NSC LMV921 1.8v, 1mhz, low power operational amplifiers with rail-to-rail input and output Datasheet

LMV921 Single/ LMV922 Dual/ LMV924 Quad
1.8V, 1MHz, Low Power Operational Amplifiers with
Rail-To-Rail Input and Output
General Description
Features
The LMV921 Single/LMV922 Dual/LMV924 Quad are guaranteed to operate from +1.8V to +5.0V supply voltages and
have rail-to-rail input and output. This rail-to-rail operation
enables the user to make full use of the entire supply voltage
range. The input common mode voltage range extends
300mV beyond the supplies and the output can swing
rail-to-rail unloaded and within 100mV from the rail with
600Ω load at 1.8V supply. The LMV921/LMV922/LMV924
are optimized to work at 1.8V which make them ideal for portable two-cell battery-powered systems and single cell Li-Ion
systems.
The
LMV921/LMV922/LMV924
exhibit
excellent
speed-power ratio, achieving 1MHz gain bandwidth product
at 1.8V supply voltage with very low supply current. The
LMV921/LMV922/LMV924 are capable of driving 600Ω load
and up to 1000pF capacitive load with minimal ringing. The
LMV921/LMV922/LMV924’s high DC gain of 100dB makes
them suitable for low frequency applications.
The LMV921 (Single) is offered in a space saving SC70–5
and SOT23–5 packages. The SC70–5 package is only
2.0X2.1X1.0mm. These small packages are ideal solutions
for area constrained PC boards and portable electronics
such as cellphones and PDAs.
(Typical 1.8V Supply Values; Unless Otherwise Noted)
n Guaranteed 1.8V, 2.7V and 5V specifications
n Rail-to-Rail input & output swing
— w/600Ω load
100 mV from rail
— w/2kΩ load
30 mV from rail
n VCM
300mV beyond rails
n 90dB gain w/600Ω load
n Supply current
145µA/amplifier
n Gain bandwidth product
1MHz
n LMV921 Maximum VOS
6mV
n LMV921 available in Ultra Tiny, SC70-5 package
n LMV922 available in MSOP-8 package
n LMV924 available in TSSOP-14 package
Applications
n
n
n
n
n
n
n
Cordless/cellular phones
Laptops
PDAs
PCMCIA
Portable/battery-powered electronic Equipment
Supply current Monitoring
Battery monitoring
Connection Diagrams
5-Pin SC70-5/SOT23-5
8-Pin MSOP/SOIC
DS100979-84
Top View
DS100979-2
Top View
© 1999 National Semiconductor Corporation
DS100979
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LMV921 Single/ LMV922 Dual/ LMV924 Quad 1.8V, 1MHz, Low Power Operational Amplifiers with
Rail-To-Rail Input and Output
December 1999
LMV921 Single/ LMV922 Dual/ LMV924 Quad
Connection Diagrams
(Continued)
14-Pin TSSOP/SOIC
DS100979-1
Top View
Ordering Information
Package
5-Pin SC70-5
5-Pin SOT23-5
8-Pin MSOP
14-Pin TSSOP
8-Pin SOIC
14-Pin SOIC
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Temperature Range
Industrial
−40˚C to +85˚C
Packaging
Marking
Transport Media
NSC
Drawing
MAA05A
LMV921M7
A21
1k Units Tape and Reel
LMV921M7X
A21
3k Units Tape and Reel
LMV921M5
A29A
1k Units Tape and Reel
LMV921M5X
A29A
3k Units Tape and Reel
LMV922MM
LMV922
1k Units Tape and Reel
LMV922MMX
LMV922
3.5k Units Tape and Reel
LMV924MT
LMV924
Rails
LMV924MTX
LMV924
2.5k Units Tape and Reel
LMV922M
LMV922M
Rails
LMV922MX
LMV922M
2.5k Units Tape and Reel
LMV924M
LMV924M
Rails
LMV924MX
LMV924M
2.5k Units Tape and Reel
2
MA05B
MUA08A
MTC14
M08A
M14A
Operating Ratings (Note 1)
Supply Voltage
1.5V to 5.0V
−40˚C ≤ TJ ≤ 85˚C
Temperature Range
Thermal Resistance (θJA)
ESD Tolerance (Note 2)
Machine Model
100V
Human Body Model
2000V
Differential Input Voltage
± Supply Voltage
Supply Voltage (V+–V −)
5.5V
235˚C/W
155˚C/W
150˚C
SOIC Package
8-Pin Surface Mount
175˚C/W
235˚C
14-Pin Surface Mount
127˚C/W
−65˚C to 150˚C
Mounting Temp.
Infrared or Convection (20 sec)
265 ˚C/W
TSSOP Package
14-Pin Surface Mount
Output Short Circuit to V− (Note 3)
Junction Temperature (Note 4)
440 ˚C/W
Tiny SOT23-5 Package
5-Pin Surface Mount
MSOP Package
8-Pin Surface Mount
Output Short Circuit to V+ (Note 3)
Storage Temperature Range
Ultra Tiny SC70-5 Package
5-Pin Surface Mount
1.8V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 1.8V, V
RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol
VOS
Parameter
Input Offset Voltage
Condition
−
= 0V, VCM = V+/2, VO = V+/2 and
Typ
(Note 5)
Limits
(Note 6)
Units
LMV921 (Single)
−1.8
6
8
mV
max
LMV922 (Dual)
LMV924 (Quad)
−1.8
8
9.5
mV
max
TCVOS
Input Offset Voltage Average
Drift
1
IB
Input Bias Current
12
35
50
nA
max
IOS
Input Offset Current
2
25
40
nA
max
IS
Supply Current
LMV921 (Single)
145
185
205
LMV922 (Dual)
330
400
550
LMV924 (Quad)
560
700
850
0 ≤ VCM ≤ 0.6V
82
62
60
−0.2V ≤ VCM ≤ 0V
1.8V ≤ VCM ≤ 2.0V
74
50
dB
min
78
67
62
dB
min
-0.3
-0.2
0
V
max
2.15
2.0
1.8
V
min
RL = 600Ω to 0.9V,
VO = 0.2V to 1.6V, VCM = 0.5V
91
77
73
RL = 2kΩ to 0.9V,
VO = 0.2V to 1.6V, VCM = 0.5V
95
80
75
RL = 600Ω to 0.9V,
VO = 0.2V to 1.6V, VCM = 0.5V
79
65
61
RL = 2kΩ to 0.9V,
VO = 0.2V to 1.6V, VCM = 0.5V
83
68
63
CMRR
Common Mode Rejection Ratio
PSRR
Power Supply Rejection Ratio
1.8V ≤ V+ ≤ 5V,
VCM = 0.5V
VCM
Input Common-Mode Voltage
Range
For CMRR ≥ 50dB
AV
Large Signal Voltage Gain
LMV921 (Single)
Large Signal Voltage Gain
LMV922 (Dual)
LMV924 (Quad)
3
µV/˚C
µA
max
dB
min
dB
min
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
LMV921 Single/ LMV922 Dual/ LMV924 Quad
1.8V DC Electrical Characteristics
(Continued)
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 1.8V, V
RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol
Parameter
Output Swing
VO
−
= 0V, VCM = V+/2, VO = V+/2 and
Condition
Typ
(Note 5)
Limits
(Note 6)
Units
1.7
1.65
1.63
V
min
0.075
0.090
0.105
V
max
1.77
1.75
1.74
V
min
0.025
0.035
0.040
V
max
Sourcing, VO = 0V
VIN = 100mV
6
4
3.3
mA
min
Sinking, VO = 1.8V
VIN = −100mV
10
7
5
mA
min
RL = 600Ω to 0.9V
VIN = ± 100mV
RL = 2kΩ to 0.9V
VIN = ± 100mV
IO
Output Short Circuit Current
1.8V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 1.8V, V
RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol
Parameter
−
= 0V, VCM = V+/2, VO = V+/2 and
Conditions
Typ
(Note 5)
(Note 7)
Units
SR
Slew Rate
0.39
V/µs
GBW
Gain-Bandwidth Product
1
MHz
Φm
Phase Margin
60
Deg.
Gm
Gain Margin
10
dB
en
Input-Referred Voltage Noise
f = 1 kHz, VCM = 0.5V
45
in
Input-Referred Current Noise
f = 1 kHz
0.1
THD
Total Harmonic Distortion
f = 1kHz, AV = +1
RL = 600kΩ, VIN = 1 VPP
Amp-to-Amp Isolation
(Note 8)
0.089
%
140
dB
2.7V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.7V, V
RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol
VOS
Parameter
Input Offset Voltage
Condition
−
= 0V, VCM = V+/2, VO = V+/2 and
Typ
(Note 5)
Limits
(Note 6)
Units
LMV921 (Single)
−1.6
6
8
mV
max
LMV922 (Dual)
LMV924 (Quad)
−1.6
8
9.5
mV
max
TCVOS
Input Offset Voltage Average
Drift
1
IB
Input Bias Current
12
35
50
nA
max
IOS
Input Offset Current
2
25
40
nA
max
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4
µV/˚C
(Continued)
Symbol
Parameter
CMRR
Limits
(Note 6)
LMV921 (Single)
147
190
210
LMV922 (Dual)
380
450
600
LMV924 (Quad)
580
750
900
0V ≤ VCM ≤ 1.5V
84
62
60
−0.2V ≤ VCM ≤ 0V
2.7V ≤ VCM < 2.9V
73
50
dB
min
78
67
62
dB
min
-0.3
-0.2
0
V
max
3.050
2.9
2.7
V
min
RL = 600Ω to 1.35V,
VO = 0.2V to 2.5V
98
80
75
RL = 2kΩ to 1.35V,
VO = 0.2V to 2.5V
103
83
77
Large Signal Voltage Gain
LMV922 (Dual)
LMV924 (Quad)
RL = 600Ω to 1.35V,
VO = 0.2V to 2.5V
86
68
63
RL = 2kΩ to 1.35V,
VO = 0.2V to 2.5V
91
71
65
Output Swing
RL = 600Ω to 1.35V
VIN = ± 100mV
2.62
2.550
2.530
V
min
0.075
0.095
0.115
V
max
2.675
2.650
2.640
V
min
0.025
0.040
0.045
V
max
Sourcing, VO = 0V
VIN = 100mV
27
20
15
mA
min
Sinking, VO = 2.7V
VIN = −100mV
28
22
16
mA
min
Common Mode Rejection Ratio
Condition
PSRR
Power Supply Rejection Ratio
1.8V ≤ V+ ≤ 5V,
VCM = 0.5V
VCM
Input Common-Mode Voltage
Range
For CMRR ≥ 50dB
Large Signal Voltage Gain
LMV921 (Single)
AV
VO
= 0V, VCM = V+/2, VO = V+/2 and
Typ
(Note 5)
Supply Current
IS
−
RL = 2kΩ to 1.35V
VIN = ± 100mV
IO
Output Short Circuit Current
Units
uA
max
dB
min
dB
min
2.7V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.7V, V
RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol
Parameter
−
= 0V, VCM = 1.0V, VO = 1.35V and
Conditions
(Note 7)
Typ
(Note 5)
Units
SR
Slew Rate
0.41
V/µs
GBW
Gain-Bandwidth Product
1
MHz
Φm
Phase Margin
65
Deg.
Gm
Gain Margin
10
dB
en
Input-Referred Voltage Noise
f = 1 kHz, VCM = 0.5V
45
in
Input-Referred Current Noise
f = 1 kHz
0.1
5
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
2.7V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.7V, V
RL > 1 MΩ. Boldface limits apply at the temperature extremes.
LMV921 Single/ LMV922 Dual/ LMV924 Quad
2.7V AC Electrical Characteristics
(Continued)
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.7V, V
RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol
Parameter
THD
−
= 0V, VCM = 1.0V, VO = 1.35V and
Conditions
Total Harmonic Distortion
f = 1 kHz, AV = +1
RL = 600kΩ, VIN = 1 VPP
Amp-to-Amp Isolation
(Note 8)
Typ
(Note 5)
Units
0.077
%
140
dB
5V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 5V, V
RL > 1 MΩ.Boldface limits apply at the temperature extremes.
Symbol
VOS
Parameter
Input Offset Voltage
Condition
−
= 0V, VCM = V+/2, VO = V+/2 and
Typ
(Note 5)
Limits
(Note 6)
Units
LMV921 (Single)
−1.5
6
8
mV
max
LMV922 (Dual)
LMV924 (Quad)
−1.5
8
9.5
mV
max
TCVOS
Input Offset Voltage Average
Drift
1
IB
Input Bias Current
12
35
50
nA
max
IOS
Input Offset Current
2
25
40
nA
max
IS
Supply Current
LMV921 (Single)
160
210
230
LMV922 (Dual)
400
500
700
LMV924 (Quad)
750
850
980
0V ≤ VCM ≤ 3.8V
86
62
61
−0.2V ≤ VCM ≤ 0V
5.0V ≤ VCM ≤ 5.2V
72
50
dB
min
78
67
62
dB
min
-0.3
-0.2
0
V
max
5.350
5.2
5.0
V
min
RL = 600Ω to 2.5V
VO = 0.2V to 4.8V
104
86
82
RL = 2kΩ to 2.5V
VO = 0.2V to 4.8V
108
89
85
RL = 600Ω to 2.5V
VO = 0.2V to 4.8V
90
72
68
RL = 2kΩ to 2.5V
VO = 0.2V to 4.8V
96
77
73
CMRR
Common Mode Rejection Ratio
PSRR
Power Supply Rejection Ratio
1.8V ≤ V+ ≤ 5V
VCM = 0.5V
VCM
Input Common-Mode Voltage
Range
For CMRR ≥ 50dB
AV
Voltage Gain
LMV921 (Single)
Voltage Gain
LMV922 (Dual)
LMV924 (Quad)
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6
µV/˚C
µA
max
dB
min
dB
min
(Continued)
Symbol
Parameter
Output Swing
VO
−
= 0V, VCM = V+/2, VO = V+/2 and
Condition
Typ
(Note 5)
Limits
(Note 6)
Units
4.895
4.865
4.840
V
min
0.1
0.135
0.160
V
max
4.965
4.945
4.935
V
min
0.035
0.065
0.075
V
max
LMV921 Sourcing, VO = 0V
VIN = 100mV
98
85
68
LMV922, LMV924 Sourcing, VO =
0V
VIN = 100mV
60
35
mA
min
Sinking, VO = 5V
VIN = −100mV
75
65
45
mA
min
RL = 600Ω to 2.5V
VIN = ± 100mV
RL = 2kΩ to 2.5V
VIN = ± 100mV
IO
Output Short Circuit Current
5V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 5V, V
R L > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol
Parameter
−
= 0V, VCM = V+/2, VO = 2.5V and
Conditions
(Note 7)
Typ
(Note 5)
Units
SR
Slew Rate
0.45
V/µs
GBW
Gain-Bandwidth Product
1
MHz
Φm
Phase Margin
70
Deg.
Gm
Gain Margin
15
dB
en
Input-Referred Voltage Noise
f = 1 kHz, VCM = 1V
45
in
Input-Referred Current Noise
f = 1 kHz
0.1
THD
Total Harmonic Distortion
f = 1 kHz, AV = +1
RL = 600Ω, VO = 1 VPP
Amp-to-Amp Isolation
(Note 8)
0.069
%
140
dB
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.
Note 2: Human body model, 1.5 kΩ in series with 100 pF. Machine model, 200Ω in series with 100 pF.
Note 3: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the
maximum allowed junction temperature of 150˚C. Output currents in excess of 45 mA over long term may adversely affect reliability.
Note 4: The maximum power dissipation is a function of TJ(max) , θJA, and TA. The maximum allowable power dissipation at any ambient temperature is
PD = (TJ(max)–T A)/θJA. All numbers apply for packages soldered directly into a PC board.
Note 5: Typical Values represent the most likely parametric norm.
Note 6: All limits are guaranteed by testing or statistical analysis.
Note 7: V+ = 5V. Connected as voltage follower with 5V step input. Number specified is the slower of the positive and negative slew rates.
Note 8: Input referred, V+ = 5V and RL = 100kΩ connected to 2.5V. Each amp excited in turn with 1kHz to produce VO = 3VPP.
7
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
5V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 5V, V
RL > 1 MΩ.Boldface limits apply at the temperature extremes.
LMV921 Single/ LMV922 Dual/ LMV924 Quad
Simplified Schematic
DS100979-A9
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8
Supply Current vs.
Supply Voltage (LMV921)
Unless otherwise specified, VS = +5V, single supply, TA = 25˚C.
Input Bias Current
vs. VCM
DS100979-A1
Sourcing Current vs.
Output Voltage
Sourcing Current vs.
Output Voltage
DS100979-D5
Sourcing Current vs.
Output Voltage
DS100979-B8
Sinking Current vs.
Output Voltage
DS100979-B3
Sinking Current vs.
Output Voltage
DS100979-B2
Sinking Current vs.
Output Voltage
DS100979-B7
Offset Voltage vs.
Common Mode Voltage
DS100979-B1
9
DS100979-B4
DS100979-D1
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
Typical Performance Characteristics
LMV921 Single/ LMV922 Dual/ LMV924 Quad
Typical Performance Characteristics
Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
Offset Voltage vs.
Common Mode Voltage
Offset Voltage vs.
Common Mode Voltage
DS100979-C9
Output Voltage Swing vs.
Supply Voltage
DS100979-C8
Gain and Phase Margin
vs. Frequency
DS100979-A3
Gain and Phase Margin
vs. Frequency
DS100979-A2
Gain and Phase Margin
vs. Frequency
DS100979-A6
Gain and Phase Margin
vs. Frequency
DS100979-A4
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Output Voltage Swing vs.
Supply Voltage
Gain and Phase Margin
vs. Frequency
DS100979-A8
10
DS100979-A5
DS100979-A7
Unless otherwise specified, VS = +5V, single supply,
CMRR vs.
Frequency
PSRR vs.
Frequency
Input Voltage Noise vs.
Frequency
DS100979-C7
Input Current Noise vs.
Frequency
DS100979-C6
THD vs.
Frequency
THD vs.
Frequency
DS100979-F5
Slew Rate vs.
Supply Voltage
DS100979-F4
DS100979-D4
Small Signal
Non-Inverting Response
Small Signal
Non-Inverting Response
DS100979-E3
DS100979-99
11
DS100979-D3
DS100979-E2
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
Typical Performance Characteristics
TA = 25˚C. (Continued)
LMV921 Single/ LMV922 Dual/ LMV924 Quad
Typical Performance Characteristics
Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
Small Signal
Non-Inverting Response
Small Signal
Inverting Response
DS100979-E4
Small Signal
Inverting Response
DS100979-E0
Small Signal
Non-Inverting Response
DS100979-D8
Small Signal
Non-Inverting Response
DS100979-D9
Small Signal
Non-Inverting Response
DS100979-E6
Small Signal
Inverting Response
DS100979-E5
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Small Signal
Inverting Response
Small Signal
Inverting Response
DS100979-G3
12
DS100979-E7
DS100979-G2
Unless otherwise specified, VS = +5V, single supply,
Small Signal
Inverting Response
*Large Signal
Non-Inverting Response
DS100979-G1
*Large Signal
Non-Inverting Response
*Large Signal
Non-Inverting Response
DS100979-F0
*Large Signal
Inverting Response
DS100979-G0
*Large Signal
Inverting Response
DS100979-E9
*Large Signal
Inverting Response
DS100979-F9
*Large Signal
Non-Inverting Response
DS100979-F7
DS100979-F8
*Large Signal
Non-Inverting Response
DS100979-F1
DS100979-F2
*For large signal pulse response in the unity gain follower configuration, the input is 5mV below the positive rail and 5mV above
the negative rail at 25˚C and 85˚C. At −40˚C, input is 10mV below the positive rail and 10mV above the negative rail.
13
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
Typical Performance Characteristics
TA = 25˚C. (Continued)
LMV921 Single/ LMV922 Dual/ LMV924 Quad
Typical Performance Characteristics
Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
*Large Signal
Inverting Response
*Large Signal
Inverting Response
DS100979-F6
*Large Signal
Inverting Response
*Large Signal
Inverting Response
DS100979-D6
Short Circuit Current vs.
Temperature (sinking)
DS100979-E1
Short Circuit Current vs.
Temperature (sourcing)
DS100979-D7
DS100979-B5
DS100979-B6
*For large signal pulse response in the unity gain follower configuration, the input is 5mV below the positive rail and 5mV above
the negative rail at 25˚C and 85˚C. At −40˚C, input is 10mV below the positive rail and 10mV above the negative rail.
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14
LMV921 Single/ LMV922 Dual/ LMV924 Quad
Application Note
1.0 Unity Gain Pulse Response Considerations
The unity-gain follower is the most sensitive configuration to
capacitive loading. The LMV921/LMV922/LMV924 family
can directly drive 1nF in a unity-gain with minimal ringing. Direct capacitive loading reduces the phase margin of the amplifier. The combination of the amplifier’s output impedance
and the capacitive load induces phase lag. This results in either an underdamped pulse response or oscillation. The
pulse response can be improved by adding a pull up resistor
as shown in Figure 1
DS100979-41
FIGURE 1. Using a Pull-Up Resistor at the Output for
Stabilizing Capacitive Loads
Higher capacitances can be driven by decreasing the value
of the pull-up resistor, but its value shouldn’t be reduced beyond the sinking capability of the part. An alternate approach
is to use an isolation resistor as illustrated in Figure 2.
DS100979-59
FIGURE 3. Canceling the Voltage Offset Effect of Input
Bias Current
3.0 Operating Supply Voltage
The LMV921/LMV922/LMV924 family is guaranteed to operate from 1.8V to 5.0V. They will begin to function at power
voltages as low as 1.2V at room temperature when unloaded. Start up voltage increases to 1.5V when the amplifier
is fully loaded (600Ω to mid-supply). Below 1.2V the output
voltage is not guaranteed to follow the input. Figure 4 below
shows the output voltage vs. supply voltage with the
LMV921/LMV922/LMV924 configured as a voltage follower
at room temperature.
DS100979-43
FIGURE 2. Using an Isolation Resistor to Drive Heavy
Capacitive Loads
2.0 Input Bias Current Consideration
The LMV921/LMV922/LMV924 family has a bipolar input
stage. The typical input bias current (IB) is 12nA. The input
bias current can develop a significant offset voltage. This offset is primarily due to IB flowing through the negative feedback resistor, RF. For example, if IB is 50nA (max room) and
RF is 100kΩ, then an offset voltage of 5mV will develop (VOS
= IBX RF). Using a compensation resistor (RC), as shown in
Figure 3, cancels this affect. But the input offset current (IOS)
will still contribute to an offset voltage in the same manner.
DS100979-D2
FIGURE 4.
4.0 Input and Output Stage
The rail-to-rail input stage of this family provides more flexibility for the designer. The LMV921/LMV922/LMV924 use a
complimentary PNP and NPN input stage in which the PNP
stage senses common mode voltage near V− and the NPN
stage senses common mode voltage near V+. The transition
from the PNP stage to NPN stage occurs 1V below V+. Since
both input stages have their own offset voltage, the offset of
the amplifier becomes a function of the input common mode
voltage and has a crossover point at 1V below V+ as shown
in the VOS vs. VCM curves.
15
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
Application Note
high power supply rejection ratio of 78dB allows the amplifier
to be powered directly off a decaying battery voltage extending battery life.
(Continued)
This VOS crossover point can create problems for both DC
and AC coupled signals if proper care is not taken. For large
input signals that include the VOS crossover point in their dynamic range, this will cause distortion in the output signal.
One way to avoid such distortion is to keep the signal away
from the crossover. For example, in a unity gain buffer configuration and with VS = 5V, a 5V peak-to-peak signal will
contain input-crossover distortion while a 3V peak-to-peak
signal centered at 1.5V will not contain input-crossover distortion as it avoids the crossover point. Another way to avoid
large signal distortion is to use a gain of −1 circuit which
avoids any voltage excursions at the input terminals of the
amplifier. In that circuit, the common mode DC voltage can
be set at a level away from the VOS cross-over point.
For small signals, this transition in VOS shows up as a VCM
dependent spurious signal in series with the input signal and
can effectively degrade small signal parameters such as
gain and common mode rejection ratio. To resolve this problem, the small signal should be placed such that it avoids the
VOS crossover point.
In addition to the rail-to-rail performance, the output stage
can provide enough output current to drive 600Ω loads. Because of the high current capability, care should be taken not
to exceed the 150˚C maximum junction temperature specification.
5.0 Power-Supply Considerations
The LMV921/LMV922/LMV924 are ideally suited for use with
most battery-powered systems. The LMV921/LMV922/
LMV924 operate from a single +1.8V to +5.0V supply and
consumes about 145µA of supply current per Amplifier. A
Table 1 lists a variety of typical battery types. Batteries have
different voltage ratings; operating voltage is the battery voltage under nominal load. End-of-Life voltage is defined as the
voltage at which 100% of the usable power of the battery is
consumed. Table 1 also shows the typical operating time of
the LMV921.
6.0 Distortion
The two main contributors of distortion in LMV921/LMV922/
LMV924 family is:
1. Output crossover distortion occurs as the output transitions from sourcing current to sinking current.
2. Input crossover distortion occurs as the input switches
from NPN to PNP transistor at the input stage.
To decrease crossover distortion:
1. Increase the load resistance. This lowers the output crossover distortion but has no effect on the input crossover distortion.
2. Operate from a single supply with the output always
sourcing current.
3. Limit the input voltage swing for large signals between
ground and one volt below the positive supply.
4. Operate in inverting configuration to eliminate common
mode induced distortion.
5. Avoid small input signal around the input crossover region.
The discontinuity in the offset voltage will effect the gain,
CMRR and PSRR.
TABLE 1. LMV921 Characteristics with Typical Battery Systems.
Battery Type
Operating
Voltage (V)
End-of-Life
Voltage (V)
Capacity AA
Size (mA h)
LMV921
Operating
time (Hours)
Alkaline
1.5
0.9
1000
6802
Lithium
2.7
2.0
1000
6802
Ni - Cad
1.2
0.9
375
2551
NMH
1.2
1.0
500
3401
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16
1.0 Half-wave Rectifier with Rail-To-Ground Output
Swing
Since the LMV921 input common mode range includes both
positive and negative supply rails and the output can also
swing to either supply, achieving half-wave rectifier functions
in either direction is an easy task. All that is needed are two
external resistors; there is no need for diodes or matched resistors. The half wave rectifier can have either positive or
negative going outputs, depending on the way the circuit is
arranged.
DS100979-C4
DS100979-C3
DS100979-C2
FIGURE 5. Half-Wave Rectifier with Rail-To-Ground Output Swing Referenced to Ground
DS100979-C1
DS100979-C0
DS100979-B9
FIGURE 6. Half-Wave Rectifier with Negative-Going Output Referenced to VCC
17
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
In Figure 5 the circuit is referenced to ground, while in Figure
6 the circuit is biased to the positive supply. These configurations implement the half wave rectifier since the LMV921 can
not respond to one-half of the incoming waveform. It can not
respond to one-half of the incoming because the amplifier
can not swing the output beyond either rail therefore the output disengages during this half cycle. During the other half
cycle, however, the amplifier achieves a half wave that can
have a peak equal to the total supply voltage. RI should be
large enough not to load the LMV921.
Typical Applications
LMV921 Single/ LMV922 Dual/ LMV924 Quad
Typical Applications
ance is very high and require no precision matched resistors
in the input stage. They also assure that the difference amp
is driven from a voltage source. This is necessary to maintain the CMRR set by the matching R1-R2 with R3-R4.
The gain is set by the ratio of R2/R1 and R3 should equal R1
and R4 equal R2.
With both rail-to-rail input and output ranges, the input and
output are only limited by the supply voltages. Remember
that even with rail-to-rail outputs, the output can not swing
past the supplies so the combined common mode voltages
plus the signal should not be greater that the supplies or limiting will occur. For additional applications, see National
Semiconductor application notes AN–29, AN–31, AN–71,
and AN–127.
(Continued)
2.0 Instrumentation Amplifier with Rail-To-Rail Input and
Output
Using three of the LMV924 Amplifiers, an instrumentation
amplifier with rail-to-rail inputs and outputs can be made.
Some manufacturers use a precision voltage divider array of
5 resistors to divide the common mode voltage to get a
rail-to-rail input range. The problem with this method is that it
also divides the signal, so in order to get unity gain, the amplifier must be run at high loop gains. This raises the noise
and drift by the internal gain factor and lowers the input impedance. Any mismatch in these precision resistors reduces
the CMRR as well. Using the LMV924 eliminates all of these
problems.
In this example, amplifiers A and B act as buffers to the differential stage. These buffers assure that the input imped-
DS100979-G4
FIGURE 7. Rail-to-rail instrumentation amplifier
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18
LMV921 Single/ LMV922 Dual/ LMV924 Quad
SC70–5 Tape Dimensions
DS100979-96
SOT23–5 and SC70–5 Tape Format
Tape Format
Tape Section
# Cavities
Cavity Status
Cover Tape Status
Leader
0 (min)
Empty
Sealed
(Start End)
75 (min)
Empty
Sealed
Carrier
3000
Filled
Sealed
250
Filled
Sealed
Trailer
125 (min)
Empty
Sealed
(Hub End)
0 (min)
Empty
Sealed
19
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
SOT23–5 Tape Dimensions
DS100979-97
8 mm
Tape Size
www.national.com
0.130
0.124
0.130
0.126
0.138 ± 0.002
0.055 ± 0.004
0.157
0.315 ± 0.012
(3.3)
(3.15)
(3.3)
(3.2)
(3.5 ± 0.05)
(1.4 ± 0.11)
(4)
(8 ± 0.3)
DIM A
DIM Ao
DIM B
DIM Bo
DIM F
DIM Ko
DIM P1
DIM W
20
LMV921 Single/ LMV922 Dual/ LMV924 Quad
SOT23–5 and SC70–5 Reel Dimensions
DS100979-98
8 mm
Tape Size
7.00
0.059 0.512 0.795 2.165
330.00
1.50
A
B
13.00 20.20 55.00
C
D
N
21
0.331 + 0.059/−0.000
0.567
W1+ 0.078/−0.039
8.40 + 1.50/−0.00
14.40
W1 + 2.00/−1.00
W1
W2
W3
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
Physical Dimensions
inches (millimeters) unless otherwise noted
SC70-5
Order Number LMV921M7 or LMV921M7X
NS Package Number MAA05A
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22
LMV921 Single/ LMV922 Dual/ LMV924 Quad
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
SOT 23-5
Order Number LMV921M5 or LMV921M5X
NS Package Number MA05B
23
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
8-Pin MSOP
Order Number LMV922MM or LMV922MMX
NS Package Number MUA08A
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24
LMV921 Single/ LMV922 Dual/ LMV924 Quad
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
14-Pin TSSOP
Order Number LMV924MT or LMV924MTX
NS Package Number MTC14
25
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LMV921 Single/ LMV922 Dual/ LMV924 Quad
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
8-Pin SOIC
Order Number LMV922M or LMV922MX
NS Package Number M08A
www.national.com
26
inches (millimeters) unless otherwise noted (Continued)
14-Pin SOIC
Order Number LMV924M or LMV924MX
NS Package Number MA14
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LMV921 Single/ LMV922 Dual/ LMV924 Quad 1.8V, 1MHz, Low Power Operational Amplifiers with
Rail-To-Rail Input and Output
Physical Dimensions