LMV791MK-NS

National Semiconductor is now part of Texas Instruments. Search http://www.ti.com/ for the latest technical information and details on our current products and services. LMV791/LMV792 17 MHz, Low Noise, CMOS Input, 1.8V Operational Amplifiers with Shutdown General Description Features The LMV791 (Single) and the LMV792 (Dual) low noise, CMOS input operational amplifiers offer a low input voltage while consuming only 1.15 mA noise density of 5.8 nV/ (LMV791) of quiescent current. The LMV791 and LMV792 are unity gain stable op amps and have gain bandwidth of 17 MHz. The LMV791/ LMV792 have a supply voltage range of 1.8V to 5.5V and can operate from a single supply. The LMV791/LMV792 each feature a rail-to-rail output stage capable of driving a 600Ω load and sourcing as much as 60 mA of current. The LMV791 family provides optimal performance in low voltage and low noise systems. A CMOS input stage, with typical input bias currents in the range of a few femtoAmperes, and an input common mode voltage range which includes ground make the LMV791 and the LMV792 ideal for low power sensor applications. The LMV791 family has a built-in enable feature which can be used to optimize power dissipation in low power applications. The LMV791/LMV792 are manufactured using National’s advanced VIP50 process and are offered in a 6-pin TSOT23 and a 10-pin MSOP package respectively. (Typical 5V supply, unless otherwise noted) 5.8 nV/√Hz ■ Input referred voltage noise 100 fA ■ Input bias current 17 MHz ■ Unity gain bandwidth ■ Supply current per channel enable mode 1.15 mA — LMV791 1.30 mA — LMV792 ■ Supply current per channel in shutdown mode 0.02 µA ■ Rail-to-rail output swing 25 mV from rail — @ 10 kΩ load 45 mV from rail — @ 2 kΩ load ■ Guaranteed 2.5V and 5.0V performance 0.01% @1 kHz, 600Ω ■ Total harmonic distortion −40°C to 125°C ■ Temperature range Applications ■ ■ ■ ■ ■ Photodiode amplifiers Active filters and buffers Low noise signal processing Medical Instrumentation Sensor interface applications Typical Application 20116869 Photodiode Transimpedance Amplifier © 2008 National Semiconductor Corporation 201168 20116839 Input Referred Voltage Noise vs. Frequency www.national.com LMV791/LMV792 17 MHz, Low Noise, CMOS Input, 1.8V Operational Amplifiers with Shutdown June 23, 2008 LMV791/LMV792 Absolute Maximum Ratings (Note 1) Soldering Information If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.  Infrared or Convection (20 sec)  Wave Soldering Lead Temp (10 sec) ESD Tolerance (Note 2)  Human Body Model  Machine Model  Charge-Device Model VIN Differential Supply Voltage (V+ – V−) Input/Output Pin Voltage Storage Temperature Range Junction Temperature (Note 3) Operating Ratings 2000V 1000V ±0.3V 6.0V V+ +0.3V, V− −0.3V −65°C to 150°C +150°C 260°C (Note 1) Temperature Range (Note 3) Supply Voltage (V+ – V−)  −40°C ≤ TA ≤ 125°C 200V 235°C −40°C to 125°C 2.0V to 5.5V   0°C ≤ TA ≤ 125°C 1.8V to 5.5V Package Thermal Resistance (θJA (Note 3))  6-Pin TSOT23  10-Pin MSOP 170°C/W 236°C/W 2.5V Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TA = 25°C, V+ = 2.5V, V− = 0V, VCM = V+/2 = VO, VEN = V+. Boldface limits apply at the temperature extremes. Symbol VOS Parameter Conditions Min Typ Max (Note 5) (Note 4) (Note 5) Input Offset Voltage 0.1 TC VOS Input Offset Voltage Temperature Drift LMV791 (Note 6) −1.0 LMV792 (Note 6) −1.8 IB Input Bias Current VCM = 1.0V (Notes 7, 8) 0.05 1 25 −40°C ≤ TA ≤ 85 °C 0.05 1 100 Input Offset Current VCM = 1.0V (Note 8) CMRR Common Mode Rejection Ratio 0V ≤ VCM ≤ 1.4V 80 75 94 PSRR Power Supply Rejection Ratio 2.0V ≤ V+ ≤ 5.5V, VCM = 0V 80 75 100 1.8V ≤ V+ ≤ 5.5V, VCM = 0V 80 98 Common Mode Voltage Range 10 CMRR ≥ 60 dB AVOL Open Loop Voltage Gain VOUT = 0.15V to 2.2V, LMV791 RLOAD = 2 kΩ to V+/2 LMV792 VOUT = 0.15V to 2.2V, RLOAD = 10 kΩ to V+/2 VOUT Output Voltage Swing High Output Voltage Swing Low www.national.com fA dB 1.5 1.5 85 80 98 82 78 92 88 84 110 V dB RLOAD = 2 kΩ to V+/2 25 75 82 RLOAD = 10 kΩ to V+/2 20 65 71 RLOAD = 2 kΩ to V+/2 30 75 78 RLOAD = 10 kΩ to V+/2 15 65 67 2 pA dB −0.3 −0.3 CMRR ≥ 55 dB mV μV/°C −40°C ≤ TA ≤ 85 °C IOS CMVR ±1.35 ±1.65 Units mV from either rail IOUT IS Parameter Output Current Supply Current per Amplifier Conditions Min Typ Max (Note 5) (Note 4) (Note 5) Sourcing to V− VIN = 200 mV (Note 9) 35 28 47 Sinking to V+ VIN = –200 mV (Note 9) 7 5 15 Enable Mode SR Slew Rate mA LMV791 0.95 1.30 1.65 LMV792 per channel 1.1 1.50 1.85 Shutdown Mode, VEN < 0.4 per channel 0.02 1 5 AV = +1, Rising (10% to 90%) 8.5 AV = +1, Falling (90% to 10%) 10.5 VEN ≥ 2.1V Units mA μA V/μs GBW Gain Bandwidth 14 en Input Referred Voltage Noise Density f = 1 kHz 6.2 nV/ in Input Referred Current Noise Density f = 1 kHz 0.01 pA/ ton Turn-on Time 140 ns toff Turn-off Time 1000 ns VEN Enable Pin Voltage Range Enable Mode 2.1 Shutdown Mode IEN Enable Pin Input Current THD+N Total Harmonic Distortion + Noise MHz 2 to 2.5 0 to 0.5 0.4 Enable Mode VEN = 2.5V (Note 7) 1.5 3 Shutdown Mode VEN = 0V (Note 7) 0.003 0.1 f = 1 kHz, AV = 1, RLOAD = 600Ω 0.01 V μA % 5V Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TA = 25°C, V+ = 5V, V− = 0V, VCM = V+/2 = VO, VEN = V+. Boldface limits apply at the temperature extremes. Symbol VOS Parameter Conditions Min Typ Max (Note 5) (Note 4) (Note 5) Input Offset Voltage 0.1 TC VOS Input Offset Voltage Temperature Drift LMV791 (Note 6) −1.0 LMV792 (Note 6) −1.8 IB Input Bias Current VCM = 2.0V (Notes 7, 8) 0.1 1 25 −40°C ≤ TA ≤ 125°C 0.1 1 100 Input Offset Current VCM = 2.0V (Note 8) CMRR Common Mode Rejection Ratio 0V ≤ VCM ≤ 3.7V 80 75 100 PSRR Power Supply Rejection Ratio 2.0V ≤ V+ ≤ 5.5V, VCM = 0V 80 75 100 1.8V ≤ V+ ≤ 5.5V, VCM = 0V 80 98 Common Mode Voltage Range 10 CMRR ≥ 60 dB −0.3 −0.3 CMRR ≥ 55 dB 3 mV μV/°C −40°C ≤ TA ≤ 85°C IOS CMVR ±1.35 ±1.65 Units pA fA dB dB 4 4 V www.national.com LMV791/LMV792 Symbol LMV791/LMV792 AVOL Open Loop Voltage Gain VOUT = 0.3V to 4.7V, LMV791 RLOAD = 2 kΩ to V+/2 LMV792 VOUT = 0.3V to 4.7V, RLOAD = 10 kΩ to V+/2 VOUT Output Voltage Swing High Output Voltage Swing Low 85 80 97 82 78 89 88 84 110 RLOAD = 2 kΩ to V+/2 35 75 82 RLOAD = 10 kΩ to V+/2 25 65 71 RLOAD = 2 kΩ to V+/2 LMV791 42 75 78 LMV792 45 80 83 20 65 67 RLOAD = 10 kΩ to V+/2 IOUT IS Output Current Supply Current per Amplifier Sourcing to V− VIN = 200 mV (Note 9) 45 37 60 Sinking to V+ VIN = –200 mV (Note 9) 10 6 21 Enable Mode 1.15 1.40 1.75 LMV792 per channel 1.30 1.70 2.05 0.14 1 5 Shutdown Mode (VEN ≤ 0.4V) Slew Rate AV = +1, Rising (10% to 90%) 6.0 9.5 AV = +1, Falling (90% to 10%) 7.5 11.5 mV from either rail mA LMV791 VEN ≥ 4.6V SR dB mA μA V/μs GBW Gain Bandwidth en Input Referred Voltage Noise Density f = 1 kHz 5.8 17 nV/ in Input Referred Current Noise Density f = 1 kHz 0.01 pA/ ton Turn-on Time toff Turn-off Time VEN Enable Pin Voltage Range Enable Mode 4.6 Shutdown Mode IEN Enable Pin Input Current THD+N Total Harmonic Distortion + Noise MHz 110 ns 800 ns 4.5 to 5 0 to 0.5 0.4 Enable Mode VEN = 5.0V (Note 7) 5.6 10 Shutdown Mode VEN = 0V (Note 7) 0.005 0.2 f = 1 kHz, AV = 1, RLOAD = 600Ω 0.01 V μA % 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 Tables. Note 2: Human Body Model is 1.5 kΩ in series with 100 pF. Machine Model is 0Ω in series with 200 pF Note 3: The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) - TA)/θJA. All numbers apply for packages soldered directly onto a PC Board. Note 4: Typical values represent the parametric norm at the time of characterization. Note 5: Limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlations using the statistical quality control (SQC) method. Note 6: Offset voltage average drift is determined by dividing the change in VOS by temperature change. Note 7: Positive current corresponds to current flowing into the device. Note 8: This parameter is guaranteed by design and/or characterization and is not tested in production. Note 9: The short circuit test is a momentary test, the short circuit duration is 1.5 ms. www.national.com 4 LMV791/LMV792 Connection Diagrams 6-Pin TSOT23 10-Pin MSOP 20116801 Top View 20116802 Top View Ordering Information Package 6-Pin TSOT23 10-Pin MSOP Part Number LMV791MK LMV791MKX LMV792MM LMV792MMX Package Marking Transport Media 1k Units Tape and Reel AS1A 3k Units Tape and Reel 1k Units Tape and Reel AX2A 3.5k Units Tape and Reel 5 NSC Drawing MK06A MUB10A www.national.com LMV791/LMV792 Typical Performance Characteristics Unless otherwise specified, TA = 25°C, V– = 0, V+ = Supply Voltage = 5V, VCM = V+/2, VEN = V+. Supply Current vs. Supply Voltage (LMV791) Supply Current vs. Supply Voltage (LMV792) 20116805 20116881 Supply Current vs. Supply Voltage in Shutdown Mode VOS vs. VCM 20116806 20116809 VOS vs. VCM VOS vs. VCM 20116811 20116851 www.national.com 6 LMV791/LMV792 VOS vs. Supply Voltage Slew Rate vs. Supply Voltage 20116829 20116812 Supply Current vs. Enable Pin Voltage (LMV791) Supply Current vs. Enable Pin Voltage(LMV791) 20116807 20116808 Supply Current vs. Enable Pin Voltage (LMV792) Supply Current vs. Enable Pin Voltage (LMV792) 20116882 20116883 7 www.national.com LMV791/LMV792 Input Bias Current vs. VCM Input Bias Current vs. VCM 20116887 20116862 Sourcing Current vs. Supply Voltage Sinking Current vs. Supply Voltage 20116820 20116819 Sourcing Current vs. Output Voltage Sinking Current vs. Output Voltage 20116850 www.national.com 20116854 8 Negative Output Swing vs. Supply Voltage 20116817 20116815 Positive Output Swing vs. Supply Voltage Negative Output Swing vs. Supply Voltage 20116816 20116814 Positive Output Swing vs. Supply Voltage Negative Output Swing vs. Supply Voltage 20116813 20116818 9 www.national.com LMV791/LMV792 Positive Output Swing vs. Supply Voltage LMV791/LMV792 Input Referred Voltage Noise vs. Frequency Time Domain Voltage Noise 20116831 20116839 Overshoot and Undershoot vs. CLOAD THD+N vs. Peak-to-Peak Output Voltage (VOUT) 20116826 20116830 THD+N vs. Peak-to-Peak Output Voltage (VOUT) THD+N vs. Frequency 20116874 20116804 www.national.com 10 Open Loop Gain and Phase with Capacitive Load 20116875 20116841 Open Loop Gain and Phase with Resistive Load Closed Loop Output Impedance vs. Frequency 20116832 20116873 Crosstalk Rejection Small Signal Transient Response, AV = +1 20116838 20116880 11 www.national.com LMV791/LMV792 THD+N vs. Frequency LMV791/LMV792 Large Signal Transient Response, AV = +1 Small Signal Transient Response, AV = +1 20116837 20116833 Large Signal Transient Response, AV = +1 Phase Margin vs. Capacitive Load (Stability) 20116834 20116845 Phase Margin vs. Capacitive Load (Stability) Positive PSRR vs. Frequency 20116846 www.national.com 20116827 12 LMV791/LMV792 Negative PSRR vs. Frequency CMRR vs. Frequency 20116856 20116828 Input Common Mode Capacitance vs. VCM 20116876 13 www.national.com LMV791/LMV792 Small Size The small footprint of the LMV791 and the LMV792 package saves space on printed circuit boards, and enables the design of smaller electronic products, such as cellular phones, pagers, or other portable systems. Long traces between the signal source and the opamp make the signal path susceptible to noise. By using a physically smaller LMV791 and LMV792 package, the opamp can be placed closer to the signal source, reducing noise pickup and increasing signal integrity. Application Information ADVANTAGES OF THE LMV791/LMV792 Wide Bandwidth at Low Supply Current The LMV791 and LMV792 are high performance op amps that provide a unity gain bandwidth of 17 MHz while drawing a low supply current of 1.15 mA. This makes them ideal for providing wideband amplification in portable applications. The enable and shutdown feature can also be used to design more power efficient systems that offer wide bandwidth and high performance while consuming less average power. CAPACITIVE LOAD TOLERANCE The LMV791 and LMV792 can directly drive 120 pF in unitygain without oscillation. The unity-gain follower is the most sensitive configuration to capacitive loading. Direct capacitive loading reduces the phase margin of amplifiers. 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. To drive a heavier capacitive load, the circuit in Figure 1 can be used. In Figure 1, the isolation resistor RISO and the load capacitor CL form a pole to increase stability by adding more phase margin to the overall system. The desired performance depends on the value of RISO. The bigger the RISO resistor value, the more stable VOUT will be. Increased RISO would, however, result in a reduced output swing and short circuit current. Low Input Referred Noise and Low Input Bias Current The LMV791/LMV792 have a very low input referred voltage at 1 kHz). A CMOS input stage ennoise density (5.8 nV/ sures a small input bias current (100 fA) and low input referred ). This is very helpful in maintaincurrent noise (0.01 pA/ ing signal fidelity, and makes the LMV791 and LMV792 ideal for audio and sensor based applications. Low Supply Voltage The LMV791 and the LMV792 have performance guaranteed at 2.5V and 5V supply. The LMV791 family is guaranteed to be operational at all supply voltages between 2.0V and 5.5V, for ambient temperatures ranging from −40°C to 125°C, thus utilizing the entire battery lifetime. The LMV791 and LMV792 are also guaranteed to be operational at 1.8V supply voltage, for temperatures between 0°C and 125°C. This makes the LMV791 family ideal for usage in low-voltage commercial applications. RRO and Ground Sensing Rail-to-rail output swing provides maximum possible dynamic range at the output. This is particularly important when operating at low supply voltages. An innovative positive feedback scheme is used to boost the current drive capability of the output stage. This allows the LMV791 and the LMV792 to source more than 40 mA of current at 1.8V supply. This also limits the performance of the LMV791 family as comparators, and hence the usage of the LMV791 and the LMV792 in an open-loop configuration is not recommended. The input common-mode range includes the negative supply rail which allows direct sensing at ground in single supply operation. 20116861 FIGURE 1. Isolation of CL to Improve Stability INPUT CAPACITANCE AND FEEDBACK CIRCUIT ELEMENTS The LMV791 family has a very low input bias current (100 fA) and a low 1/f noise corner frequency (400 Hz), which makes it ideal for sensor applications. However, to obtain this performance a large CMOS input stage is used, which adds to the input capacitance of the op-amp, CIN. Though this does not affect the DC and low frequency performance, at higher frequencies the input capacitance interacts with the input and the feedback impedances to create a pole, which results in lower phase margin and gain peaking. This can be controlled by being selective in the use of feedback resistors, as well as by using a feedback capacitance, CF. For example, in the inverting amplifier shown in Figure 2, if CIN and CF are ignored and the open loop gain of the op amp is considered infinite then the gain of the circuit is −R2/R1. An op amp, however, usually has a dominant pole, which causes its gain to drop with frequency. Hence, this gain is only valid for DC and low frequency. To understand the effect of the input capacitance coupled with the non-ideal gain of the op amp, the circuit needs to be analyzed in the frequency domain using a Laplace transform. Enable and Shutdown Features The LMV791 family is ideal for battery powered systems. With a low supply current of 1.15 mA and a shutdown current of 140 nA typically, the LMV791 and LMV792 allow the designer to maximize battery life. The enable pin of the LMV791 and the LMV792 allows the op amp to be turned off and reduce its supply current to less than 1 μA. To power on the op amp the enable pin should be higher than V+ - 0.5V, where V+ is the positive supply. To disable the op amp, the enable pin voltage should be less than V− + 0.5V, where V− is the negative supply. www.national.com 14 LMV791/LMV792 20116864 FIGURE 2. Inverting Amplifier 20116859 For simplicity, the op amp is modelled as an ideal integrator with a unity gain frequency of A0 . Hence, its transfer function (or gain) in the frequency domain is A0/s. Solving the circuit equations in the frequency domain, ignoring CF for the moment, results in an expression for the gain shown in Equation 1. FIGURE 3. Gain Peaking Caused by Large R1, R2 A way of reducing the gain peaking is by adding a feedback capacitance CF in parallel with R2. This introduces another pole in the system and prevents the formation of pairs of complex conjugate poles which cause the gain to peak. Figure 4 shows the effect of CF on the frequency response of the circuit. Adding a capacitance of 2 pF removes the peak, while a capacitance of 5 pF creates a much lower pole and reduces the bandwidth excessively. (1) It can be inferred from the denominator of the transfer function that it has two poles, whose expressions can be obtained by solving for the roots of the denominator and are shown in Equation 2. (2) Equation 2 shows that as the values of R1 and R2 are increased, the magnitude of the poles, and hence the bandwidth of the amplifier, is reduced. This theory is verified by using different values of R1 and R2 in the circuit shown in Figure 1 and by comparing their frequency responses. In Figure 3 the frequency responses for three different values of R1 and R2 are shown. When both R1 and R2 are 1 kΩ, the response is flattest and widest; whereas, it narrows and peaks significantly when both their values are changed to 10 kΩ or 30 kΩ. So it is advisable to use lower values of R1 and R2 to obtain a wider and flatter response. Lower resistances also help in high sensitivity circuits since they add less noise. 20116860 FIGURE 4. Gain Peaking Eliminated by CF 15 www.national.com LMV791/LMV792 AUDIO PREAMPLIFIER WITH BANDPASS FILTERING With low input referred voltage noise, low supply voltage and low supply current, and a low harmonic distortion, the LMV791 family is ideal for audio applications. Its wide unity gain bandwidth allows it to provide large gain for a wide range of frequencies and it can be used to design a preamplifier to drive a load of as low as 600Ω with less than 0.01% distortion. Two amplifier circuits are shown in Figure 5 and Figure 6. Figure 5 is an inverting amplifier, with a 10 kΩ feedback resistor, R2, and a 1kΩ input resistor, R1, and hence provides a gain of −10. Figure 6 is a non-inverting amplifier, using the same values of R1and R2, and provides a gain of 11. In either of these circuits, the coupling capacitor CC1 decides the lower frequency at which the circuit starts providing gain, while the feedback capacitor CF decides the frequency at which the gain starts dropping off. Figure 7 shows the frequency response of the inverting amplifier with different values of CF. 20116858 FIGURE 7. Frequency Response of the Inverting Audio Preamplifier TRANSIMPEDANCE AMPLIFIER CMOS input op amps are often used in transimpedance applications as they have an extremely high input impedance. A transimpedance amplifier converts a small input current into a voltage. This current is usually generated by a photodiode. The transimpedance gain, measured as the ratio of the output voltage to the input current, is expected to be large and wideband. Since the circuit deals with currents in the range of a few nA, low noise performance is essential. The LMV791/ LMV792 are CMOS input op amps providing wide bandwidth and low noise performance, and are hence ideal for transimpedance applications. Usually, a transimpedance amplifier is designed on the basis of the current source driving the input. A photodiode is a very common capacitive current source, which requires transimpedance gain for transforming its miniscule current into easily detectable voltages. The photodiode and amplifier’s gain are selected with respect to the speed and accuracy required of the circuit. A faster circuit would require a photodiode with lesser capacitance and a faster amplifier. A more sensitive circuit would require a sensitive photodiode and a high gain. A typical transimpedance amplifier is shown in Figure 8. The output voltage of the amplifier is given by the equation VOUT = −IINRF. Since the output swing of the amplifier is limited, RF should be selected such that all possible values of IIN can be detected. The LMV791/LMV792 have a large gain-bandwidth product (17 MHz), which enables high gains at wide bandwidths. A rail-to-rail output swing at 5.5V supply allows detection and amplification of a wide range of input currents. A CMOS input stage with negligible input current noise and low input voltage noise allows the LMV791/LMV792 to provide high fidelity amplification for wide bandwidths. These properties make the LMV791/LMV792 ideal for systems requiring wide-band transimpedance amplification. 20116865 FIGURE 5. Inverting Audio Preamplifier 20116866 FIGURE 6. Non-inverting Audio Preamplifier www.national.com 16 LMV791/LMV792 20116884 FIGURE 9. CF Selection for Stability 20116869 FIGURE 8. Photodiode Transimpedance Amplifier Calculating CF from Equation 3 can sometimes return unreasonably small values (