: 0 V  [0], 5 V  [1]
Y = A + B + Y = A · B · C
C
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5. Electronic Circuits
2. Junction diode
Forward bias
i = I s (e v/nVT – 1)
I S ( T ) : reverse-biased saturation current
depends on Temp. and junction area
≈ 10 -15 (doubles at every 5 ºC)
V T = kT/q
V 2 – V 1 = 2.3nV T ·log(I 2 /I 1 )
2.3 V T is theoretical threshold swing : 60 mV
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6. Electronic Circuits
2. Junction diode
Temperature dependence
Reverse-bias / Breakdown regions
i = I s (e v/nVT – 1) i ≈ I s when v is negative and more than a few V T
Reverse current : doubles for every 10
ºC
Zener breakdown and avalanche breakdown
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7. Electronic Circuits
3. Modeling
Exponential model
I D = (V DD – V D ) / R
I D = I s e v/nVT
The exponential model:
I D = I s e v/nVT
Graphical
Analysis
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8. Electronic Circuits
3. Modeling
Piecewise linear model
i D = 0, v D ≤ V D0
i D = (v D - V D0 ) / r D , v D ≥ V D0
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9. Electronic Circuits
3. Modeling
Constant voltage model
i D = 0, v D ≤ V D
i D = undefined , v D ≥ V D
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10. Electronic Circuits
3. Modeling
Small signal model
I D = I s e v/nVT
v D (t) = V D + v d (t)
i D (t) ≈ I D (1 + v d /nV T ) , v d /nV T ≪ 1
i D (t) = I D + I D v d /nV T = I D + i d
i d = I D v d /nV T = v d / r D
r D = nV T / I D : small-signal resistance
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11. Electronic Circuits
4. Zener diode
Breakdown region
At Bias point, ΔV = ΔI ·r Z
r Z : dynamic resistance
V Z = V Z0 + r Z ·I Z
Almost linear i-v characteristics
I ZK : minimum current for the operation of Zener diode
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12. Electronic Circuits
4. Zener diode
Shunt regulator
Shunt Regulator: V Z = 6.8V, I Z = 5 mA, r Z = 20Ω, and I ZK = 0.2 mA
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13. Electronic Circuits
4. Zener diode
Shunt regulator
Shunt Regulator: V Z = 6.8V, I Z = 5 mA, r Z = 20Ω, and I Z K = 0.2 mA
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14. Electronic Circuits
4. Zener diode
Shunt regulator
Shunt Regulator: V Z = 6.8V, I Z = 5 mA, r Z = 20Ω, and I Z K = 0.2 mA
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15. Electronic Circuits
5. Rectifier
DC power supply
V1 / V2 = N1 / N2
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16. Electronic Circuits
5. Rectifier
Half-wave rectifier
v O = 0, v S < V D0
R R
vO = vS - V D0
R + rD R + rD v S ≥ V D0
≈ v S – V D0 , for r D ≪ R
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17. Electronic Circuits
5. Rectifier
Full-wave rectifier
PIV = 2V S – V D0
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18. Electronic Circuits
5. Rectifier
Bridge rectifier
v D 3 (reverse) = v O + v D2 (forward)
PIV = V s -2V D + V D = V s - V D
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19. Electronic Circuits
5. Rectifier
Peak detector
Ideal case
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20. Electronic Circuits
5. Rectifier
Peak rectifier
t1 < t < t2
V r = V P – v O (T-ΔT) =
i Dav = I L (1 + π√2V p /V r ) i Dmax = I L (1 + 2π√2V p /V r )
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21. Electronic Circuits
5. Rectifier
Rectifier with RC load
Precision half-wave rectifier
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22. Electronic Circuits
6. Limiter
Limiting circuits
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23. Electronic Circuits
6. Limiter
Clamping circuits
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24. Electronic Circuits
6. Limiter
Voltage doubler
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