Download presentation
Presentation is loading. Please wait.
1
C H A P T E R 4 Diodes (non-linear devices)
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
2
Ideal Diode Microelectronic Circuits, Sixth Edition
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
3
Figure 4.2 The two modes of operation of ideal diodes and the use of an external circuit to limit (a) the forward current and (b) the reverse voltage. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
4
Simple diode application: rectifier
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
5
Figure 4.4 Circuit and waveforms for Example 4.1.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
6
Diode logic gates Figure 4.5 Diode logic gates: (a) OR gate; (b) AND gate (in a positive-logic system). Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
7
Example 4.2. Microelectronic Circuits, Sixth Edition
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
8
Examples Figure E4.4 Microelectronic Circuits, Sixth Edition
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
9
Thermal voltage Terminal Characteristics of Junction Diodes
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
10
i=-IS Forward bias region: v>0 Reverse bias region: v<0
Terminal Characteristics of Junction Diodes Forward bias region: v>0 Reverse bias region: v<0 Break down region: v<-Vzk i=-IS Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
11
Effect of Temperature Figure 4.9 Temperature dependence of the diode forward characteristic. At a constant current, the voltage drop decreases by approximately 2 mV for every 1°C increase in temperature. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
12
Diode Exponential Model
Figure 4.11 Graphical analysis of the circuit in Fig using the exponential diode model. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
13
Diode Constant-Voltage-Drop Model
Figure 4.12 Development of the diode constant-voltage-drop model: (a) the exponential characteristic; (b) approximating the exponential characteristic by a constant voltage, usually about 0.7 Vi; (c) the resulting model of the forward–conducting diodes. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
14
Diode Ideal Model Microelectronic Circuits, Sixth Edition
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
15
Figure 4.13 Development of the diode small-signal model.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
16
Example Microelectronic Circuits, Sixth Edition
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
17
Use Diode Forward Drop in Voltage Regulation.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
18
Operation in the Reverse Breakdown Region
– Zener Diodes – Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
19
Zener Diode Model Microelectronic Circuits, Sixth Edition
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
20
Example Microelectronic Circuits, Sixth Edition
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
21
The diode is in parallel with the load
Use of Zener Diode Shunt Regulator The diode is in parallel with the load Temperature Sensing - Using temperature coefficient (temco) -2mV/0C Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
22
Rectifier Circuits Figure 4.20 Block diagram of a dc power supply.
ripple Figure 4.20 Block diagram of a dc power supply. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
23
The half-wave rectifier
PIV = vS Figure 4.21 (a) Half-wave rectifier. (b) Transfer characteristic of the rectifier circuit. (c) Input and output waveforms. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
24
The full-wave rectifier
PIV = 2vS - VD Figure 4.22 Full-wave rectifier utilizing a transformer with a center-tapped secondary winding: (a) circuit; (b) transfer characteristic assuming a constant-voltage-drop model for the diodes; (c) input and output waveforms. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
25
The bridge rectifier PIV = vS - VD
Figure 4.23 The bridge rectifier: (a) circuit; (b) input and output waveforms. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
26
The peak rectifier – filtering with capacitor
Figure 4.24 (a) A simple circuit used to illustrate the effect of a filter capacitor. (b) Input and output waveforms assuming an ideal diode. Note that the circuit provides a dc voltage equal to the peak of the input sine wave. The circuit is therefore known as a peak rectifier or a peak detector. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
27
Microelectronic Circuits, Sixth Edition
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
28
Figure 4.26 Waveforms in the full-wave peak rectifier.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
29
Precision half-wave rectifier
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
30
Figure 4.28 General transfer characteristic for a limiter circuit.
Figure 4.30 Soft limiting. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
31
Figure 4.31 A variety of basic limiting circuits.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
32
Figure 4.31 A variety of basic limiting circuits.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
33
Example Microelectronic Circuits, Sixth Edition
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
34
The clamped capacitor or dc restorer with a square-wave input and no load.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
35
The clamped capacitor with a load resistance R.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
36
Voltage doubler: (a) circuit; (b) waveform of the voltage across D1.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
37
Schottky-Barrier diode (SBD): Metal anode, semiconductor cothode
Other Diode devices: Schottky-Barrier diode (SBD): Metal anode, semiconductor cothode Fast switching ON/OFF. Low forward voltage drop (0.3 – 0.5 V) Varactors: Capacitance between PN junction Changing reverse voltage, change capacitance Photodiodes: Reverse-biased PN junction illuminates Converting light signal to electrical signal LEDs: - Inverse function of photodiodes (electrical to light) Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Similar presentations
