LMC6464AMN

LMC6462 Dual/LMC6464 Quad Micropower, Rail-to-Rail Input and Output CMOS Operational Amplifier May 1999 LMC6462 Dual/LMC6464 Quad Micropower, Rail-to-Rail Input and Output CMOS Operational Amplifier General Description The LMC6462/4 is a micropower version of the popular LMC6482/4, combining Rail-to-Rail Input and Output Range with very low power consumption. The LMC6462/4 provides an input common-mode voltage range that exceeds both rails. The rail-to-rail output swing of the amplifier, guaranteed for loads down to 25 kΩ, assures maximum dynamic sigal range. This rail-to-rail performance of the amplifier, combined with its high voltage gain makes it unique among rail-to-rail amplifiers. The LMC6462/4 is an excellent upgrade for circuits using limited common-mode range amplifiers. The LMC6462/4, with guaranteed specifications at 3V and 5V, is especially well-suited for low voltage applications. A quiescent power consumption of 60 µW per amplifier (at VS = 3V) can extend the useful life of battery operated systems. The amplifier’s 150 fA input current, low offset voltage of 0.25 mV, and 85 dB CMRR maintain accuracy in battery-powered systems. Features (Typical unless otherwise noted) n Ultra Low Supply Current 20 µA/Amplifier n Guaranteed Characteristics at 3V and 5V n Rail-to-Rail Input Common-Mode Voltage Range n Rail-to-Rail Output Swing (within 10 mV of rail, VS = 5V and RL = 25 kΩ) n Low Input Current 150 fA n Low Input Offset Voltage 0.25 mV Applications n n n n n Battery Operated Circuits Transducer Interface Circuits Portable Communication Devices Medical Applications Battery Monitoring 8-Pin DIP/SO 14-Pin DIP/SO DS012051-1 Top View DS012051-2 Top View © 1999 National Semiconductor Corporation DS012051 www.national.com Ordering Information Package Military −55˚C to +125˚C 8-Pin Molded DIP 8-Pin SO-8 14-Pin Molded DIP 14-Pin SO-14 8-Pin Ceramic DIP 14-Pin Ceramic DIP 14-Pin Ceramic SOIC LMC6462AMJ-QML LMC6464AMJ-QML LMC6464AMWG-QML LMC6464AMN LMC6462AMN Temperature Range Industrial −40˚C to +85˚C LMC6462AIN, LMC6462BIN LMC6462AIM, LMC6462BIM LMC6462AIMX, LMC6462BIMX LMC6464AIN, LMC6464BIN LMC6464AIM, LMC6464BIM LMC6464AIMX, LMC6464BIMX N08E M08A M08A N14A M14A M14A J08A J14A WG14A Rails Rails Tape and Reel Rails Rails Tape and Reel Rails Rails Trays NSC Drawing Transport Media www.national.com 2 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 2) Differential Input Voltage Voltage at Input/Output Pin Supply Voltage (V+ − V−) Current at Input Pin (Note 12) Current at Output Pin (Notes 3, 8) Current at Power Supply Pin Lead Temp. (Soldering, 10 sec.) Storage Temperature Range Junction Temperature (Note 4) 2.0 kV ± Supply Voltage (V+) + 0.3V, (V−) − 0.3V 16V ± 5 mA Operating Ratings (Note 1) 3.0V ≤ V+ ≤ 15.5V −55˚C ≤ TJ ≤ +125˚C −40˚C ≤ TJ ≤ +85˚C −40˚C ≤ TJ ≤ +85˚C 115˚C/W 193˚C/W 81˚C/W 126˚C/W ± 30 mA 40 mA 260˚C −65˚C to +150˚C 150˚C Supply Voltage Junction Temperature Range LMC6462AM, LMC6464AM LMC6462AI, LMC6464AI LMC6462BI, LMC6464BI Thermal Resistance (θJA) N Package, 8-Pin Molded DIP M Package, 8-Pin Surface Mount N Package, 14-Pin Molded DIP M Package, 14-Pin Surface Mount 5V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = 5V, V− = 0V, VCM = VO = V+/2 and RL > 1M. Boldface limits apply at the temperature extremes. LMC6462AI Symbol Parameter Conditions Typ (Note 5) VOS TCVOS IB IOS CIN RIN CMRR Input Offset Voltage Input Offset Voltage Average Drift Input Current Input Offset Current Common-Mode Input Capacitance Input Resistance Common Mode Rejection Ratio 0V ≤ VCM ≤ 15.0V, V+ = 15V 0V ≤ VCM ≤ 5.0V V+ = 5V +PSRR −PSRR VCM Positive Power Supply Rejection Ratio Negative Power Supply Rejection Ratio Input Common-Mode Voltage Range 5V ≤ V+ ≤ 15V, V− = 0V, VO = 2.5V −5V ≤ V− ≤ −15V, V+ = 0V, VO = −2.5V V+ = 5V For CMRR ≥ 50 dB 5.30 V+ = 15V For CMRR ≥ 50 dB 15.30 −0.2 (Note 13) (Note 13) 0.15 0.075 3 10 5 10 5 200 100 pA max pA max pF Tera Ω 70 67 85 85 85 −0.2 70 67 70 67 70 67 −0.10 0.00 5.25 5.00 −0.15 0.00 15.25 15.00 65 62 65 62 65 62 65 62 −0.10 0.00 5.25 5.00 −0.15 0.00 15.25 15.00 70 65 70 65 70 65 70 65 −0.10 0.00 5.25 5.00 −0.15 0.00 15.25 15.00 dB min dB min V max V min V max V min dB min 0.25 1.5 LMC6464AI Limit (Note 6) 0.5 1.2 LMC6462BI LMC6464BI Limit (Note 6) 3.0 3.7 LMC6462AM LMC6464AM Limit (Note 6) 0.5 1.5 mV max µV/˚C Units > 10 85 3 www.national.com 5V DC Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = 5V, V− = 0V, VCM = VO = V+/2 and RL > 1M. Boldface limits apply at the temperature extremes. LMC6462AI Symbol Parameter Conditions Typ (Note 5) AV Large Signal Voltage Gain RL = 100 kΩ (Note 7) Sinking RL = 25 kΩ (Note 7) Sinking VO Output Swing V+ = 5V RL = 100 kΩ to V+/2 200 4.995 0.005 V+ = 5V RL = 25 kΩ to V+/2 4.990 0.010 V+ = 15V RL = 100 kΩ to V+/2 14.990 0.010 V+ = 15V RL = 25 kΩ to V+/2 14.965 0.025 ISC Output Short Circuit Current V+ = 5V ISC Output Short Circuit Current V+ = 15V IS Supply Current Sourcing, VO = 0V Sinking, VO = 5V Sourcing, VO = 0V Sinking, VO = 12V (Note 8) Dual, LMC6462 V+ = +5V, VO = V+/2 Quad, LMC6464 V+ = +5V, VO = V+/2 Dual, LMC6462 V+ = +15V, VO = V+/2 Quad, LMC6464 V+ = +15V, VO = V+/2 40 80 50 90 27 27 38 75 4.990 4.980 0.010 0.020 4.975 4.965 0.020 0.035 14.975 14.965 0.025 0.035 14.900 14.850 0.050 0.150 19 15 22 17 24 17 55 45 55 70 110 140 60 70 120 140 4.950 4.925 0.050 0.075 4.950 4.850 0.050 0.150 14.950 14.925 0.050 0.075 14.850 14.800 0.100 0.200 19 15 22 17 24 17 55 45 55 70 110 140 60 70 120 140 4.990 4.970 0.010 0.030 4.975 4.955 0.020 0.045 14.975 14.955 0.025 0.050 14.900 14.800 0.050 0.200 19 15 22 17 24 17 55 45 55 75 110 150 60 75 120 150 Sourcing 400 2500 Sourcing 3000 LMC6464AI Limit (Note 6) LMC6462BI LMC6464BI Limit (Note 6) LMC6462AM LMC6464AM Limit (Note 6) V/mV min V/mV min V/mV min V/mV min V min V max V min V max V min V max V min V max mA min mA min mA min mA min µA max µA max µA max µA max Units www.national.com 4 5V AC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = 5V, V− = 0V, VCM = VO = V+/2 and RL > 1M. Boldface limits apply at the temperature extremes. LMC6462AI Symbol Parameter Conditions Typ (Note 5) SR GBW φm Gm en in Slew Rate Gain-Bandwidth Product Phase Margin Gain Margin Amp-to-Amp Isolation Input-Referred Voltage Noise Input-Referred Current Noise (Note 10) f = 1 kHz VCM = 1V f = 1 kHz (Note 9) V+ = 15V 28 50 50 15 130 80 0.03 LMC6464AI Limit (Note 6) 15 8 LMC6462BI LMC6464BI Limit (Note 6) 15 8 LMC6462AM LMC6464AM Limit (Note 6) 15 8 V/ms min kHz Deg dB dB Units 3V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = 3V, V− = 0V, VCM = VO = V+/2 and RL > 1M. Boldface limits apply at the temperature extremes. LMC6462AI Symbol Parameter Conditions Typ (Note 5) VOS TCVOS IB IOS CMRR PSRR VCM Input Offset Voltage Input Offset Voltage Average Drift Input Current Input Offset Current Common Mode Rejection Ratio Power Supply Rejection Ratio Input Common-Mode Voltage Range 3.0 VO Output Swing RL = 25 kΩ to V+/2 2.95 0.15 IS Supply Current Dual, LMC6462 VO = V+/2 Quad, LMC6464 VO = V+/2 40 80 3.0 2.9 0.1 55 70 110 140 3.0 2.9 0.1 55 70 110 140 3.0 2.9 0.1 55 70 110 140 µA max For CMRR ≥ 50 dB −0.10 0.0 0.0 0.0 3V ≤ V+ ≤ 15V, V− = 0V 80 60 60 60 (Note 13) (Note 13) 0V ≤ VCM ≤ 3V 0.15 0.075 74 10 5 60 10 5 60 200 100 60 pA pA dB min dB min V max V min V min V max µA 0.9 2.0 LMC6464AI Limit (Note 6) 2.0 2.7 LMC6462BI LMC6464BI Limit (Note 6) 3.0 3.7 LMC6462AM LMC6464AM Limit (Note 6) 2.0 3.0 mV max µV/˚C Units 5 www.national.com 3V AC Electrical Characteristics Unless otherwise specified, V+ = 3V, V− = 0V, VCM = VO = V+/2 and RL > 1M. Boldface limits apply at the temperature extremes. LMC6462AI Symbol Parameter Conditions Typ (Note 5) SR GBW Slew Rate Gain-Bandwidth Product (Note 11) 23 50 LMC6464AI Limit (Note 6) LMC6462BI LMC6464BI Limit (Note 6) LMC6462AM LMC6464AM Limit (Note 6) V/ms kHz Units 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. All pins rated per method 3015.6 of MIL-STD-883. This is a class 2 device rating. 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 ± 30 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) − TA)/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+ = 15V, VCM = 7.5V and RL connected to 7.5V. For Sourcing tests, 7.5V ≤ VO ≤ 11.5V. For Sinking tests, 3.5V ≤ VO ≤ 7.5V. Note 8: Do not short circuit output to V+, when V+ is greater than 13V or reliability will be adversely affected. Note 9: V+ = 15V. Connected as Voltage Follower with 10V step input. Number specified is the slower of either the positive or negative slew rates. Note 10: Input referred, V+ = 15V and RL = 100 kΩ connected to 7.5V. Each amp excited in turn with 1 kHz to produce VO = 12 VPP. Note 11: Connected as Voltage Follower with 2V step input. Number specified is the slower of either the positive or negative slew rates. Note 12: Limiting input pin current is only necessary for input voltages that exceed absolute maximum input voltage ratings. Note 13: Guaranteed limits are dictated by tester limitations and not device performance. Actual performance is reflected in the typical value. Note 14: For guaranteed Military Temperature Range parameters see RETSMC6462/4X. Typical Performance Characteristics Supply Current vs Supply Voltage VS = +5V, Single Supply, TA = 25˚C unless otherwise specified Sourcing Current vs Output Voltage Sourcing Current vs Output Voltage DS012051-30 DS012051-31 DS012051-32 Sourcing Current vs Output Voltage Sinking Current vs Output Voltage Sinking Current vs Output Voltage DS012051-33 DS012051-34 DS012051-35 www.national.com 6 Typical Performance Characteristics specified (Continued) Sinking Current vs Output Voltage VS = +5V, Single Supply, TA = 25˚C unless otherwise Input Voltage Noise vs Frequency Input Voltage Noise vs Input Voltage DS012051-36 DS012051-37 DS012051-38 Input Voltage Noise vs Input Voltage Input Voltage Noise vs Input Voltage ∆VOS vs CMR DS012051-41 DS012051-39 DS012051-40 Input Voltage vs Output Voltage Open Loop Frequency Response Open Loop Frequency Response vs Temperature DS012051-43 DS012051-42 DS012051-44 7 www.national.com Typical Performance Characteristics specified (Continued) Gain and Phase vs Capacitive Load Slew Rate vs Supply Voltage VS = +5V, Single Supply, TA = 25˚C unless otherwise Non-Inverting Large Signal Pulse Response DS012051-45 DS012051-46 DS012051-47 Non-Inverting Large Signal Pulse Response Non-Inverting Large Signal Pulse Response Non-Inverting Small Signal Pulse Response DS012051-48 DS012051-49 DS012051-50 Non-Inverting Small Signal Pulse Response Non-Inverting Small Signal Pulse Response Inverting Large Signal Pulse Response DS012051-51 DS012051-52 DS012051-53 www.national.com 8 Typical Performance Characteristics specified (Continued) Inverting Large Signal Pulse Response VS = +5V, Single Supply, TA = 25˚C unless otherwise Inverting Large Signal Pulse Response Inverting Small Signal Pulse Response DS012051-54 DS012051-55 DS012051-56 Inverting Small Signal Pulse Response Inverting Small Signal Pulse Response DS012051-57 DS012051-58 Application Information 1.0 Input Common-Mode Voltage Range The LMC6462/4 has a rail-to-rail input common-mode voltage range. Figure 1 shows an input voltage exceeding both supplies with no resulting phase inversion on the output. pins, possibly affecting reliability. The input current can be externally limited to ± 5 mA, with an input resistor, as shown in Figure 3. DS012051-6 DS012051-5 FIGURE 2. A ± 7.5V Input Signal Greatly Exceeds the 3V Supply in Figure 3 Causing No Phase Inversion Due to RI FIGURE 1. An Input Voltage Signal Exceeds the LMC6462/4 Power Supply Voltage with No Output Phase Inversion The absolute maximum input voltage at V+ = 3V is 300 mV beyond either supply rail at room temperature. Voltages greatly exceeding this absolute maximum rating, as in Figure 2, can cause excessive current to flow in or out of the input 9 www.national.com Application Information (Continued) DS012051-7 FIGURE 3. Input Current Protection for Voltages Exceeding the Supply Voltage 2.0 Rail-to-Rail Output The approximated output resistance of the LMC6462/4 is 180Ω sourcing, and 130Ω sinking at VS = 3V, and 110Ω sourcing and 83Ω sinking at VS = 5V. The maximum output swing can be estimated as a function of load using the calculated output resistance. 3.0 Capacitive Load Tolerance The LMC6462/4 can typically drive a 200 pF load with VS = 5V at unity gain without oscillating. The unity gain follower is the most sensitive configuration to capacitive load. Direct capacitive loading reduces the phase margin of op-amps. The combination of the op-amp’s output impedance and the capacitive load induces phase lag. This results in either an underdamped pulse response or oscillation. Capacitive load compensation can be accomplished using resistive isolation as shown in Figure 4. If there is a resistive component of the load in parallel to the capacitive component, the isolation resistor and the resistive load create a voltage divider at the output. This introduces a DC error at the output. Another circuit, shown in Figure 6, is also used to indirectly drive capacitive loads. This circuit is an improvement to the circuit shown in Figure 4 because it provides DC accuracy as well as AC stability. R1 and C1 serve to counteract the loss of phase margin by feeding the high frequency component of the output signal back to the amplifiers inverting input, thereby preserving phase margin in the overall feedback loop. The values of R1 and C1 should be experimentally determined by the system designer for the desired pulse response. Increased capacitive drive is possible by increasing the value of the capacitor in the feedback loop. DS012051-10 FIGURE 6. LMC6462 Non-Inverting Amplifier, Compensated to Handle a 300 pF Capacitive and 100 kΩ Resistive Load DS012051-8 FIGURE 4. Resistive Isolation of a 300 pF Capacitive Load DS012051-11 FIGURE 7. Pulse Response of LMC6462 Circuit in Figure 6 The pulse response of the circuit shown in Figure 6 is shown in Figure 7. 4.0 Compensating for Input Capacitance It is quite common to use large values of feedback resistance with amplifiers that have ultra-low input current, like the LMC6462/4. Large feedback resistors can react with small values of input capacitance due to transducers, photodiodes, and circuits board parasitics to reduce phase margins. DS012051-9 FIGURE 5. Pulse Response of the LMC6462 Circuit Shown in Figure 4 Figure 5 displays the pulse response of the LMC6462/4 circuit in Figure 4. www.national.com 10 Application Information (Continued) DS012051-14 FIGURE 10. Non-Inverting Configuration Offset Voltage Adjustment DS012051-12 FIGURE 8. Canceling the Effect of Input Capacitance The effect of input capacitance can be compensated for by adding a feedback capacitor. The feedback capacitor (as in Figure 8 ), CF, is first estimated by: 6.0 Spice Macromodel A Spice macromodel is available for the LMC6462/4. This model includes a simulation of: or R1 CIN ≤ R2 CF which typically provides significant overcompensation. Printed circuit board stray capacitance may be larger or smaller than that of a breadboard, so the actual optimum value for CF may be different. The values of CF should be checked on the actual circuit. (Refer to the LMC660 quad CMOS amplifier data sheet for a more detailed discussion.) 5.0 Offset Voltage Adjustment Offset voltage adjustment circuits are illustrated in Figure 9 and Figure 10. Large value resistances and potentiometers are used to reduce power consumption while providing typically ± 2.5 mV of adjustment range, referred to the input, for both configurations with VS = ± 5V. • Input common-mode voltage range • Frequency and transient response • GBW dependence on loading conditions • Quiescent and dynamic supply current • Output swing dependence on loading conditions and many more characteristics as listed on the macromodel disk. Contact the National Semiconductor Customer Response Center to obtain an operational amplifier Spice model library disk. 7.0 Printed-Circuit-Board Layout for High-Impedance Work It is generally recognized that any circuit which must operate with less than 1000 pA of leakage current requires special layout of the PC board. When one wishes to take advantage of the ultra-low input current of the LMC6462/4, typically 150 fA, it is essential to have an excellent layout. Fortunately, the techniques of obtaining low leakages are quite simple. First, the user must not ignore the surface leakage of the PC board, even though it may sometimes appear acceptably low, because under conditions of high humidity or dust or contamination, the surface leakage will be appreciable. To minimize the effect of any surface leakage, lay out a ring of foil completely surrounding the LMC6462’s inputs and the terminals of capacitors, diodes, conductors, resistors, relay terminals, etc. connected to the op-amp’s inputs, as in Figure 11. To have a significant effect, guard rings should be placed in both the top and bottom of the PC board. This PC foil must then be connected to a voltage which is at the same voltage as the amplifier inputs, since no leakage current can flow between two points at the same potential. For example, a PC board trace-to-pad resistance of 1012Ω, which is normally considered a very large resistance, could leak 5 pA if the trace were a 5V bus adjacent to the pad of the input. This would cause a 30 times degradation from the LMC6462/4’s actual performance. However, if a guard ring is held within 5 mV of the inputs, then even a resistance of 1011Ω would cause only 0.05 pA of leakage current. See Figure 12 for typical connections of guard rings for standard op-amp configurations. DS012051-13 FIGURE 9. Inverting Configuration Offset Voltage Adjustment 11 www.national.com Application Information (Continued) board at all, but bend it up in the air and use only air as an insulator. Air is an excellent insulator. In this case you may have to forego some of the advantages of PC board construction, but the advantages are sometimes well worth the effort of using point-to-point up-in-the-air wiring. See Figure 13. DS012051-19 (Input pins are lifted out of PC board and soldered directly to components. All other pins connected to PC board.) FIGURE 13. Air Wiring DS012051-15 FIGURE 11. Example of Guard Ring in P.C. Board Layout DS012051-16 Inverting Amplifier DS012051-17 Non-Inverting Amplifier DS012051-18 Follower FIGURE 12. Typical Connections of Guard Rings The designer should be aware that when it is inappropriate to lay out a PC board for the sake of just a few circuits, there is another technique which is even better than a guard ring on a PC board: Don’t insert the amplifier’s input pin into the www.national.com 12 Application Information 8.0 Instrumentation Circuits (Continued) The LMC6464 has the high input impedance, large common-mode range and high CMRR needed for designing instrumentation circuits. Instrumentation circuits designed with the LMC6464 can reject a larger range of common-mode signals than most in-amps. This makes instrumentation circuits designed with the LMC6464 an excellent choice for noisy or industrial environments. Other appli- cations that benefit from these features include analytic medical instruments, magnetic field detectors, gas detectors, and silicon-based transducers. A small valued potentiometer is used in series with Rg to set the differential gain of the three op-amp instrumentation circuit in Figure 14. This combination is used instead of one large valued potentiometer to increase gain trim accuracy and reduce error due to vibration. DS012051-20 FIGURE 14. Low Power Three Op-Amp Instrumentation Amplifier A two op-amp instrumentation amplifier designed for a gain of 100 is shown in Figure 15. Low sensitivity trimming is made for offset voltage, CMRR and gain. Low cost and low power consumption are the main advantages of this two op-amp circuit. Higher frequency and larger common-mode range applications are best facilitated by a three op-amp instrumentation amplifier. DS012051-21 FIGURE 15. Low-Power Two-Op-Amp Instrumentation Amplifier 13 www.national.com Typical Single-Supply Applications TRANSDUCER INTERFACE CIRCUITS DS012051-22 DS012051-25 FIGURE 16. Photo Detector Circuit Photocells can be used in portable light measuring instruments. The LMC6462, which can be operated off a battery, is an excellent choice for this circuit because of its very low input current and offset voltage. LMC6462 AS A COMPARATOR FIGURE 19. Full-Wave Rectifier with Input Current Protection (RI) In Figure 18 Figure 19, RI limits current into the amplifier since excess current can be caused by the input voltage exceeding the supply voltage. PRECISION CURRENT SOURCE DS012051-23 FIGURE 17. Comparator with Hysteresis Figure 17 shows the application of the LMC6462 as a comparator. The hysteresis is determined by the ratio of the two resistors. The LMC6462 can thus be used as a micropower comparator, in applications where the quiescent current is an important parameter. HALF-WAVE AND FULL-WAVE RECTIFIERS DS012051-26 FIGURE 20. Precision Current Source The output current IOUT is given by: OSCILLATORS DS012051-24 FIGURE 18. Half-Wave Rectifier with Input Current Protection (RI) DS012051-27 FIGURE 21. 1 Hz Square-Wave Oscillator For single supply 5V operation, the output of the circuit will swing from 0V to 5V. The voltage divider set up R2, R3 and R4 will cause the non-inverting input of the LMC6462 to move from 1.67V (1⁄3 of 5V) to 3.33V (2⁄3 of 5V). This voltage behaves as the threshold voltage. R1 and C1 determine the time constant of the circuit. The frequency of oscillation, fOSC is www.national.com 14 Typical Single-Supply Applications (Continued) LOW FREQUENCY NULL where ∆t is the time the amplifier input takes to move from 1.67V to 3.33V. The calculations are shown below. where τ = RC = 0.68 seconds → t1 = 0.27 seconds. and → t2 = 0.75 seconds Then, DS012051-28 FIGURE 22. High Gain Amplifier with Low Frequency Null = 1 Hz Output offset voltage is the error introduced in the output voltage due to the inherent input offset voltage VOS, of an amplifier. Output Offset Voltage = (Input Offset Voltage) (Gain) In the above configuration, the resistors R5 and R6 determine the nominal voltage around which the input signal, VIN should be symmetrical. The high frequency component of the input signal VIN will be unaffected while the low frequency component will be nulled since the DC level of the output will be the input offset voltage of the LMC6462 plus the bias voltage. This implies that the output offset voltage due to the top amplifier will be eliminated. 15 www.national.com Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin Small Outline Package Order Number LMC6462AIM or LMC6462BIM NS Package Number M08A 14-Pin Small Outline Package Order Number LMC6464AIM or LMC6464BIM NS Package Number M14A www.national.com 16 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 8-Pin Molded Dual-In-Line Package Order Number LMC6462AIN or LMC6462BIN NS Package Number N08E 14-Pin Molded Dual-In-Line Pacakge Order Number LMC6462AIN or LMC6464BIN NS Package Number N14A 17 www.national.com LMC6462 Dual/LMC6464 Quad Micropower, Rail-to-Rail Input and Output CMOS Operational Amplifier 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 Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com www.national.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 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: sea.support@nsc.com National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 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.