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Chapter 10
Diodes
Basic Diode Concepts Load-Line Analysis of Diode Circuits Zener-Diode Voltage-Regulator Circuits Ideal-Diode Model Piecewise-Linear Diode Models Rectifier Circuits Wave-Shaping Circuits Linear Small-Signal Equivalent Circuits
Chapter 10
Diodes
1. Understand diode operation and select diodes for various applications. 2. Analyze nonlinear circuits using the graphical load-line technique.
3. Analyze and design simple voltage- regulator circuits.
4. Solve circuits using the ideal-diode model and piecewise-linear models.
5. Understand various rectifier and wave- shaping circuits.
6. Understand small-signal equivalent circuits.
Shockley Equation
= exp 1 T
D D s nV
v i I q
kT VT =
k = 1_._ 38 × 10 –23^ J/K is Boltzmann’s constant and q = 1_._ 60 × 10 –19^ C is the magnitude of the electrical charge of an electron. At a temperature of 300 K, we have VT ≅ 26 mV
Zener Diodes
Diodes that are intended to operate in the breakdown region are called Zener diodes.
ZENER-DIODE VOLTAGE-
REGULATOR CIRCUITS
A voltage regulator circuit provides a nearly constant voltage to a load from a variable source.
VSS + RiD + vD = 0
Load-Line Analysis of
Complex Circuits
PIECEWISE-LINEAR DIODE
MODELS
v = Ra i + V a
r
L
V
I T
C =
r L m
V
V ≅ V −
Peak Inverse Voltage
An important aspect of rectifier circuits is the peak inverse voltage (PIV) across the diodes.
r
L
V
I T
C
The capacitance required for a full-wave rectifier is given by:
LINEAR SMALL-SIGNAL
EQUIVALENT CIRCUITS
The small-signal equivalent circuit for a diode is a resistance.
D D Q D D v dv i di ∆ ⎟⎟⎠
⎞ ⎜⎜⎝
⎛ ∆ ≅
− 1
⎥
⎥ ⎦
⎤ ⎢
⎢ ⎣
⎡ ⎟⎟⎠
⎞ ⎜⎜⎝ ≅⎛ D Q
d D dv
r di
d
d d (^) r i = v
Notation for Currents and
Voltages in Electronic
Circuits
v (^) D and iD represent the total instantaneous diode voltage and current. At times, we may wish to emphasize the time-varying nature of these quantities, and then we use vD ( t ) and iD ( t )
V (^) DQ and I (^) DQ represent the dc diode current and voltage at the quiescent point.
v (^) d and id represent the (small) ac signals. If we wish to emphasize their time varying nature, we use vd ( t ) and id ( t ).
