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8/9/2019 L5 CMOS Inverter Static
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Lecture-5-MOS-Inverter
Introduction
Inverter is fundamental logic gate uses single input.
Basic principles employing in design and analysis of
inverter can be directly applied on complex gates.
Therefore inverter design forms basis for digital circuits.
First we start with DC Characteristics.
What do you understand by DC response of the
circuit?
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Introduction (contd.)
The DC response is Ultra Low Frequency response of theCircuit.
When you are at a logic low or high before switching it
is a DC condition.
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Lecture-5-MOS-Inverter
Actual Inverter CharacteristicsGeneral Model of inverter
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Noise Immunity and Noise Margins
Output signal is transmitted through interconnect to next inverter.
Interconnects are prone to noise. Suppose output of 1st inverter is
perturbed, and its level is higher than VIL than it can not be correctly
predicted at output of 2nd
inverter. Thus VIL is max allowable input voltage which is low enough to ensure
1 output.
Similarly VIH is minimum allowable input voltage which is high enough
to ensure 0 output.
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Noise Immunity and Noise Margins Noise tolerance also called Noise Margins and denoted by NM. Two
noise margins will be defined : for low signal level as NML and highsignal level as NMH as
Justification for VIL and VIH
noise
in
outinout
noiseinoutinout
VdV
dVvfV
VVfVVfV
(!
(!!
)(
)();(
'
'
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Lecture-5-MOS-Inverter
CMOS INVERTER
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Region of operation:
TOPINTOPIN
TOPGSPTOPGSPDDTOPIN
DDTOPINDDTOPIN
TOPGSPTOPGSPTOPGSP
-VVV-VVV
-VVV-VVVVVV
VVVVVV
VVVVVV
"
""
"
TOUTOU
DSPDSP
PMOS
SATURATEDLINEARCUTOFF
TOnINTOnINOUT
TOnGSnTOnGSnTOnIN
TOnINTOnIN
TOnGSnTOnGSnTOnGSn
-VVV-VVV
-VVV-VVVVV
VVVV
VVVVVV
"
"
""
""
TOU
DSnDSn
NMOS
SATURATEDLINEARCUTOFF
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If KR = 1 Then
Ideal Logic threshold
value.
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Next Topic
MOS Inverter : Dynamic Characteristics