LMV981TLX/NOPB [TI]

Single, 5-V, 1.5-MHz, 65-mA output current, RRIO operational amplifier with shutdown | YZR | 6 | -40 to 125;
LMV981TLX/NOPB
型号: LMV981TLX/NOPB
厂家: TEXAS INSTRUMENTS    TEXAS INSTRUMENTS
描述:

Single, 5-V, 1.5-MHz, 65-mA output current, RRIO operational amplifier with shutdown | YZR | 6 | -40 to 125

文件: 总20页 (文件大小:1008K)
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LMV981,LMV982  
LMV981 Single / LMV982 Dual 1.8V, RRIO Operational Amplifiers with Shutdown  
Literature Number: SNOS976K  
October 13, 2010  
LMV981 Single / LMV982 Dual  
1.8V, RRIO Operational Amplifiers with Shutdown  
General Description  
Features  
LMV981/LMV982 are low voltage, low power operational am-  
plifiers. LMV981/LMV982 operate from +1.8V to +5.0V supply  
voltages and have rail-to-rail input and output. LMV981/  
LMV982 input common mode voltage extends 200mV be-  
yond the supplies which enables user enhanced functionality  
beyond the supply voltage range. The output can swing rail-  
to-rail unloaded and within 105mV from the rail with 600load  
at 1.8V supply. LMV981/LMV982 are optimized to work at  
1.8V which make them ideal for portable two-cell battery pow-  
ered systems and single cell Li-Ion systems.  
(Typical 1.8V Supply Values; Unless Otherwise Noted)  
Guaranteed 1.8V, 2.7V and 5V specifications  
Output swing  
w/600load  
w/2kload  
VCM  
80mV from rail  
30mV from rail  
200mV beyond rails  
Supply current (per channel)  
Gain bandwidth product  
Maximum VOS  
100μA  
1.4MHz  
4.0mV  
Gain w/600load  
101dB  
1.0mm x 1.5mm  
LMV981/LMV982 offer a shutdown pin that can be used to  
disable the device and reduce the supply current. The device  
is in shutdown when the SHDN-pin = low. The output will be  
high impedance in shutdown.  
Ultra tiny package micro SMD  
Turn-on time from shutdown  
Temperature range  
19μs  
−40°C to 125°C  
LMV981/LMV982 exhibit excellent speed-power ratio,  
achieving 1.4MHz gain bandwidth product at 1.8V supply  
voltage with very low supply current. LMV981/LMV982 are  
capable of driving a 600load and up to 1000pF capacitive  
load with minimal ringing. LMV981/LMV982 have a high DC  
gain of 101dB, making them suitable for low frequency appli-  
cations.  
Applications  
Industrial and automotive  
Consumer communication  
Consumer computing  
PDAs  
LMV981 is offered in space saving 6-Bump micro SMD,  
SC70-6 and SOT23-6 packages. The 6-Bump micro SMD  
package has only a 1.006mm x 1.514mm x 0.945mm foot-  
print. LMV982 is offered in space saving MSOP-10 package.  
These small packages are ideal solutions for area con-  
strained PC boards and portable electronics such as cellular  
phones and PDAs.  
Portable audio  
Portable/battery-powered electronic equipment  
Supply current monitoring  
Battery monitoring  
Typical Application  
200214h0  
© 2010 National Semiconductor Corporation  
200214  
www.national.com  
For soldering specifications:  
see product folder at www.national.com and  
www.national.com/ms/MS/MS-SOLDERING.pdf  
Absolute Maximum Ratings (Note 1)  
If Military/Aerospace specified devices are required,  
please contact the National Semiconductor Sales Office/  
Distributors for availability and specifications.  
Operating Ratings (Note 1)  
ESD Tolerance (Note 2)  
Supply Voltage Range  
Temperature Range  
Thermal Resistance (θJA  
6-Bump micro SMD  
SC70-6  
1.8V to 5.0V  
−40°C to 125°C  
Machine Model  
Human Body Model  
200V  
2000V  
)
Supply Voltage (V+–V )  
Differential Input Voltage  
Voltage at Input/Output Pins  
Storage Temperature Range  
Junction Temperature (Note 4)  
5.5V  
286°C/W  
414°C/W  
265°C/W  
235°C/W  
± Supply Voltage  
V++0.3V, V- -0.3V  
−65°C to 150°C  
150°C  
SOT23-6  
MSOP-10  
1.8V DC Electrical Characteristics  
Unless otherwise specified, all limits guaranteed for TJ = 25°C. V+ = 1.8V, V = 0V, VCM = V+/2, VO = V+/2,  
RL > 1 Mand SHDN tied to V+. Boldface limits apply at the temperature extremes. See (Note 10).  
Symbol  
Parameter  
Condition  
LMV981 (Single)  
LMV982 (Dual)  
Min  
(Note 6)  
Typ  
(Note 5)  
Max  
(Note 6)  
Units  
VOS  
Input Offset Voltage  
1
1
4
6
mV  
5.5  
7.5  
TCVOS  
IB  
Input Offset Voltage Average  
Drift  
5.5  
15  
μV/°C  
nA  
Input Bias Current  
35  
50  
IOS  
Input Offset Current  
13  
25  
40  
nA  
IS  
Supply Current (per channel)  
103  
0.156  
0.178  
78  
185  
205  
In Shutdown  
LMV981 (Single)  
LMV982 (Dual)  
1
2
μA  
3.5  
5
CMRR  
Common Mode Rejection Ratio  
60  
55  
LMV981, 0 VCM 0.6V  
1.4V VCM 1.8V  
(Note 8)  
55  
50  
76  
72  
LMV982, 0 VCM 0.6V  
1.4V VCM 1.8V (Note 8)  
dB  
50  
−0.2V VCM 0V  
1.8V VCM 2.0V  
1.8V V+ 5V  
PSRR  
CMVR  
Power Supply Rejection Ratio  
75  
70  
V−0.2  
V−  
100  
dB  
V
Input Common-Mode Voltage For CMRR  
Range  
TA = 25°C  
−0.2 to 2.1  
V+ +0.2  
V+  
Range 50dB  
TA = −40°C to 85°C  
TA = 125°C  
V+0.2  
V+ −0.2  
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2
Symbol  
Parameter  
Condition  
RL = 600Ω to 0.9V,  
Min  
(Note 6)  
Typ  
(Note 5)  
Max  
(Note 6)  
Units  
AV  
Large Signal Voltage Gain  
LMV981 (Single)  
77  
73  
101  
105  
90  
VO = 0.2V to 1.6V, VCM = 0.5V  
dB  
80  
75  
RL = 2kto 0.9V,  
VO = 0.2V to 1.6V, VCM = 0.5V  
Large Signal Voltage Gain  
LMV982 (Dual)  
75  
72  
RL = 600Ω to 0.9V,  
VO = 0.2V to 1.6V, VCM = 0.5V  
dB  
78  
75  
100  
RL = 2kto 0.9V,  
VO = 0.2V to 1.6V, VCM = 0.5V  
VO  
Output Swing  
1.65  
1.63  
1.72  
0.077  
1.77  
0.024  
8
RL = 600Ω to 0.9V  
VIN = ± 100mV  
0.105  
0.120  
V
1.75  
1.74  
RL = 2kto 0.9V  
VIN = ± 100mV  
0.035  
0.04  
IO  
Output Short Circuit Current  
(Note 3)  
Sourcing, VO = 0V  
VIN = 100mV  
4
3.3  
mA  
Sinking, VO = 1.8V  
VIN = −100mV  
7
5
9
Ton  
Turn-on Time from Shutdown  
Turn-on Voltage to enable part  
Turn-off Voltage  
19  
1.0  
μs  
VSHDN  
V
0.55  
1.8V AC Electrical Characteristics  
Unless otherwise specified, all limits guaranteed for TJ = 25°C. V+ = 1.8V, V = 0V, VCM = V+/2, VO = V+/2,  
RL > 1 Mand SHDN tied to V+. Boldface limits apply at the temperature extremes. See (Note 10).  
Symbol  
Parameter  
Conditions  
Min  
Typ  
Max  
Units  
(Note 6)  
(Note 5)  
(Note 6)  
SR  
Slew Rate  
(Note 7)  
0.35  
1.4  
67  
V/μs  
MHz  
deg  
dB  
GBW  
Φm  
Gm  
Gain-Bandwidth Product  
Phase Margin  
Gain Margin  
7
en  
Input-Referred Voltage Noise  
f = 10 kHz, VCM = 0.5V  
f = 10 kHz  
60  
in  
Input-Referred Current Noise  
Total Harmonic Distortion  
0.08  
THD  
f = 1kHz, AV = +1  
RL = 600Ω, VIN = 1 VPP  
(Note 9)  
0.023  
%
Amp-to-Amp Isolation  
123  
dB  
2.7V DC Electrical Characteristics  
Unless otherwise specified, all limits guaranteed for TJ = 25°C. V+ = 2.7V, V = 0V, VCM = V+/2, VO = V+/2,  
RL > 1 Mand SHDN tied to V+. Boldface limits apply at the temperature extremes. See (Note 10).  
Symbol  
Parameter  
Condition  
LMV981 (Single)  
LMV982 (Dual)  
Min  
(Note 6)  
Typ  
(Note 5)  
Max  
(Note 6)  
Units  
VOS  
Input Offset Voltage  
1
1
4
6
mV  
mV  
6
7.5  
3
www.national.com  
Symbol  
TCVOS  
IB  
Parameter  
Condition  
Min  
(Note 6)  
Typ  
(Note 5)  
Max  
(Note 6)  
Units  
Input Offset Voltage Average  
Drift  
5.5  
15  
μV/°C  
nA  
Input Bias Current  
35  
50  
IOS  
Input Offset Current  
8
25  
40  
nA  
IS  
Supply Current (per channel)  
105  
0.061  
0.101  
81  
190  
210  
In Shutdown  
LMV981 (Single)  
LMV982 (Dual)  
1
2
μA  
3.5  
5
CMRR  
Common Mode Rejection Ratio  
60  
55  
LMV981, 0 VCM 1.5V  
2.3V VCM 2.7V (Note 8)  
55  
50  
80  
74  
LMV982, 0 VCM 1.5V  
2.3V VCM 2.7V (Note 8)  
dB  
50  
−0.2V VCM 0V  
2.7V VCM 2.9V  
1.8V V+ 5V  
PSRR  
CMVR  
Power Supply Rejection Ratio  
75  
70  
100  
dB  
V
VCM = 0.5V  
Input Common-Mode Voltage For CMRR  
Range  
TA = 25°C  
V−0.2  
V−  
−0.2 to 3.0  
V ++0.2  
V+  
Range 50dB  
TA = −40°C to 85°C  
TA = 125°C  
V+0.2  
V +−0.2  
AV  
Large Signal Voltage Gain  
LMV981(Single)  
87  
86  
104  
110  
90  
RL = 600Ω to 1.35V,  
VO = 0.2V to 2.5V  
92  
91  
RL = 2kto 1.35V,  
VO = 0.2V to 2.5V  
dB  
Large Signal Voltage Gain  
LMV982 (Dual)  
78  
75  
RL = 600Ω to 1.35V,  
VO = 0.2V to 2.5V  
81  
78  
100  
RL = 2kto 1.35V,  
VO = 0.2V to 2.5V  
VO  
Output Swing  
2.55  
2.53  
2.62  
0.083  
2.675  
0.025  
30  
RL = 600Ω to 1.35V  
VIN = ±100mV  
0.110  
0.130  
V
2.65  
2.64  
RL = 2kto 1.35V  
VIN = ±100mV  
0.04  
0.045  
IO  
Output Short Circuit Current  
(Note 3)  
Sourcing, VO = 0V  
VIN = 100mV  
20  
15  
mA  
Sinking, VO = 0V  
VIN = −100mV  
18  
12  
25  
Ton  
Turn-on Time from Shutdown  
Turn-on Voltage to enable part  
Turn-off Voltage  
12.5  
1.9  
μs  
VSHDN  
V
0.8  
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4
2.7V AC Electrical Characteristics  
Unless otherwise specified, all limits guaranteed for TJ = 25°C. V+ = 2.7V, V = 0V, VCM = 1.0V, VO = 1.35V,  
RL > 1 Mand SHDN tied to V+. Boldface limits apply at the temperature extremes. See (Note 10).  
Symbol  
Parameter  
Conditions  
Min  
Typ  
Max  
Units  
(Note 6)  
(Note 5)  
(Note 6)  
SR  
GBW  
Φm  
Gm  
en  
Slew Rate  
(Note 7)  
0.4  
1.4  
70  
V/µs  
MHz  
deg  
dB  
Gain-Bandwidth Product  
Phase Margin  
Gain Margin  
7.5  
57  
Input-Referred Voltage Noise f = 10 kHz, VCM = 0.5V  
in  
Input-Referred Current Noise f = 10 kHz  
0.08  
THD  
Total Harmonic Distortion  
Amp-to-Amp Isolation  
f = 1kHz, AV = +1  
RL = 600Ω, VIN = 1VPP  
(Note 9)  
0.022  
123  
%
dB  
5V DC Electrical Characteristics  
Unless otherwise specified, all limits guaranteed for TJ = 25°C. V+ = 5V, V = 0V, VCM = V+/2, VO = V+/2,  
RL > 1 Mand SHDN tied to V+. Boldface limits apply at the temperature extremes. See (Note 10).  
Symbol  
Parameter  
Condition  
Min  
Typ  
Max  
Units  
(Note 6)  
(Note 5)  
(Note 6)  
VOS  
Input Offset Voltage  
LMV981 (Single)  
1
1
4
6
mV  
LMV982 (Dual)  
5.5  
7.5  
TCVOS  
IB  
Input Offset Voltage Average  
Drift  
5.5  
14  
μV/°C  
nA  
Input Bias Current  
35  
50  
IOS  
Input Offset Current  
9
25  
40  
nA  
IS  
Supply Current (per Channel)  
116  
0.201  
0.302  
86  
210  
230  
μA  
In Shutdown  
LMV981 (Single)  
LMV982 (Dual)  
1
2
μA  
3.5  
5
CMRR  
Common Mode Rejection Ratio  
Power Supply Rejection Ratio  
60  
55  
0 VCM 3.8V  
4.6V VCM 5.0V (Note 8)  
dB  
50  
78  
−0.2V VCM 0V  
5.0V VCM 5.2V  
1.8V V+ 5V  
VCM = 0.5V  
PSRR  
CMVR  
75  
70  
100  
dB  
V
Input Common-Mode Voltage For CMRR  
Range  
TA = 25°C  
V−0.2  
V−  
−0.2 to 5.3  
V+ +0.2  
V+  
Range 50dB  
TA = −40°C to 85°C  
TA = 125°C  
V+0.3  
V+ −0.3  
5
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Symbol  
Parameter  
Condition  
RL = 600Ω to 2.5V,  
Min  
(Note 6)  
Typ  
(Note 5)  
Max  
(Note 6)  
Units  
AV  
Large Signal Voltage Gain  
(LMV981 Single)  
88  
87  
102  
113  
90  
VO = 0.2V to 4.8V  
dB  
94  
93  
RL = 2kto 2.5V,  
VO = 0.2V to 4.8V  
Large Signal Voltage Gain  
LMV982 (Dual)  
81  
78  
RL = 600Ω to 2.5V,  
VO = 0.2V to 4.8V  
dB  
85  
82  
100  
RL = 2kto 2.5V,  
VO = 0.2V to 4.8V  
VO  
Output Swing  
4.855  
4.835  
4.890  
0.120  
4.967  
0.037  
100  
RL = 600Ω to 2.5V  
VIN = ±100mV (Note 8)  
0.160  
0.180  
V
4.945  
4.935  
RL = 2kto 2.5V  
VIN = ±100mV  
0.065  
0.075  
IO  
Output Short Circuit Current  
(Note 3)  
LMV981, Sourcing, VO = 0V  
VIN = 100mV  
80  
68  
mA  
Sinking, VO = 5V  
VIN = −100mV  
58  
45  
65  
Ton  
Turn-on Time from Shutdown  
Turn-on Voltage to enable part  
Turn-off Voltage  
8.4  
4.2  
0.8  
μs  
VSHDN  
V
5V AC Electrical Characteristics  
Unless otherwise specified, all limits guaranteed for TJ = 25°C. V+ = 5V, V = 0V, VCM = V+/2, VO = 2.5V,  
R L > 1 Mand SHDN tied to V+.Boldface limits apply at the temperature extremes. See (Note 10).  
Symbol  
Parameter  
Conditions  
Min  
Typ  
Max  
Units  
(Note 6)  
(Note 5)  
(Note 6)  
SR  
Slew Rate  
(Note 7)  
0.42  
1.5  
71  
V/µs  
MHz  
deg  
GBW  
Φm  
Gm  
Gain-Bandwidth Product  
Phase Margin  
Gain Margin  
8
dB  
en  
Input-Referred Voltage Noise f = 10 kHz, VCM = 1V  
50  
in  
Input-Referred Current Noise  
Total Harmonic Distortion  
f = 10 kHz  
0.08  
THD  
f = 1kHz, AV = +1  
RL = 600Ω, VO = 1V PP  
(Note 9)  
0.022  
%
Amp-to-Amp Isolation  
123  
dB  
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6
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, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC)  
Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC).  
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 45mA 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 as determined at the time of characterization. Actual typical values may vary over time and will  
also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material.  
Note 6: All limits are guaranteed by testing or statistical analysis.  
Note 7: Connected as voltage follower with input step from Vto V+. Number specified is the slower of the positive and negative slew rates.  
Note 8: For guaranteed temperature ranges, see Input Common-Mode Voltage Range specifications.  
Note 9: Input referred, RL = 100kconnected to V+/2. Each amp excited in turn with 1kHz to produce VO = 3VPP. (For Supply Voltages <3V, VO = V+).  
Note 10: Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating  
of the device such that TJ = TA. No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self heating where TJ >  
TA. See Applications section for information on temperature derating of this device. Absolute Maximum Ratings indicated junction temperature limits beyond which  
the device may be permanently degraded, either mechanically or electrically.  
Connection Diagrams  
6-Bump micro SMD  
6-Pin SC70-6/SOT23-6  
10-Pin MSOP  
200214g7  
Top View  
20021435  
200214g6  
Top View  
Top View  
Ordering Information  
Package  
Part Number  
Packaging Marking  
Transport Media  
NSC Drawing  
6-Bump micro SMD  
(NOPB)  
LMV981TL  
LMV981TLX  
LMV981MG  
LMV981MGX  
LMV981MF  
LMV981MFX  
LMV982MM  
LMV982MMX  
H
250 Units Tape and Reel  
3k Units Tape and Reel  
1k Units Tape and Reel  
3k Units Tape and Reel  
1k Units Tape and Reel  
3.5k Units Tape and Reel  
1k Units Tape and Reel  
3.5k Units Tape and Reel  
TLA06BBA  
6-Pin SC70  
6-Pin SOT23  
10-Pin MSOP  
A77  
MA006A  
MF06A  
A78A  
A87A  
MUB10A  
7
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Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply, TA = 25°C.  
Supply Current vs. Supply Voltage (LMV981)  
Sourcing Current vs. Output Voltage  
20021425  
20021422  
Sinking Current vs. Output Voltage  
Output Voltage Swing vs. Supply Voltage  
20021428  
20021449  
Output Voltage Swing vs. Supply Voltage  
Gain and Phase vs. Frequency  
20021450  
200214g8  
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8
Gain and Phase vs. Frequency  
Gain and Phase vs. Frequency  
PSRR vs. Frequency  
Gain and Phase vs. Frequency  
200214g9  
200214g10  
CMRR vs. Frequency  
20021439  
200214g11  
Input Voltage Noise vs. Frequency  
20021456  
20021458  
9
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Input Current Noise vs. Frequency  
THD vs. Frequency  
20021466  
20021467  
THD vs. Frequency  
Slew Rate vs. Supply Voltage  
20021469  
20021468  
Small Signal Non-Inverting Response  
Small Signal Non-Inverting Response  
20021470  
20021471  
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10  
Small Signal Non-Inverting Response  
Large Signal Non-Inverting Response  
20021473  
20021472  
Large Signal Non-Inverting Response  
Large Signal Non-Inverting Response  
20021474  
20021475  
Short Circuit Current vs. Temperature (Sinking)  
Short Circuit Current vs. Temperature (Sourcing)  
20021476  
20021477  
11  
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Offset Voltage vs. Common Mode Range  
Offset Voltage vs. Common Mode Range  
20021436  
20021437  
Offset Voltage vs. Common Mode Range  
20021438  
pendent 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  
600loads. Because of the high current capability, care  
should be taken not to exceed the 150°C maximum junction  
temperature specification.  
Application Note  
INPUT AND OUTPUT STAGE  
The rail-to-rail input stage of this family provides more flexi-  
bility for the designer. The LMV981/LMV982 use a compli-  
mentary PNP and NPN input stage in which the PNP stage  
senses common mode voltage near Vand 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 volt-  
age and has a crossover point at 1V below V+.  
SHUTDOWN MODE  
The LMV981/LMV982 have a shutdown pin. To conserve bat-  
tery life in portable applications, the LMV981/LMV982 can be  
disabled when the shutdown pin voltage is pulled low.  
This VOS crossover point can create problems for both DC and  
AC coupled signals if proper care is not taken. Large input  
signals that include the VOS crossover point will cause distor-  
tion 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 de-  
The shutdown pin can’t be left unconnected. In case shut-  
down operation is not needed, the shutdown pin should be  
connected to V+ when the LMV981/LMV982 are used. Leav-  
ing the shutdown pin floating will result in an undefined oper-  
ation mode, either shutdown or active, or even oscillating  
between the two modes.  
INPUT BIAS CURRENT CONSIDERATION  
The LMV981/LMV982 family has a complementary bipolar  
input stage. The typical input bias current (IB) is 15nA. The  
input bias current can develop a significant offset voltage.  
This offset is primarily due to IB flowing through the negative  
www.national.com  
12  
feedback resistor, RF. For example, if IB is 50nA and RF is  
100k, then an offset voltage of 5mV will develop (VOS = IB x  
RF). Using a compensation resistor (RC), as shown in Figure  
1, cancels this effect. But the input offset current (IOS) will still  
contribute to an offset voltage in the same manner.  
tion because the common mode input range goes up to the  
rail.  
200214h0  
FIGURE 2. High Side Current Sensing  
HALF-WAVE RECTIFIER WITH RAIL-TO-GROUND  
OUTPUT SWING  
Since the LMV981/LMV982 input common mode range in-  
cludes 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.  
20021459  
FIGURE 1. Canceling the Offset Voltage due to Input Bias  
Current  
In Figure 3 the circuit is referenced to ground, while in Figure  
4 the circuit is biased to the positive supply. These configu-  
rations implement the half wave rectifier since the LMV981/  
LMV982 can not respond to one-half of the incoming wave-  
form. It can not respond to one-half of the incoming because  
the amplifier can not swing the output beyond either rail there-  
fore 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 LMV981/LMV982.  
Typical Applications  
HIGH SIDE CURRENT SENSING  
The high side current sensing circuit (Figure 2) is commonly  
used in a battery charger to monitor charging current to pre-  
vent over charging. A sense resistor RSENSE is connected to  
the battery directly. This system requires an op amp with rail-  
to-rail input. The LMV981/LMV982 are ideal for this applica-  
200214c4  
200214c2  
200214c3  
FIGURE 3. Half-Wave Rectifier with Rail-To-Ground Output Swing Referenced to Ground  
13  
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200214c1  
200214b9  
200214c0  
FIGURE 4. Half-Wave Rectifier with Negative-Going Output Referenced to VCC  
INSTRUMENTATION AMPLIFIER WITH RAIL-TO-RAIL  
INPUT AND OUTPUT  
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 sup-  
plies or limiting will occur. For additional applications, see  
National Semiconductor application notes AN–29, AN–31,  
AN–71, and AN–127.  
Some manufactures make a non-“rail-to-rail”-op amp rail-to-  
rail by using a resistive divider on the inputs. The resistors  
divide the input 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 the obtained gain, the amplifier must have a  
higher closed loop gain. This raises the noise and drift by the  
internal gain factor and lowers the input impedance. Any mis-  
match in these precision resistors reduces the CMRR as well.  
The LMV981/LMV982 is rail-to-rail and therefore doesn’t  
have these disadvantages.  
Using three of the LMV981/LMV982 amplifiers, an instrumen-  
tation amplifier with rail-to-rail inputs and outputs can be made  
as shown in Figure 5.  
In this example, amplifiers on the left side act as buffers to the  
differential stage. These buffers assure that the input  
impedance is very high and require no precision matched re-  
sistors 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,  
200214g4  
FIGURE 5. Rail-to-rail instrumentation amplifier  
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14  
 
 
Simplified Schematic  
200214a9  
15  
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Physical Dimensions inches (millimeters) unless otherwise noted  
NOTES: UNLESS OTHERWISE SPECIFIED  
1. EPOXY COATING  
2. FOR SOLDER BUMP COMPOSITION, SEE “SOLDER INFORMATION” IN THE PACKAGING SECTION OF THE NATATION SEMICONDUCTOR WEB PAGE  
(www.national.com)  
3. RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD.  
4. PIN A1 IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEXT ORIENTATION.  
5. XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1 IS PACKAGE WIDTH, X2 IS PACKAGE LENGTH AND X3 IS PACK-  
AGE HEIGHT.  
6. REFERENCE JEDEC REGISTRATION MO-211, VARIATION DB.  
6-Bump micro SMD  
NS Package Number TLA06BBA  
X1 = 1.031 ±0.030mm X2 = 1.539 ±0.030mm X3 = 0.600 ±0.075mm  
6-Pin SC70  
NS Package Number MAA06A  
www.national.com  
16  
6-Pin SOT23  
NS Package Number MF06A  
10-Pin MSOP  
NS Package Number MUB10A  
17  
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Notes  
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