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LMV921/LMV922/LMV924 Single, Dual and Quad 1.8V, 1MHz, Low Power Operational Amplifiers with Rail-To-Rail Input and Output
December 2001
LMV921/LMV922/LMV924 Single, Dual and Quad 1.8V, 1MHz, Low Power Operational Amplifiers with Rail-To-Rail Input and Output
General Description
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 600 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 600 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.
Features
(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/600 load 100 mV from rail -- w/2k load 30 mV from rail n VCM 300mV beyond rails n Supply current 145A/amplifier n Gain bandwidth product 1MHz n LMV921 Maximum VOS 6mV n 90dB gain w/600 load 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
Supply Current vs. Supply Voltage (LMV921)
Output Voltage Swing vs. Supply Voltage
Gain and Phase Margin vs. Frequency
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(c) 2001 National Semiconductor Corporation
DS100979
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LMV921/LMV922/LMV924
Absolute Maximum Ratings
(Note 1)
Operating Ratings (Note 1)
Supply Voltage Temperature Range Thermal Resistance (JA) Ultra Tiny SC70-5 Package 5-Pin Surface Mount Tiny SOT23-5 Package 5-Pin Surface Mount MSOP Package 8-Pin Surface Mount TSSOP Package 14-Pin Surface Mount SOIC Package 8-Pin Surface Mount 14-Pin Surface Mount 1.5V to 5.0V -40C TJ 85C
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 2) Machine Model Human Body Model Differential Input Voltage Supply Voltage (V+-V -) Output Short Circuit to V+ (Note 3) Output Short Circuit to V- (Note 3) Storage Temperature Range Junction Temperature (Note 4) Mounting Temp. Infrared or Convection (20 sec) 235C -65C to 150C 150C 100V 2000V
440 C/W 265 C/W 235C/W 155C/W 175C/W 127C/W
Supply Voltage
5.5V
1.8V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 1.8V, V RL > 1 M. Boldface limits apply at the temperature extremes. Symbol VOS Parameter Input Offset Voltage Condition LMV921 (Single) LMV922 (Dual) LMV924 (Quad) TCVOS IB IOS IS Input Offset Voltage Average Drift Input Bias Current Input Offset Current Supply Current LMV921 (Single) LMV922 (Dual) LMV924 (Quad) CMRR Common Mode Rejection Ratio 0 VCM 0.6V -0.2V VCM 0V 1.8V VCM 2.0V PSRR VCM Power Supply Rejection Ratio Input Common-Mode Voltage Range 1.8V V+ 5V, VCM = 0.5V For CMRR 50dB
-
= 0V, VCM = V+/2, VO = V+/2 and Typ (Note 5) -1.8 -1.8 1 12 2 145 330 560 82 74 78 -0.3 2.15 35 50 25 40 185 205 400 550 700 850 62 60 50 67 62 -0.2 0 2.0 1.8 dB min dB min V min V max A max Limits (Note 6) 6 8 8 9.5 Units mV max mV max V/C nA max nA max
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LMV921/LMV922/LMV924
1.8V DC Electrical Characteristics
Symbol AV Parameter Large Signal Voltage Gain LMV921 (Single)
(Continued) Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 1.8V, V RL > 1 M. Boldface limits apply at the temperature extremes. Condition RL = 600 to 0.9V, VO = 0.2V to 1.6V, VCM = 0.5V RL = 2k to 0.9V, VO = 0.2V to 1.6V, VCM = 0.5V Large Signal Voltage Gain LMV922 (Dual) LMV924 (Quad) RL = 600 to 0.9V, VO = 0.2V to 1.6V, VCM = 0.5V RL = 2k to 0.9V, VO = 0.2V to 1.6V, VCM = 0.5V RL = 600 to 0.9V VIN = 100mV
-
= 0V, VCM = V+/2, VO = V+/2 and Typ (Note 5) 91 95 79 83 1.7 0.075 Limits (Note 6) 77 73 80 75 65 61 68 63 1.65 1.63 0.090 0.105 1.75 1.74 0.035 0.040 4 3.3 7 5 Units
dB min
dB min V min V max V min V max mA min mA min
VO
Output Swing
RL = 2k to 0.9V VIN = 100mV
1.77 0.025
IO
Output Short Circuit Current
Sourcing, VO = 0V VIN = 100mV Sinking, VO = 1.8V VIN = -100mV
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1.8V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 1.8V, V Boldface limits apply at the temperature extremes. Symbol SR GBW m Gm en in THD Parameter Slew Rate Gain-Bandwidth Product Phase Margin Gain Margin Input-Referred Voltage Noise Input-Referred Current Noise Total Harmonic Distortion Amp-to-Amp Isolation f = 1 kHz, VCM = 0.5V f = 1 kHz f = 1kHz, AV = +1 RL = 600k, VIN = 1 VPP (Note 8) (Note 7) Conditions
-
= 0V, VCM = V+/2, VO = V+/2 and RL > 1 M. Typ (Note 5) 0.39 1 60 10 45 0.1 Units V/s MHz Deg dB
0.089 140
% dB
2.7V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 2.7V, V RL > 1 M. Boldface limits apply at the temperature extremes. Symbol VOS Parameter Input Offset Voltage Condition LMV921 (Single) LMV922 (Dual) LMV924 (Quad)
-
= 0V, VCM = V+/2, VO = V+/2 and Typ (Note 5) -1.6 -1.6 Limits (Note 6) 6 8 8 9.5 Units mV max mV max
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LMV921/LMV922/LMV924
2.7V DC Electrical Characteristics
Symbol TCVOS IB IOS IS Parameter Input Offset Voltage Average Drift Input Bias Current Input Offset Current Supply Current
(Continued) Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 2.7V, V RL > 1 M. Boldface limits apply at the temperature extremes. Condition
-
= 0V, VCM = V+/2, VO = V+/2 and Typ (Note 5) 1 12 2 35 50 25 40 190 210 450 600 750 900 62 60 50 67 62 -0.2 0 2.9 2.7 80 75 83 77 68 63 71 65 2.550 2.530 0.095 0.115 2.650 2.640 0.040 0.045 20 15 22 16 dB min dB min V min V max dB min uA max Limits (Note 6) Units V/C nA max nA max
LMV921 (Single) LMV922 (Dual) LMV924 (Quad)
147 380 580 84 73 78 -0.3 3.050
CMRR
Common Mode Rejection Ratio
0V VCM 1.5V -0.2V VCM 0V 2.7V VCM < 2.9V
PSRR VCM
Power Supply Rejection Ratio Input Common-Mode Voltage Range
1.8V V+ 5V, VCM = 0.5V For CMRR 50dB
AV
Large Signal Voltage Gain LMV921 (Single)
RL = 600 to 1.35V, VO = 0.2V to 2.5V RL = 2k to 1.35V, VO = 0.2V to 2.5V
98 103 86 91 2.62 0.075
Large Signal Voltage Gain LMV922 (Dual) LMV924 (Quad) VO Output Swing
RL = 600 to 1.35V, VO = 0.2V to 2.5V RL = 2k to 1.35V, VO = 0.2V to 2.5V RL = 600 to 1.35V VIN = 100mV
dB min V min V max V min V max mA min mA min
RL = 2k to 1.35V VIN = 100mV
2.675 0.025
IO
Output Short Circuit Current
Sourcing, VO = 0V VIN = 100mV Sinking, VO = 2.7V VIN = -100mV
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2.7V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 2.7V, V RL > 1 M. Boldface limits apply at the temperature extremes. Symbol SR Slew Rate Parameter (Note 7)
-
= 0V, VCM = 1.0V, VO = 1.35V and Typ (Note 5) 0.41 Units V/s
Conditions
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LMV921/LMV922/LMV924
2.7V AC Electrical Characteristics
Symbol GBW m Gm en in THD Parameter Gain-Bandwidth Product Phase Margin Gain Margin Input-Referred Voltage Noise Input-Referred Current Noise Total Harmonic Distortion Amp-to-Amp Isolation
(Continued) Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 2.7V, V RL > 1 M. Boldface limits apply at the temperature extremes.
-
= 0V, VCM = 1.0V, VO = 1.35V and Typ (Note 5) 1 65 10 Units MHz Deg. dB
Conditions
f = 1 kHz, VCM = 0.5V f = 1 kHz f = 1 kHz, AV = +1 RL = 600k, VIN = 1 VPP (Note 8)
45 0.1
0.077 140
% dB
5V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 5V, V RL > 1 M.Boldface limits apply at the temperature extremes. Symbol VOS Parameter Input Offset Voltage Condition LMV921 (Single) LMV922 (Dual) LMV924 (Quad) TCVOS IB IOS IS Input Offset Voltage Average Drift Input Bias Current Input Offset Current Supply Current LMV921 (Single) LMV922 (Dual) LMV924 (Quad) CMRR Common Mode Rejection Ratio 0V VCM 3.8V -0.2V VCM 0V 5.0V VCM 5.2V PSRR VCM Power Supply Rejection Ratio Input Common-Mode Voltage Range 1.8V V+ 5V VCM = 0.5V For CMRR 50dB
-
= 0V, VCM = V+/2, VO = V+/2 and Typ (Note 5) -1.5 -1.5 1 12 2 160 400 750 86 72 78 -0.3 5.350 35 50 25 40 210 230 500 700 850 980 62 61 50 67 62 -0.2 0 5.2 5.0 dB min dB min V min V max A max Limits (Note 6) 6 8 8 9.5 Units mV max mV max V/C nA max nA max
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LMV921/LMV922/LMV924
5V DC Electrical Characteristics
Symbol AV Parameter Voltage Gain LMV921 (Single)
(Continued) Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 5V, V RL > 1 M.Boldface limits apply at the temperature extremes. Condition RL = 600 to 2.5V VO = 0.2V to 4.8V RL = 2k to 2.5V VO = 0.2V to 4.8V Voltage Gain LMV922 (Dual) LMV924 (Quad) RL = 600 to 2.5V VO = 0.2V to 4.8V RL = 2k to 2.5V VO = 0.2V to 4.8V RL = 600 to 2.5V VIN = 100mV
-
= 0V, VCM = V+/2, VO = V+/2 and Typ (Note 5) 104 108 90 96 4.895 0.1 Limits (Note 6) 86 82 89 85 72 68 77 73 4.865 4.840 0.135 0.160 4.945 4.935 0.065 0.075 85 68 35 65 45 Units
dB min
dB min V min V max V min V max mA min mA min
VO
Output Swing
RL = 2k to 2.5V VIN = 100mV
4.965 0.035
IO
Output Short Circuit Current
LMV921 Sourcing, VO = 0V VIN = 100mV LMV922, LMV924 Sourcing, VO = 0V VIN = 100mV Sinking, VO = 5V VIN = -100mV
98 60 75
5V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25C. V+ = 5V, V R L > 1 M. Boldface limits apply at the temperature extremes. Symbol SR GBW m Gm en in THD Slew Rate Gain-Bandwidth Product Phase Margin Gain Margin Input-Referred Voltage Noise Input-Referred Current Noise Total Harmonic Distortion Amp-to-Amp Isolation f = 1 kHz, VCM = 1V f = 1 kHz f = 1 kHz, AV = +1 RL = 600, VO = 1 V (Note 8) Parameter (Note 7)
-
= 0V, VCM = V+/2, VO = 2.5V and Typ (Note 5) 0.45 1 70 15 45 0.1 0.069
PP
Conditions
Units V/s MHz Deg dB
% dB
140
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 k in series with 100pF. Machine model, 200 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 150C. 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) , JA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max)-T A)/JA. 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 = 100k connected to 2.5V. Each amp excited in turn with 1kHz to produce VO = 3VPP.
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LMV921/LMV922/LMV924
Typical Performance Characteristics
TA = 25C. Supply Current vs. Supply Voltage (LMV921)
Unless otherwise specified, VS = +5V, single supply, Input Bias Current vs. VCM
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Sourcing Current vs. Output Voltage
Sourcing Current vs. Output Voltage
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Sourcing Current vs. Output Voltage
Sinking Current vs. Output Voltage
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LMV921/LMV922/LMV924
Typical Performance Characteristics
TA = 25C. (Continued) Sinking Current vs. Output Voltage
Unless otherwise specified, VS = +5V, single supply,
Sinking Current vs. Output Voltage
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Offset Voltage vs. Common Mode Voltage
Offset Voltage vs. Common Mode Voltage
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Offset Voltage vs. Common Mode Voltage
Output Voltage Swing vs. Supply Voltage
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LMV921/LMV922/LMV924
Typical Performance Characteristics
TA = 25C. (Continued) Output Voltage Swing vs. Supply Voltage
Unless otherwise specified, VS = +5V, single supply,
Gain and Phase Margin vs. Frequency
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Gain and Phase Margin vs. Frequency
Gain and Phase Margin vs. Frequency
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Gain and Phase Margin vs. Frequency
Gain and Phase Margin vs. Frequency
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LMV921/LMV922/LMV924
Typical Performance Characteristics
TA = 25C. (Continued) CMRR vs. Frequency
Unless otherwise specified, VS = +5V, single supply,
PSRR vs. Frequency
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Input Voltage Noise vs. Frequency
Input Current Noise vs. Frequency
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THD vs. Frequency
THD vs. Frequency
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LMV921/LMV922/LMV924
Typical Performance Characteristics
TA = 25C. (Continued) Slew Rate vs. Supply Voltage
Unless otherwise specified, VS = +5V, single supply,
Small Signal Non-Inverting Response
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Small Signal Non-Inverting Response
Small Signal Non-Inverting Response
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Small Signal Inverting Response
Small Signal Inverting Response
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LMV921/LMV922/LMV924
Typical Performance Characteristics
TA = 25C. (Continued) Small Signal Inverting Response
Unless otherwise specified, VS = +5V, single supply,
Small Signal Non-Inverting Response
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Small Signal Non-Inverting Response
Small Signal Non-Inverting Response
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Small Signal Inverting Response
Small Signal Inverting Response
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LMV921/LMV922/LMV924
Typical Performance Characteristics
TA = 25C. (Continued) Small Signal Inverting Response
Unless otherwise specified, VS = +5V, single supply,
*Large Signal Non-Inverting Response
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*Large Signal Non-Inverting Response
*Large Signal Non-Inverting Response
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*Large Signal Inverting Response
*Large Signal Inverting Response
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LMV921/LMV922/LMV924
Typical Performance Characteristics
TA = 25C. (Continued)
*Large Signal Inverting Response
Unless otherwise specified, VS = +5V, single supply,
*Large Signal Non-Inverting Response
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*Large Signal Non-Inverting Response
*Large Signal Inverting Response
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*Large Signal Inverting Response
*Large Signal Inverting Response
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LMV921/LMV922/LMV924
Typical Performance Characteristics
TA = 25C. (Continued)
*Large Signal Inverting Response
Unless otherwise specified, VS = +5V, single supply,
Short Circuit Current vs. Temperature (sinking)
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Short Circuit Current vs. Temperature (sourcing)
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*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 25C and 85C. At -40C, input is 10mV below the positive rail and 10mV above the negative rail.
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LMV921/LMV922/LMV924
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
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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.
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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 (600 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.
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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 100k, 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. 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
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LMV921/LMV922/LMV924
Application Note
(Continued)
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. 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 600 loads. Because of the high current capability, care should be taken not to exceed the 150C 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 145A of supply current per Amplifier. A high power supply rejection ratio of 78dB allows the amplifier to be powered directly off a decaying battery voltage extending battery life.
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) 1.5 2.7 1.2 1.2 End-of-Life Voltage (V) 0.9 2.0 0.9 1.0 Capacity AA Size (mA - h) 1000 1000 375 500 LMV921 Operating time (Hours) 6802 6802 2551 3401
Alkaline Lithium Ni - Cad NMH
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LMV921/LMV922/LMV924
Typical Applications
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.
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.
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FIGURE 5. Half-Wave Rectifier with Rail-To-Ground Output Swing Referenced to Ground
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FIGURE 6. Half-Wave Rectifier with Negative-Going Output Referenced to VCC
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LMV921/LMV922/LMV924
Typical Applications
(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-
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.
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FIGURE 7. Rail-to-rail instrumentation amplifier
Simplified Schematic
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LMV921/LMV922/LMV924
Connection Diagrams
5-Pin SC70-5/SOT23-5 8-Pin MSOP/SOIC 14-Pin TSSOP/SOIC
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Top View
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Top View
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Top View
Ordering Information
Package Temperature Range Industrial -40C to +85C LMV921M7 LMV921M7X 5-Pin SOT-23 8-Pin MSOP 14-Pin TSSOP 8-Pin SOIC 14-Pin SOIC LMV921M5 LMV921M5X LMV922MM LMV922MMX LMV924MT LMV924MTX LMV922M LMV922MX LMV924M LMV924MX Package Marking Transport Media NSC Drawing MAA05A
5-Pin SC70-5
A21 A21 A29A A29A LMV922 LMV922 LMV924 LMV924 LMV922M LMV922M LMV924M LMV924M
1k 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 Rails 2.5k Units Tape and Reel Rails 2.5k Units Tape and Reel Rails 2.5k Units Tape and Reel
MF05A MUA08A MTC14 M08A M14A
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20
LMV921/LMV922/LMV924
SC70-5 Tape Dimensions
10097996
SOT23-5 and SC70-5 Tape Format Tape Format
Tape Section Leader (Start End) Carrier Trailer (Hub End)
# Cavities
0 (min) 75 (min) 3000 250 125 (min) 0 (min)
Cavity Status Empty Empty Filled Filled Empty Empty
Cover Tape Status Sealed Sealed Sealed Sealed Sealed Sealed
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LMV921/LMV922/LMV924
SOT23-5 Tape Dimensions
10097997
8 mm Tape Size
0.130 (3.3) DIM A
0.124 (3.15) DIM Ao
0.130 (3.3) DIM B
0.126 (3.2) DIM Bo
0.138 0.002 (3.5 0.05) DIM F
0.055 0.004 (1.4 0.11) DIM Ko
0.157 (4) DIM P1
0.315 0.012 (8 0.3) DIM W
SOT23-5 and SC70-5 Reel Dimensions
10097998
8 mm Tape Size
7.00 330.00 A
0.059 0.512 0.795 2.165 1.50 B 13.00 20.20 55.00 C D N
0.331 + 0.059/-0.000 8.40 + 1.50/-0.00 W1
0.567 14.40 W2
W1+ 0.078/-0.039 W1 + 2.00/-1.00 W3
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22
LMV921/LMV922/LMV924
Physical Dimensions
unless otherwise noted
inches (millimeters)
SC70-5 NS Package Number MAA05A
23
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LMV921/LMV922/LMV924
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
5-Pin SOT-23 NS Package Number MF05A
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24
LMV921/LMV922/LMV924
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
8-Pin MSOP NS Package Number MUA08A
25
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LMV921/LMV922/LMV924
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
14-Pin TSSOP NS Package Number MTC14
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26
LMV921/LMV922/LMV924
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
8-Pin SOIC NS Package Number M08A
14-Pin SOIC NS Package Number MA14
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LMV921/LMV922/LMV924 Single, Dual and Quad 1.8V, 1MHz, Low Power Operational Amplifiers with Rail-To-Rail Input and Output
Notes
LIFE SUPPORT POLICY NATIONAL'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.
National Semiconductor Corporation Americas Email: support@nsc.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Francais Tel: +33 (0) 1 41 91 8790
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: ap.support@nsc.com
National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507
www.national.com
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.

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