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CO2005: Electronics I
Diode Circuits
張大中
中央大學 通訊工程系
[email protected]
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
1
Rectifier Circuits
 A diode rectifier forms the first stage of a dc power supply. Rectification is the process of
converting an alternating (ac) voltage into one that is limited to one polarity.
 Rectification: half-wave rectification and full-wave rectification
half-wave
rectification
中央大學通訊系 張大中
full-wave
rectification
Electronics I, Neamen 3th Ed.
2
Half-Wave Rectification
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
3
Q-point Analysis of Half-Wave Rectification
 Load line Concept for Q-point
 Battery Charger
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
4
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
5
Full-Wave Center- Tapped Transformer Rectification
 The full-wave rectifier inverts the negative portions of the sine wave so that a unipolar
output signal is generated during both halves of the input sinusoid.
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
6
Full-Wave Bridge Rectifier
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
7
Full-Wave Bridge Rectifier
 Full-wave bridge rectifier circuit to produce negative output voltages
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
8
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
9
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
10
Filter Circuit for Diode Rectifier
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
11
Analysis of Filter Circuit for Diode Rectifier
After the output has reached the peak value , vo (t )  VM e  t '/ RC
VL  VM eT '/ RC
 T 
Vr  VM  VL  VM (1  e T  / RC )  VM 

RC


 Tp 
 T 
As RC  T , T   Tp , and Vr  VM 

V


M

 RC 
 RC 
1
V
Tp 
, Vr  M
2f
2 fRC
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
12
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
13
Current in the Filter Circuit for Diode Rectifier
iD  iC  iR
dvo vo
iD  C

dt R
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
14
Detectors
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
15
Voltage Doubler Circuit
 There are also voltage tripler and voltage quadrupler circuits. These circuits provides a
means by which multiple dc voltage can be generated from a single ac source and power
transformer.
+
-
中央大學通訊系 張大中
+
Electronics I, Neamen 3th Ed.
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Zener Diode Circuits
 Zener Voltage Reference Circuit
I Z maximum : VPS maximum and I L minimum
Ri 
VPS (max)  VZ
I Z (max)  I L (min)
[VPS (min)  VZ ]  [ I Z (max)  I L (min)]
I Z minimum : VPS minimum and I L maximum
Ri 
 [VPS (max)  VZ ]  [ I Z (min)  I L (max)]
VPS (min)  VZ
I Z (min)  I L (max)
Choose I Z (min)  0.1I Z (max), we have
I Z (max) 
I L (max)[ VPS (max)  VZ ]  I L (min)[ VPS (min)  VZ ]
VPS (min)  0.9VZ  0.1VPS (max)
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
17
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
18
Zener Resistance and Percentage Regulation
 Because of the Zener resistance, the output voltage will not remain constant.
 Source regulation: a measure of the change in output voltage with a change in source
voltage.
Source regulation (%) 
vL
 100%
vPS
 Load regulation: a measure of the change in output voltage with a change in load current.
vL,no load  vL,full load
Load regulation (%) 
 100%
vL, full load
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
19
Ri  15.3
I L  0 ~ 100mA
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
20
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
21
Clipper Circuits
 Clipper circuits are used to eliminate portions of a signal that are above or/and below a
specified level.
 Transfer characteristics of a limiter circuits
 Single diode clipper
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
22
Parallel-Based Clipper
if VB  V  VI
then VO  VB  V
if VI  V  VB
then VO  V  VB
if  VB  V  VI
then VO  VB  V
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
23
Parallel-Based Clipper
if VI  V  VB1
then VO  V  VB1
and if  VB 2  V  VI
then VO  VB 2  V
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
24
Series-Based Clipper
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
25
Clampers
 Clamping shifts the entire signal voltage by a dc level. The distinguishing feature of a
clamper is that it adjusts the dc level without needing to know the exact waveform.
vo (t )  vC  vI  (VM  V )  VM sin t
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
26
Clampers
 Clamping Circuit Including an Independent Voltage Source
vo (t )  vC  vI  (VM  VB  V )  VM sin t
 VB  V  VM (sin t  1)
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
27
Analysis of Single Diode Circuits
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
28
Analysis of Two-Diode Circuit
Diode States :
(1) D1 off, D2 off
(2) D1 off, D2 on
(3) D1 on, D2 on
(4) D1 on, D2 off
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
29
Analysis of Two-Diode Circuit (1)
 D1: off, D2: on
Let V   V   V .
If D1 is off, then D2 is always on.
D2 on : V   V   V ,
iR1 
V   V  V 
R1  R2
, vo  V   iR1  R1
D1 off : v I  v  V ,
vo
v '  V   iR 2  R2 , iR 2  iD 2  iR1
V   iR1  R1
v 'V
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
vI
30
Analysis of Two-Diode Circuit (2)
 D1: on, D2: on
D1 on : vI  v 'V ,
v '  vI  V , iR 2 
vI  V  V 
R2
D2 on : V   v 'V  vI ,
V   vI
vo  vI , iR1 
R1
vo
V
v 'V
v 'V
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
V
vI
31
Analysis of Two-Diode Circuit (3)
 D1: on, D2: off
D1 on : vI  V  V  ,
v '  vI  V , iR 2 
vI  V  V 
R2
D2 off : V   v 'V  vI ,
vo  V  , iR1  0
V

vo
V
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
vI
32
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
33
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
34
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
35
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
36
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
37
Diode Logic Circuits
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
38
Photodiode Circuit
 If the photon intensity is zero, the only current through the diode is the reverse-saturation
current, which is normally very small.
 Photons striking the diode create excess electrons and holes in the depletion region. The
electric field separates these excess carriers and sweeps them out of the depletion region,
thus creating a photocurrent in the reverse-bias direction.
I ph  eA
 : quantum efficiency , e : electronic charge
 : photon flux density, A : junction area
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
39
Light-Emitting Diode (LED) Circuits
中央大學通訊系 張大中
Electronics I, Neamen 3th Ed.
40