bruce mayer, pe registered electrical & mechanical engineer [email protected]
DESCRIPTION
Engineering 43. Diodes-2. Bruce Mayer, PE Registered Electrical & Mechanical Engineer [email protected]. Learning Goals. Understand the Basic Physics of Semiconductor PN Junctions which form most Diode Devices Sketch the IV Characteristics of Typical PN Junction Diodes - PowerPoint PPT PresentationTRANSCRIPT
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx1
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Bruce Mayer, PERegistered Electrical & Mechanical Engineer
Engineering 43
Diodes-2
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx2
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Learning Goals Understand the Basic Physics of
Semiconductor PN Junctions which form most Diode Devices
Sketch the IV Characteristics of Typical PN Junction Diodes
Use the Graphical LOAD-LINE method to determine the “Operating Point” of Nonlinear (includes Diodes) Circuits
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx3
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Learning Goals Analyze diode-containing Voltage-
Regulation Circuits Use various math models for Diode
operation to solve for Diode-containing Circuit Voltages and/or Currents
Learn The difference between LARGE-signal and SMALL-Signal Circuit Models
IDEAL and PieceWise-Linear Models
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx4
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Diode Models LoadLine Analysis
works well when the ckt connected to a SINGLE Diode can be “Thevenized”
However, for NONLinear ckts, such as those containing multiple diodes, construction of the LOAD-Curve Eqn may be difficult, or even impossible.
Many such ckts can be analyzed by Idealizing the diode
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx5
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Diode Models Consider an Electrical Diode
→ We can MODEL the V-I Behavior of this Device in Several ways
V
I
REALBehavior
IDEALModel
OFFSETModel
LINEARModel
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx6
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Ideal Model (Ideal Rectifier) Analyze Ckts containing Ideal Diodes1. Assume (or Guess) a “state” for each
diode. Ideal Diodes have Two states1. ON → a SHORT Ckt when Fwd Biased2. OFF →an OPEN Ckt if Reverse Biased
2. Check the Assumed Opens & Shorts• Should have Current thru the SHORTS• Should have ∆V across the OPENS
Dio
de O
N
Diode OFF
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx7
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Ideal Model (Ideal Rectifier)3. Check to see if guesses for i-flow, ∆V,
and BIAS-State are consistent with the Ideal-Diode Model
4. If i-flow, ∆V, and bias-V are consistent with the ideal model, then We’re DONE.• If we arrive at even a SINGLE
Inconsistency, then START OVER at step-1
Dio
de O
N
Diode OFF
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx8
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode Find For Ckt Below find:• Use the
IdealDiodeModel
od VI &1
1dI
2dI
A
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx9
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode
Assume BOTH Diodes are ON or Conducting
In this Case VD1 = VD2 = 0
Thus D2 Anode is connected to GND
Then Find by Ohm
Next use KCL at Node-A (in = out)
1dI
2dI
mA 1k 10
V 0102
dI
A
k 9.9V 100
21 dd II
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx10
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode
Using ID2 = 1 mA
Thus Now must Check
that both Diodes are indeed conducting
From the analysis
Thus the current thru both Diodes is positive which is consistent with the assumption
1dI
2dI
A
mA 1k 9.9
V 1001
dI
mA 0101.01 dI
mA 1µA 10 21 dd II
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx11
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode
Since both Diodes conduct the Top of Vo is connected to GND thru D2 & D1
Another way to think about this is that since VD2 = 0 and VD1 = 0 (by Short Assumption) Find Vo = GND+VD2+VD1
= GND + 0 + 0 = 0 Thus the Answer
1dI
2dI
A
V 0µA 101 od VI
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx12
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode Find For Ckt Below find:• Use the
IdealDiodeModel• Note the
differentvalues onR1 & R2–Swapped
od VI &1
1dI
2dI
B
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx13
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode
Again Assume BOTH Diodes are ON, or Conducting
As Before VD1 = VD2 = 0
Again VB shorted to GND thru D1
Then Find by Ohm
Now use KCL at Node-B (in = out)
mA 01.1k 9.9
V 0102
dI
k 01V 100
21 dd II
1dI
2dI
B
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx14
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode
Using ID2 = 1.01 mA
Thus Now must Check
that both Diodes are indeed conducting
From the analysis
We find and INCONSISTENCY and our Assumption is WRONG
1dI
2dI
B
mA 01.1k 01
V 1001
dI
mA 01.01 dI
mA 01.1µA 10 21 dd II
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx15
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode
Must Iterate Assume • D1 → OFF
D2 → ON
In this Case D1 is an OPEN → ID1 =0
Current ID2 must flow thru BOTH Resistors
Then Find by Ohm
mA 005.1
k 9.910V 1010
2
dI
1dI
2dI
B
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx16
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode
Must Check that D1 is REVERSE Biased as it is assumed OFF
By KVL & Ohm
Thus D1 is INDEED Reverse-Biased, Thus the Ckt operation is Consistent with our Assumption
1dI
2dI
B
mV 50 V 05.0mA005.1kΩ10V10
B
B
VV
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx17
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example Ideal Diode
Calculate Vo by noting that:
D2 is ON → VD2 = 0D1 is OFF → Current can only flow thru D2
In this case Vo = VB
By the Previous Calculation, Find
1dI
2dI
B
mV 50A 01 od VI
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx18
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Offset & Linear Models The Offset Model
Better than Ideal, but no account of Forward-Slope
The Linear Model
The model eqn:
Yet moreaccurate, but also does not account for Rev-Bias Brk-Down
V6.0 DbD iRv
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx19
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Point Slope Line Eqn When constructing
multipiece-wise linear models, the Point-Slope Equation is extremely Useful
• Where
– (x1, y1) & (x2, y2) are KNOWN Points
Example: Find Eqn for line-segment:
2 4 6 8 10 12 14 16 18 204
6
8
10
12
14
16
18
x
y
11 xxmyy
12
12
xxyy
xym
(3,17)
(19,5)
43
1612
319175
m
xym
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx20
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Point Slope Line Eqn Using the 2nd Point
Can easily convert to y = mx+b
Multiply by m, move −5 to other side of =
2 4 6 8 10 12 14 16 18 204
6
8
10
12
14
16
18
x
y
19435 xy
(3,17)
(19,5)
477
43
420
457
43
54
5743
457
435
19435
xy
xy
xy
xy
xy
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx21
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Slopes on vi Curve With Reference to
the Point-Slope eqn v takes over for x, and i takes over for y
The Slope on a vi Curve is a conductance
If the curve is NONlinear then the local conductance is the first Derivative
Recall the Op-Pt is also the Q-Pt
GmVIm
vi
vi
iemens SVolt
Amps
gdvdim
dvdim
OpOpvi
OpOpvi
,
, SiemensVolt
Amps
gdvdimm
QQviOpvi ,,
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx22
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Slopes on vi Curve Finally recall that
conductance & resistance are Inverses
Example: Find the RESISTANCE of the device associated with the VI curve that follows
2 4 6 8 10 12 14 16 18 204
6
8
10
12
14
16
18
V (volts)
I (am
ps)
Linear VI Curve
RGmvi
1
Siemens 43
V16A12
Volts319Amps517
Gm
VIm
vi
vi
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx23
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Slopes on vi Curve Since R = 1/G Find
the Device Resistance as
For a NONlinear vi curve the local slope then: r = 1/g
The General Reln2 4 6 8 10 12 14 16 18 20
4
6
8
10
12
14
16
18
V (volts)
I (am
ps)
Linear VI Curve
S 0.751
RGmvi
1.333 1 Rmvi
Ohms 34
A12V16
Amps517Volts319
R
IVR
OpOp
Op
Op
didvr
didvr
dvdig
r
elyalternativor 11
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx24
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example PieceWise Linear Model Construct a
PieceWise Linear Model for the Zener vi curve shown at Right
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx25
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
PieceWise Linear Zener
m for Segment A
Us Pt-Slp eqn with (0.6V,0mA) for Pt-1
Segment- B is easy
101mS 100
V0.61.6mA01001
A
AA
m
VI
Rm
mA60mS100 :OR
V6.0mS1000
DD
DD
vivi
0Di
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx26
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
PieceWise Linear Zener
m for Segment C
Us Pt-Slp eqn with (−6V,0mA) for Pt-1
Thus the PieceWise Model for the Zener
121mS 33.83
1.2VmA100
V2.76mA10001
C
CC
m
VI
Rm
mA500mS3.83 :OR
V6mS3.830
DD
DD
vivi
V6ifmA5003.3mS8V6.0V6if0
V6.0ifmA60mS100
DD
D
DD
D
vvv
vvi
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx27
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example PieceWise Linear Model Alternatively in
terms of Resistances
ADVICE: remember the Pt-Slope Line-Eqn
V6ifmA50012
V6.0V6if0
V6.0ifmA6010
DD
D
DD
D
vvv
vv
i
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx28
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Half-Wave Rectifier Ckt Consider an Sinusoidal V-Source, such
as an AC socket in your house, supplying power to a Load thru a Diode
Power Input Load Voltage
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx29
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
HalfWave Rectifier Note that the Doide
is FWD-Biased during only the POSITIVE half-cycle of the Source
Using this simple ckt provides to the load ONLY positive-V; a good thing sometimes
However, the positive voltage comes in nasty PULSES which are not well tolerated by positive-V needing loads
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx30
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Smoothed HalfWave Rectifier Adding a Cap to the
Circuit creates a Smoothing effect
In this case the Diode Conducts ONLY when vs>vC and vC=vL
This produces vL(t) and iL(t) curves
Note that iL(t) is approx. constant
LCD
LC
iiidtdvCi
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx31
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Smoothed HalfWave Rectifier The change in
Voltage across the Cap is called “Ripple”
Often times the load has a Ripple “Limit” from which we determine Cap size
From the iL(t) curve on the previous slide note:• Cap Discharges for
Almost the ENTIRE Cycle time, T (diode Off)
• The Load Current is approx. constant, IL
Recall from EARLY in the Class
Ripple
TIQ :lysymbolical Or,
Time Current Charge
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx32
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Smoothed HalfWave Rectifier Also from Cap
Physics (chp3)
In the Smoother Ckt the Cap charges during the “Ripple” portion of the curve
Equating the Charge & Discharge “Q’s find
Note that both these equations are Approximate, but they are still useful for initial Ckt Design
Solving the equations for the Cap Value needed for a given Vr
capcap VCQ
TIVCQ Lrcap Charge Discharge
r
L
VTIC
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx33
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Smoothed HalfWave Rectifier Find the Approximate Average Load
Voltage
22,,
,r
mloLhiL
mavgLVV
VVVV
avgLV ,
VL,hiVL,lo
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx34
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Capacitor-Size Effect Any load will discharge the
capacitor. In this case, the output will depend on how the RC time constant compares with the period of the input signal.
The plots at right consider the various cases for the simple circuit above with a 1kHz, 5V sinusoidal input
mS 1 TRC
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx35
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Full Wave Rectifier The half-wave ckt
will take an AC-Voltage and convert it to DC, but the rectified signal has gaps in it.
The gaps can be eliminated thru the use of a Full-Wave rectifier ckt
The Diodes are• Face-to-Face (right)• Butt-to-Butt (left)
Thisrectifiedoutput hasNO Gaps
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx36
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Full Wave Rectifier Operation
D1 Supplies V to Load
D4 Supplies V to Load
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx37
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Full Wave Rectifier Smoothing The Ripple on the
FULL wave Ckt is about 50% of that for the half-wave ckt
Since the Cap DIScharges only a half-period compared to the half-wave ckt, the size of the “smoothing” cap is then also halved:
r
L
VTIC
2
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx38
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Small Signal Models Often we use NonLinear Circuits to
Amplify, or otherwise modify, non-steady Signals such as ac-sinusoids that are small compared to the DC Operating Point, or Q-Point of the Circuit.
Over a small v or i range even NonLinear devices appear linear. This allows us to construct a so-called small signal Linear Model
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx39
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Small Signal Analysis Small signal Analysis is usually done in
Two Parts:1. Large-Signal DC Operating Point (Q-Pt)2. Linearize about the Q-Pt using calculus
Recall from Calculus
This approximation become more accrate as ∆y & ∆x become smaller
xy
dxdy
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx40
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Small Signal Analsyis Now let y→iD, and x→ vD
Use a DC power Supply to set the operating point on the diode curve as shown at right• This could be done using LoadLine methods
From Calculus
Next Take derivative about the Q-Pt Siemensor A/V of units DDDD vidvdi
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx41
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Small Signal Analysis About Q-Pt
Now if we have a math model for the vi curve, and we inject ON TOP of VDQ a small signal, ∆vD find
The derivative is the diode small-signal Conductance at Q
Qnear D
D
QD
D
vi
dvdi
DdDQD
DD vgv
dvdii
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx42
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Small Signal Analysis In the large signal
Case: R = 1/G By analogy In the
small signal case: r = 1/g Also since small
signal analysis is associated with small amounts that change with time…
Define the Diode’s DYNAMIC, small-signal Conductance and Resistance
QD
D
QD
D
dd
QD
Dd
didv
dvdi
gr
dvdig
1
1
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx43
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Small Signal Analysis Note Units for rd
Recall the approximation for iD
Change Notation for Small Signal conditions
Find rd for a “Shockley” Diode in majority FWD-Bias
Recall Shockley Eqn
Then the Large-signal Operating Point at vD = VDQ
AmpVolt
VoltAmp 1
1
QD
Dd dv
dir
d
DD
QD
DD r
vvdvdii
dD
dD
vvii
1
T
D
nVv
sD eIi
T
DQ
T
DQ
nVV
snVV
sDQ eIeII 1
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx44
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Small Signal Analysis Taking the derivative
of the Shockely Eqn
Recall from last sld
Sub this Reln into the Derivative Eqn
Recall
Subbing for diD/dvD
T
D
T
D
nVv
STT
nVv
SQD
D eInVnV
eIdvdi 11
DQnVV
s IeI T
DQ
T
DQDQ
TQD
D
nVI
InVdv
di
1
1
QD
Dd dv
dir
DQ
T
T
DQ
QD
Dd I
nVnVI
dvdir
11
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx45
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Notation: Large, Small, Total VDQ and IDQ are the LARGE Signal
operating point (Q-Pt) DC quantities• These are STEADY-STATE values
vD and iD are the TOTAL and INSTANTANEQOUS quantities• These values are not necessarily steady-
state. To emphasize this we can write vD(t) and iD(t)
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx46
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Notation: Large, Small, Total vd and id are the SMALL, AC quantities• These values are not necessarily steady-
state. To emphasize this we can write vd(t) and id(t)
AnExamplefor DiodeCurrentnotation
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx47
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Effect of Q-Pt Location From
Analysis
DQ
Td
ddd
InVr
rvi
and
ppdi ,2
ppdi 1
ppdv 1ppdv 2
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx48
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
DC Srcs SHORTS in Small-Signal In the small-signal equivalent circuit DC
voltage-sources are represented by SHORT CIRUITS; since their voltage is CONSTANT, they exhibit ZERO INCREMENTAL, or SIGNAL, voltage
Alternative Statement: Since a DC Voltage source has an ac component of current, but NO ac VOLTAGE, the DC Voltage Source is equivalent to a SHORT circuit for ac signals
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx49
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Setting Q, Injecting v Consider this ckt with AC & DC V-srcs
Sets Q
Sets vd
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx50
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Large and Small Signal Ckts Recall from Chps 3
and 5 for Caps:• OPENS to DC• SHORTS to fast AC
Thus if C1 is LARGE it COUPLES vin(t) with the rest of the ckt
Similarly, Large C2 couples to the Load
To Find the Q-point DEcouple vin and vo to arrive at the DC circuit
CjZC 1
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx51
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Large and Small Signal Ckts Finding the Large
signal Model was easy; the Caps acts as an OPENS
The Small Signal Ckt needs more work• Any DC V-Supply is
a SHORT to GND• The Diode is
replaced by rd (or gd)• The Caps are Shorts
Thus the Small Signal ckt for the above
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx52
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example: Small Signal Gain Find the Small
Signal Amplification (Gain), Av, of the previous circuit
Using the Small Signal Circuit
Note that RC, rd, and RL are in Parallel
And vo(t) appears across this parallel combination
The equivalent ckt
LdCp RRRR1111
tvo
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx53
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Example: Small Signal Gain Thus for this Ckt the
Large, Small, and small-Equivalent ckts
Then the Amplification (Gain) by Voltage Divider
p
p
in
ov RR
RvvA
tvo
LdCp RRRR1111
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx54
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
All Done for Today
SmallSignal
BJT Amp
Common Collector Amplifier
LARGESignalModel
SMALLSignalModel
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx55
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Bruce Mayer, PERegistered Electrical & Mechanical Engineer
Engineering 43
Appendix
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx56
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
tvo
tvo
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx57
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
Small Signal Analysis In the large signal
Case: R = 1/G By analogy In the
small signal case: r = 1/g Also since small
signal analysis is associated with small amounts that change with time…
Define the Diode’s DYNAMIC Conductance and Resistance
QD
D
QD
D
dd
QD
Dd
didv
dvdi
gr
dvdig
1
1
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx58
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
P10.67 Graph vo vs. vi for vi: −5V to +5V
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
file =XY_Plot_0211.xls
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx59
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx60
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx61
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis
[email protected] • ENGR-43_Lec-10b_Diode-2_SmallSignalAnalysis.pptx62
Bruce Mayer, PE Engineering-43: Engineering Circuit Analysis