Sedra/Smith Microelectronic Circuits 6/E Chapter 3: Diodes

Transcription

Sedra/Smith Microelectronic Circuits 6/E Chapter 3: Diodes
Sedra/Smith
Microelectronic Circuits 6/E
Chapter 3: Diodes
S. C. Lin, EE National Chin-Yi University of Technology
1
【Outline】
3.1 The Ideal Diode
3.2 Terminal Characteristics of Junction Diodes
3.3 Modeling the Diode Forward Characteristic
3.4 Operation in the Reverse Breakdown Region — Zener
Diodes
3.5 Rectifier Circuits
3.6 Limiting and Clamping Circuits
3.7 Special Diode Types
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3.1 The Ideal Diode
i
+ v −
(a) diode circuit symbol
(b) i–v characteristic
i
i
+ v −
v<0⇒i =0
(c) equivalent circuit in the
reverse direction
+ v −
i >0⇒v=0
(d) equivalent circuit in
the forward direction.
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The two modes of operation of ideal diodes and the use of an
external circuit.
+10V
10mA
1kΩ
+10V
0mA
1kΩ
+
+
0V
−
10V
−
(a) the forward current
(b) the reverse voltage
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Vp
vi
+ vD −
t
0
iD
vi
(a) Input waveform.
iD
+ vD = vi −
R
+
vo = vi
−
(c) Equivalent circuit when vi ≥ 0.
0
vi
iD = 0
R
+
vo = 0
−
vi ≤ 0
vi ≥ 0
Vp
R
(b) Rectifier circuit.
+ vD = 0 −
vi
+
vo
−
(d) Equivalent circuit when
vi ≤ 0
.
vo
t
(e) Output waveform.
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Example 3.1 Fig.3.4(a), shows a circuit for charging a 12-V battery.
If vs is sinusoid with 24-V peak amplitude, (a) Find the fraction of
each cycle during which the diode conducts. (b) Also find the peak
value of the diode current and (c) the maximum reverse-bias voltage
that appears across the diode.
iD
100Ω
vs
Method 1:
12V
24V
VD
12V
αθ
(a ) 24sin α = 12 ⇒ α = 30o
2θ = 180o − 2α = 120o
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Method 2:
24V
VD
12V
θ
θ
(a)24 cos θ = 12 ⇒ θ = 60o
Conduction angle = 2θ = 120o ▲
(b)I D (max) =
24 − 12
= 0.12A ▲
100
(c)The maximum reverse voltage across the diode:
VD (max) = 24 + 12 = 36V ▲
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3.1.3 Another Application: Diode Logic Gates
+5V
vA
R
vB
vC
vY
(a) OR gate
vA
(b) AND gate
vB
R
vY
vC
vA
vB
vC
vY
vA
vB
vC
vY
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Example 3.2 Assuming the diode to be ideal, Find the values of I and
V in the circuit of Fig. (a) and (b)
+10V
Sol:
Asssume that both diodes are conducting
10kΩ
I D2
I
D1
5kΩ
−10V
D2
VB = 0 and V = 0
+
V
−
ID =
2
(10 − 0)V
= 1mA
10kΩ
Writting a node equation at B (K.C.L)
0 − (−10)
I +1 =
⇒ I = 1mA
5
Results in I = 1mA,
Thus D1 is conducting as originally assumed
and the find resuit is I = 1mA and V = 0V ▲
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Sol:
+10V
.
We asssume that both diodes are conducting
5kΩ
I D2
D1
I
D2
then VB = 0 and V = 0
ID =
+
V
−
2
(10 − 0)V
= 2mA
5kΩ
The node equation at B is
0 − (−10)
⇒ I = −1mA
10
(This is not possible)
I +2=
10kΩ
−10V
Our assumption is not correct, we start again assuming that D1 is OFF and D2 is ON.
The current I D is given by
2
10 − (−10)
= 1.33mA
15
VB = −10 + 10 ⋅ 1.33 = 3.3V
ID =
2
Thus D1 is reverse biased as assumed ∴ I = 0A and V = 3.3V ▲
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3.2 Terminal Characteristics junction diode
i
(1) The forward-bias region
determined by v > 0
1
(2) The reverse-bias region
determined by − VZK < v < 0
−VZK
3
2
Expanded scale
0
0.5V
0.7V
v
(3) The breakdown-bias region
determined by v < −VZK
i
+ v −
Figure 3.8 The diode i–v relationship with some scales expanded
and others compressed in order to reveal details.
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3.2.1 The Forward-bias region
(
)
i = I s ev / nV − 1
T
(3.1)
(a ) I s is saturation current , another name for I s is the scale current.
(b) I s is a constant for a given diode at a given temperature.
(c) I s is directly propotional to the across-sectional area of the diode.
(d) I s For "small-signal" diode intened for low-power application,
I s is on the order of 10-15A
(e) I s a very strong function of temperature. As a rule of thumb,
I s doubles in value for every 5oC rise in temperature.
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VT : Thermal voltage
K ⋅T
VT =
q
(3.2)
where K = Boltzmann's constant = 1.38 × 10-23 Joules/Kelvin
T = The absolute temperature in Kelvin = 273+temperature oC
q = The magnitude of electronic charge = 1.60 × 10−19 Coulomb
At room temperature(20o C), VT ≅ 25.2mV.
At room temperature(27o C), VT ≅ 26mV.
n
n :1 ↔ 2, Depending on the material and
the physical structure of the diode.
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the forward direction i >> I s
i
i ≅ Ise
⇒ v = nVT ln
Is
If the voltage is v1 (v2 ), the diode current I1 ( I 2 )
v / nVT
thus
i1 ≅ I s ev1 / nVT
and i2 ≅ I s ev2 / nVT
i2
= e( v −v ) / nV
i1
2
1
T
i2
i2
v2 − v1 = nVT ln = 2.3nVT log
i1
i1
(3.5)
This equation simply states that for a decade changes in current,
the diode voltage drop changes by 2.3nVT ≈ 60mV,for n = 1
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Example: Design the circuit in below Figure to provide an output
voltage of 2.4V. Assume that diode available have 0.7V drop
at 1mA and that ΔV= 0.1V/decade changes in current.
Sol:
Refer Fig.a to obtain vo = 2.4V
+10V
each diode must have a voltage drop of 0.8V
thus
i2
v2 − v1 = 2.3nVT log
i1
R
vo
i2
i2
0.1 = 2.3 ⋅ 2 ⋅ 25 ⋅10 ⋅ log = 0.1log
i1
i1
−3
i2 = 10i1 = 10mA
The value of R is determined from
(10 − 2.4)V
R=
= 760Ω ▲
10mA
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T2
i
>
T1
−2mV/ o C
I
v
Figure 3.9 Illustrating the 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.
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Example 3.3 : A silicon diode said to be a 1-mA device displays a
forward voltage of 0.7V at a current of 1mA. Evaluate the
junction scaling constant Is in the event that n is either 1or 2,
what scaling constants would apply for a 1-A diode of the
same manufacture that conducts 1A at 0.7V
Since i ≅ I s ev / nVT ⇒ I s = i ⋅ e − ( v / nVT )
for the 1 − mA diode.
If n = 1
If n = 2
I s = 1×10−3 × e −700 / 25 = 6.9 × 10−16 A ▲
I s = 1× 10−3 × e −700 / 50 = 8.3 × 10−10 A ▲
The diode conducting 1A at o.7V corresponds to 1000 1mA in parallel
with a total junction area 1000 times greater. Thus it is also 1000 times
greater being 1pA and 1µA , respectively for n = 1 and n = 2 .
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3.2.2 The Reverse-Bias Region
If v is negative and a few times large then VT (25mV)
in magnitude the diode current becomes
i ≅ − I s (Saturation current)
I s : It doubles for every 10o C rise in temperature
I s2 = I s1 ⋅ 2(T2 −T1 /10)
3.2.3 The Breakdown Region
⎧ Z: Zener
v < −VZK ⎨
⎩ K: Knee
In the breakdown region the reverse current increase rapidly
with the associated increase in voltage drop very small
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3.3 Modeling the diode forward characteristic
3.3.1 The Exponential Model.
ID
R
+
VDD
VD
−
⎧VDD > 0.5V
Assuming that ⎨
(3.6)
⇒ I D = I s eVD / nVT
⎩ ID > Is
The other equation that governs circuit operation is obtained by writing a
loop equation by KVL, resulting in I D =
VDD − VD
R
(3.7)
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3.3.2 Graphical Analysis Using the Exponential Model.
i
VDD
R
Q (Operating point)
ID
0
−1
Slop =
R
VD
VDD
v
Figure 3.11 Graphical analysis of the circuit in
Fig. 3.10 using the exponential diode model.
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3.3.3 Iterative analysis using the exponential model
Example3.4 determine the current I D and the diode voltage VD for the circuit
in Fig.3.10 with VDD = 5V and R = 1kΩ, assume that the diode has a current
of 1mA at voltage of 0.7V and that its voltage drop changes by 0.1V for every
decade change in current.
Sol : We assume that VD = 0.7V, I D = 1mA
VDD − VD (5 − 0.7)V
=
= 4.3mA
ID =
R
1kΩ
I
V2 − V1 = 2.3 ⋅ n ⋅ VT ⋅ log 2
I1
V2 = V1 + 0.1 ⋅ log
I2
( n = 2, 2.3 ⋅ n ⋅VT ≅ 0.1V )
I1
4.3mA
= 0.763V
V2 = 0.7 + 0.1 ⋅ log
1mA
The first iteration are I D = 4.3mA, VD = 0.763V
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We assume that VD = 0.763V, I D = 4.3mA
VDD − VD (5 − 0.763)V
=
= 4.237mA
1kΩ
R
4.237mA
V2 = 0.763 + 0.1 ⋅ log
= 0.762V
4.3mA
ID =
The second iteration are I D = 4.237mA, VD = 0.762V
We assume that VD = 0.762V, I D = 4.237mA
VDD − VD (5 − 0.762)V
ID =
=
= 4.238mA
R
1K Ω
4.238mA
V2 = 0.762 + 0.1⋅ log
= 0.762V
4.237mA
Because I D did not change by much stop here and the solution is
I D = 4.237mA and VD = 0.762V
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3.3.5 The Constant-Voltage-Drop Model. (Rapid analysis)
iD (mA)
VD = 0.7V
⎧ iD = 0,
⎨
⎩iD = (vD − 0.7V) / R
VD
vD ≤ 0.7V
vD ≥ 0.7V
vD (V)
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The constant-voltage-drop model of the diode forward characteristics
and its equivalent-circuit representation.
iD (mA)
12
ID
10
+
8
vD
6
−
VD = 0.7V
VD = 0.7V
4
2
0
0.2
0.4
0.6
0.8
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1.0 v (V)
D
24
Example: Repeat the problem in example 3.4, utilizing the
constant-voltage-drop model whose parameters are given
in Fig 3.12 . Find I D and VD .
ID
ID
R
+
VDD
VD
−
+
vD
−
VD = 0.7V
Sol:
VDD − VD (5 − 0.7)V
ID =
=
= 4.3mA
R
1kΩ
VD = VD = 0.7V
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3.3.7 The Diode Small-Signal Model.
iD = I S evD / nVT
(3.8)
vD (t ) = VD + vd (t )
(3.9)
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iD (t ) = I S evD (t ) / nVT = I S e[VD + vd (t )] / nVT
= I S eVD / nVT ⋅ evd (t ) / nVT
ID
= I D ⋅ evd (t ) / nVT
(3.12)
If the signal vd (t ) is kept sufficiently small
vd (t )
such that
<< 1
nVT
Thus, the approximate expression
⎛
vd ⎞
iD (t ) = I D ⋅ ⎜1 +
⎟
⎝ nVT ⎠
(3.14)
Small-signal approximation
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We have
iD (t ) = I D +
ID
vd
nVT
(3.15)
id
ID
vd
nVT
vd nVT
rd ≡
=
id
ID
where id =
(3.17)
(3.18)
The rd is diode smal-signal
resistance,
and called incremental resistance)
In Fig.3-13(b), which is equal to the slope of the tangent to the
i - v curve at the operating point Q is equal to the small-signal
conductance.
that is, rd =
1
⎡ ∂id ⎤
⎢ ∂v ⎥
⎣ d ⎦i
d
(3.19)
=ID
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Example 3.6: Consider the circuit shown in Fig 3.15 a string of three
diode is used to provide a constant voltage of about 2.1V, we want to
calculate the percentage change in this regulated voltage cause by :
(a) ±10% change in the power-supply voltage
(b) Connection of a 1kΩ load resistance. Assume n=1
Sol:
with no load
(10 − 2.1)V
= 7.9mA
I=
1kΩ
nVT 25mV
=
= 3.2Ω
rd =
I
7.9mA
The total incremental resistance
r = 3rd = 9.6Ω
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r
0.0096
= ±1
= ±9.5mV ▲
(a) ∆vo = ±1
r+R
0.0096 + 1
This implies a change of about ± 3.2mV per diode.
(b)When a load resistance of 1kΩ is connected across
the diode string. it draws a current of 2.1mA
∴∆vo = −2.1× r = −2.1× 9.6 = −20mV. ▲
this implies that the voltage across
each diode decreses by about 6.7mV.
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3.4 Operation in the reverse breakdown region
-Zener diode
(1) rZ is the inverse of the slop of the
almost-linear i - v curve at point Q
(2) rZ : increase resistance
(3) Typically, rZ i s in the range
of a few ohms to a few ten ohms
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Vz = Vzo + I z rz
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(3.20)
32
3.4.2 Use of the Zener as a Shunt Regulator
Example 3.7: The 6.8V Zener diode in the circuit of Fig.3.19(a)
is specified to have VZ = 6.8V at I Z = 5mA, rz = 20Ω and
I ZK = 0.2mA, the V + is 10V ± 1V.
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(a) Find Vo with no load and with V + at its nominal value.
Sol: first we must determine the value of V
zo
Vzo = Vz − I z rz = 6.8 − 5 ⋅10−3 × 20 = 6.7 V
10 − 6.7
Iz = I =
= 6.35mA
0.5 + 0.02
Thus Vo =Vz = Vzo + Iz rz = 6.83V ▲
(b) Find change in Vo resulting from the ± 1V change in V+ .
Sol: ∆ Vo = ∆V +
rz
20
= ±1 ×
= ±38.5mV
R + rz
500 + 20
line regulation ≡ ∆Vo / ∆Vi = ±38.5mV/1V = ±38.5mV/V ▲
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(c) Find change in Vo resulting from connecting a load resistance RL .
that draws a current I L = 1mA, and hence find the load regulation
(∆Vo / ∆I L ) in mV/mA.
Sol:
∆ Vo = ∆I z ⋅ rz = 20Ω × −1mA = −20mV
load regulation ≡ ∆Vo / ∆I L = −20mV/mA ▲
(d)Find change in Vo when RL = 2kΩ.
Sol: RL = 2kΩ, I RL ≈ ∆I z
≈ −6.8V / 2kΩ = −3.4mA
∆ Vo = ∆I z ⋅ rz = −20 × 3.4 = −68mV ▲
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(e)Find the value of Vo when RL = 0.5kΩ.
Sol:
RL = 0.5kΩ, would draw a I L = 6.8 / 0.5 = 13.6mA.This is impassible.
because I supplied through R is only 6.4mA, therefore,
RL
the zener must be cut-off. Hence Vo = V
= 5V ▲
R + RL
+
(f) What is the minmum value of RL for which the diode
still operates region in the breakdown .
Sol:
I z = I zK = 0.2mA ⇒ Vz = VzK ≈ Vzo = 6.7V
9 − 6.7
I (min) =
= 4.6mA
0.5
I (max) = (4.6 − 0.2)mA = 4.4mA, ∴ RL =
6.7
= 1.5kΩ ▲
4.4
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3.4.3 Temperature effects, T.C or Temco
(1) VZ < 5V, dVz / dT < 0. Negative T.C
(2) VZ > 5V, dVz / dT > 0. Positive T.C
(3) VZ = 5V, dVz / dT = 0. Zero T.C
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3.5 Rectifier Circuits
Figure 3.20 Block diagram of a dc power supply.
(1) The Half-wave rectifier.
(2) The full-wave rectifier
(a) The center tap rectifier
(b) The bridge rectifier
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3.5.1 Half-Wave Rectifier.
(a) Half-wave rectifier.
(b) Equivalent circuit of the half-wave
rectifier with the diode replaced with
its battery-plus-resistance model.
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vS < VDO
⎧vO = 0,
⎪
R
⎨
v
=
⎪ O R + r (vS − VDO ), vS ≥ VDO
D
⎩
(c) Transfer characteristic of the rectifier circuit.
VD
φi = sin
Vm
−1
φi
(d) Input and output waveforms, assuming that rD << R.
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We assume vS = Vm sin α thus
1 π
VDC =
vS dα
∫
0
2π
1 π
Vm sin αdα
=
∫
0
2π
Vm
π
= (− cos α 0 )
2π
Vm
= 0.318Vm
=
π
1/ 2
⎡1
⎤
Vrms = ⎢ ∫ vS 2 dα ⎥
⎣ 2π 0
⎦
1 π 2 2
2
Vrms =
Vm sin αdα
∫
0
2π
Vm 2 π 1 1
=
( − cos 2α )dα
∫
2π 0 2 2
π
π
Vm 2 1
1
=
( α − sin 2α )
2π 2
4
0
Vm 2
=
⇒ Vrms = 0.5Vm
4
PIV = Vm (PIV : Peak inverse voltage)
VDO
φi = sin
Vm
−1
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3.5.2 The full-wave rectifier
(a) circuit
(b) transfer characteristic assuming a constant-voltage-drop
model for the diodes
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42
(c) input and output waveforms.
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We assume vS = Vm sin α thus
VDC
⎧1 π
⎫
= 2 × ⎨ ∫ vS dα ⎬
⎭
⎩ 2π 0
2 ×1 π
=
Vm sin αdα
∫
0
2π
Vm
π
= (− cos α 0 )
π
2 × Vm
= 0.636Vm
=
π
1/ 2
⎡ 2 ×1 π 2 ⎤
Vrms = ⎢
vS dα ⎥
∫
0
⎣ 2π
⎦
2 ×1 π 2 2
2
Vrms =
Vm sin αdα
∫
0
2π
2 × Vm 2 π 1 1
=
( − cos 2α )dα
∫
2π 0 2 2
π
Vm 2 1
1
=
( α − sin 2α )
4
π 2
0
Vm 2
=
⇒ Vrms = 0.707Vm
2
PIV = 2Vm (PIV : Peak inverse voltage)
VD
φi = sin
Vm
−1
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3.5.3 The Bridge Rectifier
Figure 3.27 The bridge rectifier: (a) circuit; (b) input and output waveforms.
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3.5.4 The Rectifier with a Filter Capacitor-The Peak Detector
A simple circuit used to illustrate the effect of a filter capacitor
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We assumption that RC >> T in Fig3.29(b)
The load current iL = vO / R
dv
The diode current iD = iC + iL = C I + iL
dt
(1) Derivative the Vr ( rms )
During the diode cutoff interval vo = VP − Vr
VP − Vr = VP e −T / RC
Vr = VP
V
VP
T
= P ⇒ Vr ( rms ) =
RC fRC
2 3 fRC
(2) Derivative the conduction interval ∆t
VP cos(ω∆t ) = VP − Vr
1
The angle ω∆t is very small , ∴ cos(ω∆t ) ≈ 1 − (ω∆t ) 2
2
⎡ 1
⎤
VP ⎢1 − (ω∆t ) 2 ⎥ = VP − Vr ⇒ ω∆t = 2Vr / VP
(3.30)
⎣ 2
⎦
We note that when Vr << VP the conduction angle ω∆t will be small
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49
(3) Dertermine the average diode current during conduction, iDav
the charge that the diode supplies to the capacitor
QSupplied = iC ( av ) ⋅ ∆t
(a)
the charge that the capacitor loses
Qlost = C ⋅Vr
(b)
C ⋅ Vr
The(a) equal to (b) ⇒ iC ( av ) =
∆t
VP
VP
Using(3.29a ) Vr =
,
⇒C =
fRC
Vr fR
2Vr
and(3.30) ω∆t = 2Vr / VP ⇒ ∆t =
ω VP
VP
⋅V r
f V rR
2π VP VP
C ⋅Vr
we obtain: iC ( av ) =
=
⋅ = I L ⋅ π ⋅ 2VP / Vr
=
∆t
2Vr
2Vr R
2π f
iD ( av ) = iC ( av ) + I L = I L ⎡⎣1 + π 2VP / Vr ⎤⎦
VP
(3.31)
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(4) Dertermine the peak value of the diode current , iD (max)
iD (max)
dvI
=C
+ iL
dt
dvI
d
(t = t1 = −∆t ) ⇒ C
= C (VP cos(−ω∆t ) ) = ωCVP sin(ω∆t )
dt
dt
(ω∆t )3
+
= ω ⋅ C ⋅ VP ⋅ (ω∆t )
[sin(ω∆t )] = ω∆t +
3!
2Vr
VP
= 2πf ⋅
⋅ VP ⋅
= I L ⋅ 2π ⋅ 2VP / Vr
fVr R
VP
iD (max) = iC + I L = I L ⎣⎡1 + 2π 2VP / Vr ⎦⎤
S. C. Lin, EE National Chin-Yi University of Technology
(3.32)
51
the full-wave rectifier circuit.
∵ f r = 2 fi
VP − Vr = VP e
−T / 2
RC
VP
T /2
=
Vr = VP
RC 2 fRC
VP
Vr ( rms ) =
4 3 fRC
(3.33)
S. C. Lin, EE National Chin-Yi University of Technology
52
2.4VP
Vr ( rms ) =
( f = 60Hz, RL = kΩ, C = µF )
RC
when the ripple small then 6.5% ⇒ VP = VDC
2.4VDC 2.4 I DC
Vr ( rms ) =
=
RC
C
Vr ( rms ) 2.4
r% =
%
=
VDC
RC
If r % > 6.5%
V
1
⎡ 4.17 ⎤
⋅ VP
VDC = VP − Vr = VP − P = ⎢1 −
⎥
2
4 fRC ⎣
RC ⎦
iD ( av ) = iC ( av ) + I L = I L ⎡⎣1 + π VP / 2Vr ⎤⎦
(3.34)
iD (max) = iC + I L = I L ⎡⎣1 + 2π VP / 2Vr ⎤⎦
(3.35)
S. C. Lin, EE National Chin-Yi University of Technology
53
Figure 3.27 The “superdiode” precision half-wave rectifier and its
almost-ideal transfer characteristic. Note that when vI > 0 and the
diode conducts, the op amp supplies the load current, and the
source is conveniently buffered, an added advantage. Not shown
are the op-amp power supplies.
S. C. Lin, EE National Chin-Yi University of Technology
54
3.6 limiting and clamping circuits
3.6.1 limiter circuit.
L−
L+
≤ vI ≤
K
K
vO = KvI
Ingeneral K >1
In this section have K ≤1
L+
(a ) If vI > (the upper threshold),
K
the vO is limited or clamping to the upper limiting level L+
L−
(b) If vI < (the lower limited threshold),
K
the vO is limited to the lower limiting level L− .
S. C. Lin, EE National Chin-Yi University of Technology
55
Hard limiting.
Soft limiting.
S. C. Lin, EE National Chin-Yi University of Technology
56
S. C. Lin, EE National Chin-Yi University of Technology
57
Example.3.26 Assuming the diode to be ideal, describe the transfer
characteristic of the circuit shown in Figure E3.26.
(2) − 5V ≤ vI ≤ 5V,
both diode are cut-off and
vO = vI
Figure E3.26
Sol:
(1) vI ≤ −5V,
D1 : conducts, D2 cut-off
10
10
vO = vI
−5
10 + 10 10 + 10
= 0.5vI − 2.5
(3) vI ≥ 5V,
D1 : cut-off, D2 conducts
10
10
vO = vI
+5
10 + 10 10 + 10
= 0.5vI + 2.5
S. C. Lin, EE National Chin-Yi University of Technology
58
.
vo
vO = 0.5vI + 2.5
vI
vO = 0.5vI − 2.5
S. C. Lin, EE National Chin-Yi University of Technology
59
Example : Assuming the diode to be ideal, describe the transfer
characteristic of the circuit shown in Fig.a. 0 < vi ≤ 150V
A
D2
100kΩ
vi
(1)For 0 <Vi ≤ 25V,
200kΩ
D1
+
+
−
−
vo
both diodes are cut-off
vO = 25V
(2)For 25V<Vi < 137.5V,
D1 conducts and D2 cut-off
Sol:
For VA ≥ 100V,
both diodes are conducts
2 25
vi ⋅ +
= 100 ⇒ vi = 137.5V
3 3
vO = VA =
2
25
vI + (V)
3
3
(3)For 137.5V< Vi < 150V,
both diodes are conducts
vO = 100V
S. C. Lin, EE National Chin-Yi University of Technology
60
vo
vO =
2
25
vi +
3
3
2
3
vi
S. C. Lin, EE National Chin-Yi University of Technology
61
3.6.2 The Clamped Capacitor or DC Restorer
Figure 3.32 The clamped capacitor or dc restorer with a
square-wave input and no load.
S. C. Lin, EE National Chin-Yi University of Technology
62
Figure 3.33 The clamped capacitor with a load resistance R.
S. C. Lin, EE National Chin-Yi University of Technology
63
3.6.3 Voltage Doubler
Figure 3.34 Voltage doubler: (a) circuit; (b) waveform of the
voltage across D1.
S. C. Lin, EE National Chin-Yi University of Technology
64
S. C. Lin, EE National Chin-Yi University of Technology
65

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