Transcript from υ I

PowerPoint Overheads for
Sedra/Smith
Microelectronic Circuits 5/e
©2004 Oxford University Press.
 Microelectronics refers to the integrated circuit (IC) technology.
producing circuits that contains millions components in a silicon chip (100 mm2).
Ex) microprocessor
 In this semester, we shall study
- electronics that can be
used singly (in the design of discrete circuits)
as components of an integrated-circuit (IC) chip.
- the design and analysis of interconnection of these devices.
- available IC chips and their applications in the design of electronic system.
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Part I
Devices and Basic Circuits
The most fundamental and essential topics for the study of electronic circuits.
Chap. 1: Introduction to Electronics
Chap. 2: Operational Amplifier*
Chap. 3: Diode
Chap. 4: MOS Field-Effect Transistors (MOSFETs)
Chap. 5: Bipolar Junction Transistor (BJTs)
* Op amp is, strictly speaking, not an basic electronic device.
Op amp’s internal circuit is complex (20 or more transistors).
Why we should study the op amps here?
Op amp is commercially available as an integrated circuit (IC) package.
Op amp has well-defined terminal characteristics.
?
3
 Op amp has well-defined terminal characteristics.
1. The input impedance of an ideal op amp is supposed to be infinite.
Vi 
i=0
Ro
V’i
Ri
Op amp
Ri
Vi
RO  Ri
When Ri  
V’i =Vi regardless
of Ro.
2. The output impedance of an ideal op amp is supposed to be zero.
Vo
Op amp
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V’o
RL
V’o =Vo
regardless of RL.
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Introduction to Electronics
 The purpose of this chapter
To introduce some basic concept and terminology.
Signals
Signal amplification
Models for linear amplifier
Digital logic inverters
Circuit simulation using SPICE
5
1.1 Signals
Transducer
Information
Electrical Signal
Microphone, camera
speaker, monitor, printer
Two representations of
a signal source
the Thévenin form, Rs is low.
the Norton form , Rs is high.
 s ( t )  Rs is ( t )
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1.2 frequency spectrum of signals
 a ( t )  Va sin  t
(1.1)
Sine-wave voltage signal
amplitude Va
frequency f = 1/T Hz.
angular frequency ω = 2πf rad/s.
rms (root-mean-square, effective) value of ac value
A dc value that delivers the same time average power as the ac value does.
Va sin  t :
2
Vrms
1

R
T
Vrms  ?

T
0
Va sin  t  dt
2
R
Vrms
1

T
0 Va sin  t 
T
2
dt
Vrms  Va / 2
Fourier transform
Time domain
Frequency domain
Inverse Fourier
transform
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Spectrum of electromagnetic waves.
Old
New
Frequency Ranges (GHz)
Ka
K
26.5-40
K
K
20-26.5
K
J
18-20
Ku
J
12.4-18
X
J
10-12.4
X
I
8-10
C
H
6-8
C
G
4-6
S
F
3-4
S
E
2-3
L
D
1-2
UHF
C
0.5-1
Band Designations for Microwave
Frequency Ranges
Cell phones
800MHz, 1.8 GHz
Satellite TV
3 .7 - 4.2GHz (USA)
무궁화 : 상향 14.5448-14.73628 GHz
하향 11.7466-11.93846 GHz
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Periodic signal
Time domain
t) 
4V
1
1
(sin 0 t  sin 30 t  sin 50 t  )

3
5
(1.2)
ω0=2π/T : fundamental frequency
Frequency domain
Frequency spectrum
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Non-periodic signal
Time domain
Frequency domain
Frequency spectrum
Figure 1.6 The frequency spectrum of an arbitrary waveform such as that in Fig. 1.2.
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Frequencies of Some Common Signals
•
•
•
•
•
•
•
•
Audible sounds
20 Hz - 20 KHz
Baseband TV
0 - 4.5 MHz
FM Radio
88 - 108 MHz
Television (Channels 2-6)
54 - 88 MHz
Television (Channels 7-13)
174 - 216 MHz
Maritime and Govt. Comm.
216 - 450 MHz
Cell phones
800 MHz, 1.8 GHz
Satellite TV
3.7 - 4.2GHz (USA)
무궁화 : 상향 14.5448-14.73628 GHz
하향 11.7466-11.93846 GHz
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1.3 Analog and digital signals
Analog signal
Sampling
180 mV
Discrete-time signal
Quantization
180=(10110100)
Discretization
digitization
Digital signal
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N binary digits
N bits
Figure 1.9 Block-diagram representation of the analog-to-digital converter (ADC).
D  b0 20  b1 21  b2 22      bN 1 2 N 1
(1.3)
b0: the least significant bit (LSB), bN-1: the most significant bit (MSB),
Increasing the number of bits reduces the quantization error and
increases the resolution of the ADC.
ADC, DAC : Chapter 9.
Although the digital processing of signals is at present all-pervasive, there
remain many signal processing functions that are best performed by
analog circuits.
A good electronic engineer must proficient in the design of both
analog and digital circuits, or mixed-signal or mixed-mode design
as its currently known.
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1.4 Amplifiers
Notational Conventions
• Total signal = DC bias + time varying signal (ac)
iT  I DC  isig
T  VDC  sig
• Resistance and conductance - R and G with same
subscripts will denote reciprocal quantities. Most
convenient form will be used within expressions.
1
Gx 
Rx
and
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g 
r
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1.4.1 Signal Amplification
1.4.2 Amplifier Circuit Model
Liner amplifier
 0 ( t )  A i (t ) (1.4)
A: gain
Nonliner amplifier
 0 ( t )  A0 i ( t )  A1 i 2 ( t )  .....
- There will be distortion in output.
- There will be harmonics (2f 0 , 3 f 0 ...).
- All amplifiers are nonlinear,
but An ( n  0) are very small,
or used in linear range.
Preamplifier: high voltage gain
Power Amplifier:
modest amount of voltage gain
substantial current gain
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Figure 1.10 (a) Circuit symbol for amplifier.
(b) An amplifier with a common terminal
(ground) between the input and output ports.
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1.4.3 Voltage Gain
Voltage gain (A ) 

I
(1.5)
1.4.4 Power Gain and Current Gain
Power gain (A p ) 

load power (PL )
input power (PI )
(1.6) Transfer characteristic of a linear voltage
 0 i0
 I iI
(1.7)
Current gain (Ai ) 
Ap  A A i
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i0
iI
amplifier with voltage gain Av.
(1.8)
(1.9)
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(Decibels are only for power !)
1.4.5 Expressing Gain in Decibels
Power gain in decibels = 10 log Ap dB
 PL 
= 10 log   dB
 PI 
 O2  I2 
= 10 log 

 dB
 RL RI 
 O 
= 20 log 
if RL=RI ,


 I 
Voltage gain in decibels = 20 log A
Current gain in decibels = 20 log Ai
dB
dB
dB
A =-1 means that there is 180o phase difference between input and output signal.
Voltage gain of -20 dB is in fact attenuating the input signal
by a factor of 10 (i.e., A  0.1V / V ).
Power gain of -3 dB is in fact attenuating the input signal
by a factor of 2 (i.e., PL  PI / 2).
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1.4.6 The Amplifier Power Supplies
Amplifiers can not generate power or energy.
Power for amplification should be supplied by dc power supply (voltage
regulator) or battery.
Some amps use only one
power supply.
Figure 1.12 An amplifier that requires two dc supplies (shown as batteries) for operation.
Energy conservation Pdc  V1 I1  V2 I 2 ,
Amplifier efficiency
 
PL
 100
Pdc
Pdc  PI  PL  Pdissipated
( Pdc
PI )
(1.10)
The power efficiency is an important performance parameter for amplifiers
that handles large amount of power. (power amp as output amplifiers of stereo
systems, amps in cell phones even though the power is low.)
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EXAMPLE 1.1
• ±10 V power supplies, 1 V peak sinusoidal input, 0.1 mA peak sinusoidal
input current, 9 V peak sinusoidal output, 1 kΩ load, 9.5 mA from each power
supplies.
Find the voltage gain, the current gain, the power gain, the power drawn
from the dc power supplies, the power dissipated in the amplifier, and the
amplifier efficiency.
9

9V
 9V/V
A  20 log9  19.1 dB
I
 9mA
0 
1
1k

I
9
Ai  20 log90  39.1 dB
A i  0 
= 90 A/A
0.1
Ii
9 9
1 0.1
PL  V0rms I 0rms 
= 40.5 mW
PI  Virms I irms 
= 0.05 mW
2 2
2 2
PL
40.5
Ap 

 810 W/W A p  10 log810  29.1 dB　PI
0.05
A 
Pdissipated  Pdc + Pi - PL
Pdc  10  9.5 + 10  9.5 = 190 mW
P
  L  100 = 21.3 %
Pdc
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= 190 + 0.05 - 40.5 = 149.6 mW
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1.4.7 Amplifier Saturation
Practically speaking, the amplifier transfer
characteristic remains linear over only a
limited range of input and output voltages.
L
A
 I 
L
A
1.4.8 Nonlinear Transfer Characteristics
and Biasing
In practical amplifiers the transfer
characteristic may exhibit nonlinearity
other than output saturation.
Figure 1.13 An amplifier transfer characteristic that
is linear except for output saturation.
* Let’s consider an amplifier that is
operated from a single positive power.
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dc bias point
= Quiescent point
O ( t )  VO  o ( t )
A =
d O
d I
slope
at Q
When the input signal is sufficiently small,
 o ( t )  A i ( t ) : linear amplification
VI
 I ( t )  VI   i ( t )
Small signal approximation
Otherwise, distortion in
output signal!
Figure 1.14 (a) An amplifier transfer characteristic that shows considerable nonlinearity. (b) To obtain linear operation the amplifier is biased as shown,
and the signal amplitude is kept small. Observe that this amplifier is operated from a single power supply, VDD.
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EXAMPLE 1.2 p21
Transfer characteristic of a transistor amplifier
 O = 10 - 10-11e 40
for  I  0 V,    0.3 V

(1.11)
(a) Find L_ and L+ and corresponding υI .
(b) Find dc bias voltage VI and voltage gain for VO=5 V.
Solution
(a ) L  0.3 V
solving (1-11) for  O = 0.3 V,
  = 0.690 V
for  I  0 V,
L = 10 - 10-11
10 V
(b) solving (1.11) for  O =5 V,
Figure 1.15 A sketch of the transfer characteristic of the amplifier of
Example 1.2. Note that this amplifier is inverting (i.e., with a gain that is
negative).
VI = 0.673 V
dO / d I at  I  0.637V , A  - 200 V/V
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1.5 Circuit Models for Amplifiers
1.5.1 Voltage Amplifiers (voltage input-voltage output)
Figure 1.17 (a) Circuit model for the voltage amplifier. (b) The voltage amplifier with input signal source and load .
dependent source: Voltage controlled voltage source
o  A o i
Open  circuit voltage
 o  A o i
A o : Open  circuit voltage gain
i   s
Ri
Ri  Rs
(1.13)
Ideal voltage amplifier: Ri  
RL
RL  R
o
RL
 A o
i
RL  Ro
Ideal voltage amplifier: Ro  0
A 
Overall voltage gain:
(1.12)
o
Ri
RL
 A o
s
Ri  Rs RL  R0
When a source resistance is much greater than the load resistance (e.g., sensors),one requires
a buffer amplifier (very high input resistance, very low output resistance, overall voltage gain
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1.5.2 Cascaded Amplifiers
EXAMPLE 1.3
Figure 1.18 Three-stage amplifier for Example 1.3.
 
1 M

 0.909 V/V
 s 1 M  100 k

100 k
A   i 2  10
 9.9 V/V
i1
100 k  1 k
i 3
10 k
 100
 90.9 V/V
i 2
10 k  1 k

100 
A 3  L  1
 0.909 V/V
i 3
100   10 
A 2 

A  L  A A 2 A 3  818 V/V
i1
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 L  L  i 1


 A i 1
 s  i 1  s
 s
= 818  0.909 = 743.6 V/V
i
 100
A i  0  L
ii  i 1 1 M
= 104  A   8.18  106 A/A
P
 i
A p  L  L 0
PI  i 1ii
= A  A i  818  8.18  106 =66.9  108 W/W
Ap (dB) =
1
A (dB) + Ai (dB)
2 
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1.5.3 Other Amplifier Types
Can be measured with short-circuit.
(current source)
= Transimpedance
Amplifier
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1.5.4 Relationships between the Four Amplifier Models
Although for a given amplifier a particular one of the four models in Table 1.1 is most preferable,
any of the four can be used to model the amplifier.
Simple relationships can be derived to relate the parameters of the various models.
R 
A  A is  o 
 Ri 
A  Gis Ro
A 
(1.14)
(1.15)
Rm
Ri
(1.16)
 Ri can be determined by applying an input voltage  i
and measuring (or calculating) the input current ii .
Ri   i / ii
 Ro can be found as the ratio of the open-circuit output voltage
to the short-circuit output current.
 Or, Ro can be found by eliminating the input source (ii  0, i  0) and applying a voltage signal  x
to the output of the amplifier. If we denote the current drawn from  x into the output terminals i x ,
( i x is opposite in direction to io )
Ro   x / i x
These techniques are conceptually right, in actual practice more refined methods
are employed in measuring Ri and Ro.
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The amplifiers considered so far are unilateral; that is, signal flow is in unidirectional,
from input to output.
Most real amplifiers show some reverse transmission, which is usually undesirable but
must nonetheless be modeled.
We shall not pursue this further at this point.
Complete models for linear two port networks : Appendix B.
Chapters 4 and 5 for high frequency models.
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EXAMPLE 1.4 Models for
Bipolar Junction Transistor
(BJT, Chap.5), p29
The Heart of Model
Transconductance Amplifier represented by
Input resistance: r
Base, Emitter, Collector
Figure 1.19 (a) Small-signal circuit model for a
bipolar junction transistor (BJT).
Short-circuit transconductance: gm
Output resistance: ro
(b) The BJT connected as an amplifier with the emitter as a common
terminal between input and output (called a common-emitter amplifier).
(a ) Find an expression for  o /  s
(b) Find an expression for 
(c) An alternative small-signal circuit model for the BJT.
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be  s
r
r  Rs
o   gmbe (RL
(b) The BJT connected as an amplifier with the emitter as a common
terminal between input and output (called a common-emitter amplifier).
Neglecting the effect of ro ,
o
s

(1.17)
ro )
(1.18)
o
r
   gm (RL ro )
s
r  Rs
o
2.5

 40  ( 5 100 )
s
2.5  5
(1.19)
=  63.5 V/V
2.5
 40  5 =  66.7 V/V
2.5  5
 ib = gmbe
 = gm r
 = 40 mA/V  2.5 k
= 100 A/A
(c) An alternative small-signal circuit model for the BJT.
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1.6 Frequency Response of Amplifiers
The input signal can be expressed as the sum of sinusoidal signals of different frequencies.
1.6.1 Measuring the Amplifier Frequency Response
The resulting output is sinusoidal with the same
frequency as the input.
Transfer fuction T ( ) 
Vo
Vi
T ( )  
1.6.2 Amplifier Bandwidth
dB
3 dB
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1.6.3 Evaluating the Frequency Response
How to find the expression, or equation of transfer fuction T ( )?
L  j L getting bigger as  increases.
C  1 / j C getting smaller as  increases.
Transfer fuction: T ( ) 
Vo ( )
Vi ( )
Laplace
Transform
L  sL
C  1 / sC
Transfer function: T ( s ) 
Vo ( s )
Vi ( s )
(s: complex frequency)
1.6.4 Single-Time-Constant (STC) Networks
Single-Time-Constant (STC) Network :
a circuit that is composed of, or can be reduced to, one reactive component
(inductance or capacitance) and one resistance
Appendix D
Responses of STC network to sinusoidal, step, and pulse inputs.
You should read, if you want to be a good engineer.
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Figure 1.22 Two examples of STC networks: (a) a low-pass network and (b) a high-pass network.
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Single-Time-Constant (STC) Networks

1/ sC
T ( )  ?
1 / sC
R  1 / sC
1

V
1  sRC i
Vo  Vi

K
V
1  ( s / 0 ) i
K
1  ( / 0 )2
Im
Im
 / 0
K
(0  1/ RC  1/  )
Re
T ( j ) 
V
K
T ( s)  o 
Vi 1  ( s / 0 )
T ( j ) 
K
K
1  j ( / 0 ) 1  j( /  0 )
T ( ) 
Vo
K

Vi 1  j( / 0 )
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Re
K 0
1  ( / 0 )2  tan 1 ( / 0 )
Ke j 0

  tan 1 ( / 0 )
1  ( / 0 )2 e j ( )


T ( )   tan 1 ( / 0 )
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Frequency Response Plot (Bode Plot) of STC network of Low-Pass Filter
1 / j C
T ( ) 
K
1  ( / 0 )2
T ( )   tan 1 ( / 0 )
0 : 3-dB frequency
Corner frequency
Break frequency
Figure 1.23 (a) Magnitude and (b) phase response of STC networks of the low-pass type.
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Frequency Response Plot (Bode Plot) of STC network of High-Pass Filter
1 / j C
T ( ) 
K
1  (0 /  )2
T ( )  tan 1 (0 /  )
0 : 3-dB frequency
Corner frequency
Break frequency
Figure 1.24 (a) Magnitude and (b) phase response of STC networks of the high-pass type.
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EXAMPLE 1.5, p36
Frequency response of Voltage Amplifier
Vo
1
1
1



Vi
1  ( Rs / Ri ) 1  ( Ro / RL ) 1  sCi [( Rs Ri ) /( Rs  Ri )]
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1.6.4 Classification of Amplifiers Based on Frequency Response
(a) a capacitively coupled
amplifier
Ex) Audio Amplifier
(b) a direct-coupled
amplifier
The falloff of gain
at high frequency
The falloff of gain
at low frequency
(c) a tuned or bandpass
amplifier.
Internal capacitance Ci (previous slide)
Coupling capacitance
• Used to connect one amplifier to another
• to simplify the design process of different amplifier
• Quite large ( a fraction of μF ~a few tens of μF )
– very small reactance, but large at low frequency → voltage drop
High-pass STC
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• Some applications require gain at low frequency down to dc.
• Monolithic IC technology does not allow the fabrication of
large coupling capacitors.
• IC amplifiers are usually designed as directly coupled or dc
amplifiers.
• low-pass amplifier, low-pass filter
(b) a direct-coupled
amplifier
• Tuners for channel selection need gain only around center
frequency.
• Tuned amplifier, bandpass amplifier, bandpass filter.
(c) a tuned or bandpass
amplifier.
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1.7 Digital Logic Inverters – the most basic element in digital circuit design
1.7.1 Function of the Inverter
υI
υO
1
0 (≈ 0 V)
0
1 (≈ VDD)
Figure 1.28 A logic inverter
operating from a dc supply VDD.
1.7.2 The Voltage Transfer Characteristic (VTC)
Figure 1.15 A sketch of the transfer characteristic of the amplifier of
Example 1.2. Note that this amplifier is inverting (i.e., with a gain that is
negative). p21
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• Signal amplifiers operate in the liner rage of
transfer curve.
• Digital application use of the gross nonlinearity exhibited by the VTC.
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VIL : the maximum input value that υI can have while being
interpreted by the inverter as represented as logic 0.
VIH : the minimum input value that υI can have while being
interpreted by the inverter as represented as logic 1.
VOL : Output low level
VOH : Output high level
Transition region
1.7.3 Noise Margin
- Great advantage of digital circuit over analog circuit.
- Restoring the signal levels to standard level (VOL and VOH)
when it is presented with corrupted signal level (within the
noise margin).
1.7.4 The Ideal VTC
- Maximum noise margin.
- CMOS inverter is very close to realizing the ideal VTC.
Noise Margin for High Input
NH H  VOH  VIH
(1.25)
Noise Margin for Low Input
NM L  VIL  VOL
(1.26)
NH H  NM L  VDD /2
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40
1.7.5 Inverter Implementation
Figure 1.31 (a) The simplest
implementation of a logic inverter
using a voltage-controlled switch
(b) equivalent circuit when υI
is low
FET, BJT
For BJT, when υI is high,
current flow from υI through
Ron to ground and from VDD
to ground
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(c) equivalent circuit when υI
is high. Note that the switch
is assumed to close when υI
is high.
For FET, when υI is high, no
current flow from υI through
Ron to ground.
However, when υI is high,
current flow from VDD through
R and Ron to ground.
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Figure 1.32 A more elaborate implementation
of the logic inverter utilizing two
complementary switches. This is
the basis of the CMOS (base on
FET) inverter studied in Section
4.10.
PU: pull-up switch
PD: pull-down switch
VOH = VDD
VOL = 0
No current flows.
No current flows!
Figure 1.33 Another inverter implementation utilizing a doublethrow switch to steer the constant current IEE to RC1 (when υI is
high) or RC2 (when υI is low). This is the basis of the emittercoupled logic (ECL) studied in Chapters 7 and 11.
VOL  VCC  RC I EE
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1.7.6 Power Dissipation of the (FET based) Inverter
At present, 100,000 gates or more can
be fabricated on a single IC chip.
Very-Large-Scale-Integration,
VLSI
It is very important to keep the power dissipation be minimum
for low power consumption and low temperature.
This logic circuit will
dissipate no power. Really?
υ
O
1
When υI is low, no current flows. When υI is high, the inverter
No power dissipation
dissipates approximately VDD2/R.
Static Power Dissipation.
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Dynamic Power Dissipation
An inverter switched at a frequency f Hz exhibits a
dynamic power dissipation,
2
Pdynamic  fCVDD
(1.28)
Homework!
1.7.7 Propagation Delay
Load
Capacitor!
Input
Capacitor!
As the inverter is switched,
current must flow through
the switches to charge
(and discharge) the load
capacitance!
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1. The transistors exhibit finite switching times.
2. RC time constant τ.
The output y(t) at any time t of STC network to the
step input is,
y( t )  Y  (Y  Y0 )e  t /
(1.29)
Y : final value
Y0 : value of the response immediately after t  0
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EXAMPLE 1.6
y( t )  Y  (Y  Y0 )e  t /
(1.29)
Y0+ = VOL =?
=?
Voffset = 0.1 V
Figure 1.34 (a) The inverter
circuit after the switch opens
(i.e., for t  0).
(b) Waveforms of vI and vO. Observe that the switch is
assumed to operate instantaneously. vO rises exponentially,
starting at VOL and heading toward VOH .
VOL  Voffset +
VDD  Voffset
R  Ron
Ron
5  0.1
=0.1 
0.1  0.55V
1.1
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  ( t )  5  (5  0.55)e  t /
1
  ( t PLH )  (VOH  VOL )
2
1
 (5  0.55)
2
t PLH  0.69  0.69 RC
 0.69  103  1011
 6.9 ns
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10%, 90% of (VOL-VOH)
Input pulse
of (VOL+VOH)
rise time
Output pulse
fall time
Propagation
delay
fall time
Transition High-to Low
rise time
Transition Low-to-High
Figure 1.35 Definitions of propagation delays and transition times of the logic inverter .
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1.8 Circuit Simulation Using SPICE (Simulation Program with Integrated Circuit Emphasis)
The use of computer programs to simulate the operation of electronic circuits has become an essential
in the circuit-build process before
step
and after fabrication.
• Circuit simulation enables the designer;
- To verify the design to meet specification when actual components (with their many imperfection) are used.
- To get additional insight into circuit operation.
- To fine-tune the final design prior to fabrication.
It is not a substitute for a thorough understanding of circuit operation !
It should be performed only a later stage in the design process
after a paper-and-pencil design has been done !
• PSpice is a commercial PC version of SPICE (Cadence).
• PSpice A/D : analog and digital signal
• OrCAD Capture CIS (Component Information System) : graphical interface ( referred in this book)
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