neamen microelectronics, 4echapter 2-1 mcgraw-hill microelectronics circuit analysis and design...
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Neamen Microelectronics, 4e Chapter 2-1 McGraw-Hill
Microelectronics Circuit Analysis and Design
Donald A. Neamen
Chapter 2
Diode Circuits
Neamen Microelectronics, 4e Chapter 2-2 McGraw-Hill
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 Chapter 2-3 McGraw-Hill
Block Diagram for ac to dc Converter
The diode rectifier, filter, and voltage regulator are diode circuits.
Neamen Microelectronics, 4e Chapter 2-4 McGraw-Hill
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 Chapter 2-5 McGraw-Hill
Half-Wave Rectifier
Voltage Transfer Characteristics
Neamen Microelectronics, 4e Chapter 2-6 McGraw-Hill
Signals of Half Wave Rectifier
Input voltage Output voltage
Diode voltage
Neamen Microelectronics, 4e Chapter 2-7 McGraw-Hill
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 Chapter 2-8 McGraw-Hill
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 Chapter 2-9 McGraw-Hill
Half-Wave Rectifier as Battery Charger
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Full-Wave Rectifier
Voltage transfer characteristics
Input and output waveforms
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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).
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Full-Wave Bridge Rectifier
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Output Voltage of Full-Wave Rectifier with RC Filter
The ripple on the ‘dc’ output isP
Mr T
ffRC
VV
2
1 where
2
Neamen Microelectronics, 4e Chapter 2-14
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Output Voltage of Full-Wave Rectifier with RC Filter
Diode conducts current for only a small portion of the period.
M
r
V
V
T
t 21
Neamen Microelectronics, 4e Chapter 2-15
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Equivalent Circuit During Capacitance Charging Cycle
M
r
MpeakC
MC
V
Vt
tCVi
tCVi
2
,
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PSpice Schematic of Diode Bridge Circuit
Steady state output voltage for a 60Hz sine wave input with peak value of 13.4V.
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Demodulation of Amplitude-Modulated Signal
Modulated input signal
Detector circuit
Demodulated output signal
Neamen Microelectronics, 4e Chapter 2-18
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Voltage Doubler Circuit
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Equivalent Circuits for Input Cycles
Negative input cycle Positive input cycle
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Voltage Regulator
The characteristics of the Zener diode determines VL.
LIZ
i
ZPSI
L
ZL
III
R
VVI
R
VI
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Design Example 2.5
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Load Line Analysis
The reverse bias I-V is important for Zener diodes.
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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
Voltage Rectifier with nonzero Zener resistance
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Voltage Transfer Characteristics of Limiter Circuit
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Single Diode Clipper
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Additional Diode
Clipper Circuits
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Parallel-Based Diode Clipper Circuit
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Series-Based Diode Clipper
Circuits
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Parallel-Based Clipper Circuit Using Zener Diodes
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Diode Clamper Circuit
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Diode Clamper Circuit with Voltage Source
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Diode and Resistor In Series
Voltage shift between input and output voltages in transfer characteristics is because the diode only conducts when v1 ≥ V.
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Diode with Input Voltage Source
Output voltage is a constant when the diode is not conducting, when v1 ≥ Vs - V.
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2 Diode Circuit
Voltage transfer characteristics
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Problem-Solving Technique: Multiple Diode Circuits
1. Assume the state of the diode. a. If assumed on, VD = V
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.
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Exercise problem
D1 is not on.
D2 is on. This pins VO to -0.6V
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Diode Logic Circuits:2-Input OR Gate
V1 (V) V2 (V) VO (V)
0 0 0
5 0 4.3
0 5 4.3
5 5 4.3
V = 0.7V
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Diode Logic Circuits:2-Input AND Gate
V1 (V)
V2
(V)VO
(V)
0 0 0
5 0 0
0 5 0
5 5 4.3
V = 0.7V
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Photodiode Circuit
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Optoisolator
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Design DC Power Supply Circuit