Transcript Diode Circuits

Microelectronics
Circuit Analysis and Design
Donald A. Neamen
Chapter 2
Diode Circuits
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-1
In this chapter, we will:
 Determine the operation and characteristics of
diode rectifier circuits, which is the first stage of
the process of converting an ac signal into a dc
signal in the electronic power supply.
 Apply the characteristics of the Zener diode to a
Zener diode voltage regulator circuit.
 Apply the nonlinear characteristics of diodes to
create waveshaping circuits known as clippers
and clampers.
 Examine the techniques used to analyze circuits
that contain more than one diode.
 Understand the operation and characteristics of
specialized photodiode and light-emitting diode
circuits.
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-2
Block Diagram
for ac to dc Converter
The diode rectifier, filter, and voltage regulator are diode circuits.
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-3
Problem-Solving Technique:
Diode Circuits
1. Determine the input voltage condition such
that the diode is conducting (on).
a. Find the output signal for this condition.
2. Determine the input voltage such that the
diode is not conducting (off).
a. Find the output signal for this condition.
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-4
Half-Wave Rectifier
Voltage Transfer
Characteristics
Neamen
Microelectronics, 4e
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Chapter 2-5
Signals of Half Wave Rectifier
Input voltage
Output voltage
Diode voltage
Neamen
Microelectronics, 4e
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Chapter 2-6
Load Line Analysis
Load line when vS
is at its maximum
forward voltage.
Load line when vS
is at its most
negative value.
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-7
Load Line (con’t)
As vS varies with time, the load line also changes, which
changes the Q-point (vD and iD) of the diode.
Neamen
Microelectronics, 4e
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Chapter 2-8
Half-Wave Rectifier as
Battery Charger
Neamen
Microelectronics, 4e
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Chapter 2-9
Full-Wave Rectifier
Voltage transfer characteristics
Input and output waveforms
Neamen
Microelectronics, 4e
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Chapter 2-10
Full-Wave Bridge Rectifier
When vS is positive, D1 and D2 are turned on (a). When vS is negative, D3 and
D4 are turned on (b).
In either case, current flows through R in the same direction, resulting in an
output voltage, vO, shown in (c).
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-11
Full-Wave Bridge Rectifier
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-12
Output Voltage of Full-Wave Rectifier
with RC Filter
The ripple on the ‘dc’ output is
Neamen
VM
1
Vr 
where f 
2 fRC
2TP
Microelectronics, 4e
McGraw-Hill
Chapter 2-13
Output Voltage of Full-Wave Rectifier
with RC Filter
t 1

T 
2Vr
VM
Diode conducts current for only a small portion of the period.
Neamen
Microelectronics, 4e
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Chapter 2-14
Equivalent Circuit During
Capacitance Charging Cycle
i C  CVM t
iC , peak  CVM t
2Vr
t 
VM
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-15
PSpice Schematic of Diode
Bridge Circuit
Steady state output voltage for a
60Hz sine wave input with peak
value of 13.4V.
Neamen
Microelectronics, 4e
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Chapter 2-16
Demodulation of AmplitudeModulated Signal
Modulated input signal
Detector circuit
Demodulated output
signal
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Chapter 2-17
Voltage Doubler Circuit
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Chapter 2-18
Equivalent Circuits for
Input Cycles
Negative input cycle
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Positive input cycle
Chapter 2-19
Voltage Regulator
VZ
IL 
RL
VPS  VZ
II 
Ri
IZ  II  IL
The characteristics of the Zener diode determines VL.
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-20
Design Example 2.5
Neamen
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Chapter 2-21
Load Line Analysis
The reverse bias I-V is important for Zener diodes.
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-22
Voltage Rectifier with
nonzero Zener resistance
The Zener diode begins to conduct when VPS = VZ.
When VPS ≥ VZ:
VL = VZ
IL = VZ/RL,, but VZ ≠ constant
I1 = (VPS – VZ)/Ri
IZ = I1 - IL
Neamen
Microelectronics, 4e
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Chapter 2-23
Voltage Transfer Characteristics of
Limiter Circuit
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Chapter 2-24
Single Diode Clipper
Neamen
Microelectronics, 4e
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Chapter 2-25
Additional
Diode
Clipper
Circuits
Neamen
Microelectronics, 4e
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Chapter 2-26
Parallel-Based Diode
Clipper Circuit
Neamen
Microelectronics, 4e
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Chapter 2-27
Series-Based
Diode Clipper
Circuits
Neamen
Microelectronics, 4e
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Chapter 2-28
Parallel-Based Clipper Circuit Using
Zener Diodes
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Chapter 2-29
Diode Clamper Circuit
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Chapter 2-30
Diode Clamper Circuit with Voltage
Source
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Chapter 2-31
Diode and Resistor In Series
Voltage shift between input and output voltages in transfer
characteristics is because the diode only conducts when v1 ≥ Vg.
Neamen
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Chapter 2-32
Diode with Input Voltage Source
Output voltage is a constant when the diode is not conducting,
when v1 ≥ Vs - Vg.
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Chapter 2-33
2 Diode Circuit
Voltage transfer characteristics
Neamen
Microelectronics, 4e
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Chapter 2-34
Problem-Solving Technique:
Multiple Diode Circuits
1. Assume the state of the diode.
a. If assumed on, VD = Vg
b. If assumed off, ID = 0.
2. Analyze the ‘linear’ circuit with assumed
diode states.
3. Evaluate the resulting state of each diode.
4. If any initial assumptions are proven
incorrect, make new assumption and return
to Step 2.
Neamen
Microelectronics, 4e
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Chapter 2-35
Exercise problem
D1 is not on.
D2 is on.
This pins VO to -0.6V
Neamen
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Chapter 2-36
Diode Logic Circuits:
2-Input OR Gate
V1 (V) V 2 (V) VO (V)
0
0
0
5
0
4.3
0
5
4.3
5
5
4.3
Vg = 0.7V
Neamen
Microelectronics, 4e
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Chapter 2-37
Diode Logic Circuits:
2-Input AND Gate
V
1 V
2 V
O
( V ) ( V ) ( V )
0
0
0
5
0
0
0
5
0
5
5
4.3
Vg = 0.7V
Neamen
Microelectronics, 4e
McGraw-Hill
Chapter 2-38
Photodiode Circuit
Neamen
Microelectronics, 4e
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Chapter 2-39
Optoisolator
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Chapter 2-40
Design DC Power Supply Circuit
Neamen
Microelectronics, 4e
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Chapter 2-41