LT1991 Precision, 100µA Gain Selectable Amplifier FEATURES DESCRIPTION n The LT®1991 combines a precision operational amplifier with eight precision resistors to form a one-chip solution for accurately amplifying voltages. Gains from –13 to 14 with a gain accuracy of 0.04% can be achieved using no external components. The device is particularly well suited for use as a difference amplifier, where the excellent resistor matching results in a common mode rejection ratio of greater than 75dB. n n n n n n n n n n n Pin Configurable as a Difference Amplifier, Inverting and Noninverting Amplifier Difference Amplifier Gain Range 1 to 13 CMRR >75dB Noninverting Amplifier Gain Range 0.07 to 14 Inverting Amplifier Gain Range –0.08 to –13 Gain Error <0.04% Gain Drift < 3ppm/°C Wide Supply Range: Single 2.7V to Split ±18V Micropower: 100μA Supply Current Precision: 50μV Maximum Input Offset Voltage 560kHz Gain Bandwidth Product Rail-to-Rail Output Space Saving 10-Lead MSOP and DFN Packages APPLICATIONS n n n n The amplifier features a 50μV maximum input offset voltage and a gain bandwidth product of 560kHz. The device operates from any supply voltage from 2.7V to 36V and draws only 100μA supply current on a 5V supply. The output swings to within 40mV of either supply rail. The resistors have excellent matching, 0.04% over temperature for the 450k resistors. The matching temperature coefficent is guaranteed less than 3ppm/°C. The resistors are extremely linear with voltage, resulting in a gain nonlinearity of less than 10ppm. The LT1991 is fully specified at 5V and ±15V supplies and from –40°C to 125°C. The device is available in space saving 10-lead MSOP and low profile (0.8mm) 3mm × 3mm DFN packages. Handheld Instrumentation Medical Instrumentation Strain Gauge Amplifiers Differential to Single-Ended Conversion L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 5V 50k 450k 150k VM(IN) – ΔVIN VP(IN) INPUT RANGE –0.5V TO 5.1V RIN = 900kΩ + 450k – 450k + 150k Distribution of Resistor Matching VOUT = VREF + ΔVIN SWING 40mV TO EITHER RAIL ROUT <0.1Ω 40 35 PERCENTAGE OF UNITS (%) Rail-to-Rail Gain = 1 Difference Amplifier 4pF LT1991 450k 450k RESISTORS LT1991A 30 25 20 15 10 5 50k 0 –0.04 4pF VREF = 2.5V 1991 TA01 0 –0.02 0.02 RESISTOR MATCHING (%) 0.04 1991 TA01b 1991fg 1 LT1991 ABSOLUTE MAXIMUM RATINGS (Note 1) Total Supply Voltage (V+ to V – ) ................................40V Input Voltage (Pins P1/M1, Note 2) .......................±60V Input Voltage (Other Inputs Note 2) ..................V+ + 0.2V to V – – 0.2V Output Short-Circuit Duration (Note 3) ........... Indefinite Operating Temperature Range (Note 4) LT1991C............................................... –40°C to 85°C LT1991I ................................................ –40°C to 85°C LT1991H ............................................ –40°C to 125°C Specified Temperature Range (Note 5) LT1991C............................................... –40°C to 85°C LT1991I ................................................ –40°C to 85°C LT1991H ............................................ –40°C to 125°C Maximum Junction Temperature DD Package .......................................................... 125°C MS Package ......................................................... 150°C Storage Temperature Range DD Package............................................ –65°C to 125°C MS Package ........................................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) ................. 300°C PIN CONFIGURATION TOP VIEW P1 1 10 M1 P3 2 9 M3 P9 3 8 M9 VEE 4 7 VCC REF 5 6 OUT TOP VIEW P1 P3 P9 VEE REF 1 2 3 4 5 10 9 8 7 6 M1 M3 M9 VCC OUT MS PACKAGE 10-LEAD PLASTIC MSOP DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN EXPOSED PAD CONNECTED TO VEE PCB CONNECTION OPTIONAL TJMAX = 150°C, θJA = 230°C/W TJMAX = 125°C, θJA = 43°C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT1991CDD#PBF LTCT1991CDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C LT1991ACDD#PBF LT1991ACDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C LT1991IDD#PBF LT1991IDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C LT1991AIDD#PBF LT1991AIDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C LT1991HDD#PBF LT1991HDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C LT1991CMS#PBF LT1991CMS#TRPBF LTQD 10-Lead Plastic MSOP –40°C to 85°C LT1991ACMS#PBF LT1991ACMS#TRPBF LTQD 10-Lead Plastic MSOP –40°C to 85°C LT1991IMS#PBF LT1991IMS#TRPBF LTQD 10-Lead Plastic MSOP –40°C to 85°C LT1991AIMS#PBF LT1991AIMS#TRPBF LTQD 10-Lead Plastic MSOP –40°C to 85°C LT1991HMS#PBF LT1991HMS#TRPBF LTQD 10-Lead Plastic MSOP –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 1991fg 2 LT1991 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating temperature range of 0°C to 70°C for C-grade parts and –40°C to 85°C for I-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration, VS = 5V, 0V or ±15V; VCM = VREF = half supply, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN ΔG Gain Error VS = ±15V, VOUT = ±10V; RL = 10k G = 1; LT1991A G = 1; LT1991 G = 3 or 9; LT1991A G = 3 or 9; LT1991 l l l l TYP MAX UNITS ±0.04 ±0.08 ±0.06 ±0.12 % % % % GNL Gain Nonlinearity VS = ±15V; VOUT = ±10V; RL = 10k l 1 10 ppm ΔG/ΔT Gain Drift vs Temperature (Note 6) VS = ±15V; VOUT = ±10V; RL = 10k l 0.3 3 ppm/°C CMRR Common Mode Rejection Ratio, Referred to Inputs (RTI) VS = ±15V; VCM = ±15.2V G = 9; LT1991A G = 3; LT1991A G = 1; LT1991A Any Gain; LT1991 l l l l 80 75 75 60 Input Voltage Range (Note 7) P1/M1 Inputs VS = ±15V; VREF = 0V VS = 5V, 0V; VREF = 2.5V VS = 3V, 0V; VREF = 1.25V l l l –28 –0.5 0.75 27.6 5.1 2.35 V V V P1/M1 Inputs, P9/M9 Connected to REF VS = ±15V; VREF = 0V VS = 5V, 0V; VREF = 2.5V VS = 3V, 0V; VREF = 1.25V l l l –60 –14 –1.5 60 16.8 7.3 V V V P3/M3 Inputs VS = ±15V; VREF = 0V VS = 5V, 0V; VREF = 2.5V VS = 3V, 0V; VREF = 1.25V l l l –15.2 0.5 0.95 15.2 4.2 1.95 V V V P9/M9 Inputs VS = ±15V; VREF = 0V VS = 5V, 0V; VREF = 2.5V VS = 3V, 0V; VREF = 1.25V l l l –15.2 0.85 1.0 15.2 3.9 1.9 V V V 15 50 135 μV μV 15 80 160 μV μV 25 100 200 μV μV 25 150 250 μV μV 0.3 1 2.5 5 7.5 nA nA 50 500 750 pA pA 50 1000 1500 pA pA VCM VOS Op Amp Offset Voltage (Note 8) LT1991AMS, VS = 5V, 0V LT1991AMS, VS = ±15V LT1991MS LT1991DD ΔVOS/ΔT Op Amp Offset Voltage Drift (Note 6) IB Op Amp Input Bias Current (Note 11) IOS Op Amp Input Offset Current (Note 11) l l l l l LT1991A LT1991 en l l l 100 93 90 70 dB dB dB dB μV/°C Op Amp Input Noise Voltage 0.01Hz to 1Hz 0.01Hz to 1Hz 0.1Hz to 10Hz 0.1Hz to 10Hz 0.35 0.07 0.25 0.05 μVP-P μVRMS μVP-P μVRMS Input Noise Voltage Density G = 1; f = 1kHz G = 9; f = 1kHz 180 46 nV/√Hz nV/√Hz 1991fg 3 LT1991 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating temperature range of 0°C to 70°C for C-grade parts and –40°C to 85°C for I-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration, VS = 5V, 0V or ±15V; VCM = VREF = half supply, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS RIN Input Impedance (Note 10) P1 (M1 = Ground) P3 (M3 = Ground) P9 (M9 = Ground) l l l 630 420 350 900 600 500 1170 780 650 kΩ kΩ kΩ M1 (P1 = Ground) M3 (P3 = Ground) M9 (P9 = Ground) l l l 315 105 35 450 150 50 585 195 65 kΩ kΩ kΩ 450k Resistors, LT1991A Other Resistors, LT1991A 450k Resistors, LT1991 Other Resistors, LT1991 l l l l 0.01 0.02 0.02 0.04 0.04 0.06 0.08 0.12 % % % % 0.3 –30 3 ΔR Resistor Matching (Note 9) ΔR/ΔT Resistor Temperature Coefficient (Note 6) Resistor Matching Absolute Value l l PSRR Power Supply Rejection Ratio l VS = ±1.35V to ±18V (Note 8) l Minimum Supply Voltage 135 dB 2.4 2.7 V 40 55 65 110 mV mV mV 150 225 275 300 mV mV mV No Load VS = 5V, 0V VS = 5V, 0V VS = ±15V l l 1mA Load VS = 5V, 0V VS = 5V, 0V VS = ±15V l l Output Short-Circuit Current (Sourcing) Drive Output Positive; Short Output to Ground l 8 4 12 mA mA Output Short-Circuit Current (Sinking) Drive Output Negative; Short Output to VS or Midsupply l 8 4 21 mA mA BW –3dB Bandwidth G=1 G=3 G=9 110 78 40 kHz kHz kHz GBWP Op Amp Gain Bandwidth Product f = 10kHz 560 kHz tr, tf Rise Time, Fall Time G = 1; 0.1V Step; 10% to 90% G = 9; 0.1V Step; 10% to 90% 3 8 μs μs ts Settling Time to 0.01% G = 1; VS = 5V, 0V; 2V Step G = 1; VS = 5V, 0V; –2V Step G = 1; VS = ±15V, 10V Step G = 1; VS = ±15V, –10V Step 42 48 114 74 μs μs μs μs SR Slew Rate VS = 5V, 0V; VOUT = 1V to 4V VS = ±15V; VOUT = ±10V; VMEAS = ±5V 0.12 0.12 V/μs V/μs Is Supply Current VS = 5V, 0V VOUT ISC Output Voltage Swing (to Either Rail) 105 ppm/°C ppm/°C VS = ±15V l l l l 0.06 0.08 100 110 150 μA μA 130 160 210 μA μA 1991fg 4 LT1991 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating temperature range of –40°C to 125°C for H-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration, VS = 5V, 0V or ±15V; VCM = VREF = half supply, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN ΔG Gain Error VS = ±15V, VOUT = ±10V; RL = 10k G=1 G = 3 or 9 l l TYP MAX UNITS ±0.08 ±0.12 % % GNL Gain Nonlinearity VS = ±15V; VOUT = ±10V; RL = 10k l 1 10 ppm ΔG/ΔT Gain Drift vs Temperature (Note 6) VS = ±15V; VOUT = ±10V; RL = 10k l 0.3 3 ppm/°C CMRR Common Mode Rejection Ratio, Referred to Inputs (RTI) VS = ±15V; VCM = ±15.2V G=9 G=3 G=1 l l l 77 70 70 Input Voltage Range (Note 7) P1/M1 Inputs VS = ±15V; VREF = 0V VS = 5V, 0V; VREF = 2.5V VS = 3V, 0V; VREF = 1.25V l l l –28 –0.5 0.75 27.6 5.1 2.35 V V V P1/M1 Inputs, P9/M9 Connected to REF VS = ±15V; VREF = 0V VS = 5V, 0V; VREF = 2.5V VS = 3V, 0V; VREF = 1.25V l l l –60 –14 –1.5 60 16.8 7.3 V V V P3/M3 Inputs VS = ±15V; VREF = 0V VS = 5V, 0V; VREF = 2.5V VS = 3V, 0V; VREF = 1.25V l l l –15.2 0.5 0.95 15.2 4.2 1.95 V V V P9/M9 Inputs VS = ±15V; VREF = 0V VS = 5V, 0V; VREF = 2.5V VS = 3V, 0V; VREF = 1.25V l l l –15.2 0.85 1.0 15.2 3.9 1.9 V V V 25 100 285 μV μV 25 150 295 μV μV 0.3 1 μV/°C 2.5 5 25 nA nA 50 1000 4500 pA pA VCM VOS Op Amp Offset Voltage (Note 8) LT1991MS LT1991DD ΔVOS/ΔT Op Amp Offset Voltage Drift (Note 6) IB Op Amp Input Bias Current (Note 11) IOS Op Amp Input Offset Current (Note 11) l l l l l 100 93 90 dB dB dB Op Amp Input Noise Voltage 0.01Hz to 1Hz 0.01Hz to 1Hz 0.1Hz to 10Hz 0.1Hz to 10Hz 0.35 0.07 0.25 0.05 μVP-P μVRMS μVP-P μVRMS en Input Noise Voltage Density G = 1; f = 1kHz G = 9; f = 1kHz 180 46 nV/√Hz nV/√Hz RIN Input Impedance (Note 10) P1 (M1 = Ground) P3 (M3 = Ground) P9 (M9 = Ground) l l l 630 420 350 900 600 500 1170 780 650 kΩ kΩ kΩ M1 (P1 = Ground) M3 (P3 = Ground) M9 (P9 = Ground) l l l 315 105 35 450 150 50 585 195 65 kΩ kΩ kΩ 450k Resistors Other Resistors l l 0.02 0.04 0.08 0.12 % % l l 0.3 –30 3 ΔR Resistor Matching (Note 9) ΔR/ΔT Resistor Temperature Coefficient (Note 6) Resistor Matching Absolute Value ppm/°C ppm/°C 1991fg 5 LT1991 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating temperature range of –40°C to 125°C for H-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration, VS = 5V, 0V or ±15V; VCM = VREF = half supply, unless otherwise noted. SYMBOL PARAMETER CONDITIONS PSRR Power Supply Rejection Ratio VS = ±1.35V to ±18V (Note 8) TYP 105 135 l Minimum Supply Voltage MAX UNITS dB 2.4 2.7 V 40 55 75 120 mV mV mV 150 225 300 340 mV mV mV No Load VS = 5V, 0V VS = 5V, 0V VS = ±15V l l 1mA Load VS = 5V, 0V VS = 5V, 0V VS = ±15V l l Output Short-Circuit Current (Sourcing) Drive Output Positive; Short Output to Ground l 8 4 12 mA mA Output Short-Circuit Current (Sinking) Drive Output Negative; Short Output to VS or Midsupply l 8 4 21 mA mA BW –3dB Bandwidth G=1 G=3 G=9 110 78 40 kHz kHz kHz GBWP Op Amp Gain Bandwidth Product f = 10kHz 560 kHz tr, tf Rise Time, Fall Time G = 1; 0.1V Step; 10% to 90% G = 9; 0.1V Step; 10% to 90% 3 8 μs μs ts Settling Time to 0.01% G = 1; VS = 5V, 0V; 2V Step G = 1; VS = 5V, 0V; –2V Step G = 1; VS = ±15V, 10V Step G = 1; VS = ±15V, –10V Step 42 48 114 74 μs μs μs μs SR Slew Rate VS = 5V, 0V; VOUT = 1V to 4V VS = ±15V; VOUT = ±10V; VMEAS = ±5V 0.12 0.12 V/μs V/μs Is Supply Current VS = 5V, 0V VOUT ISC Output Voltage Swing (to Either Rail) l MIN VS = ±15V Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The P3/M3 and P9/M9 inputs should not be taken more than 0.2V beyond the supply rails. The P1/M1 inputs can withstand ±60V if P9/M9 are grounded and VS = ±15V (see Applications Information section about “High Voltage CM Difference Amplifiers”). l l 0.06 0.08 l l 100 110 180 μA μA 130 160 250 μA μA Note 6: This parameter is not 100% tested. Note 7: Input voltage range is guaranteed by the CMRR test at VS = ±15V. For the other voltages, this parameter is guaranteed by design and through correlation with the ±15V test. See the Applications Information section to determine the valid input voltage range under various operating conditions. Note 3: A heat sink may be required to keep the junction temperature below absolute maximum ratings. Note 8: Offset voltage, offset voltage drift and PSRR are defined as referred to the internal op amp. You can calculate output offset as follows. In the case of balanced source resistance, VOS,OUT = VOS • NOISEGAIN + IOS • 450k + IB • 450k • (1– RP/RN) where RP and RN are the total resistance at the op amp positive and negative terminal respectively. Note 4: Both the LT1991C and LT1991I are guaranteed functional over the –40°C to 85°C temperature range. The LTC1991H is guaranteed functional over the –40°C to 125°C temperature range. Note 9: Applies to resistors that are connected to the inverting inputs. Resistor matching is not tested directly, but is guaranteed by the gain error test. Note 5: The LT1991C is guaranteed to meet the specified performance from 0°C to 70°C and is designed, characterized and expected to meet specified performance from –40°C to 85°C but is not tested or QA sampled at these temperatures. The LT1991I is guaranteed to meet specified performance from –40°C to 85°C. The LT1991H is guaranteed to meet specified performance from –40°C to 125°C. Note 10: Input impedance is tested by a combination of direct measurements and correlation to the CMRR and gain error tests. Note 11: IB and IOS are tested at VS = 5V, 0V only. 1991fg 6 LT1991 TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage Swing vs Temperature 200 Output Voltage Swing vs Load Current (Output Low) VCC VS = 5V, 0V NO LOAD OUTPUT VOLTAGE SWING (mV) 175 TA = 85°C 150 TA = 25°C 125 TA = –40°C 100 75 50 60 VEE –50 0 4 6 8 10 12 14 16 18 20 SUPPLY VOLTAGE (±V) –25 0 25 50 75 100 TA = 25°C –500 –600 –700 –800 –900 –1000 0 1 2 3 4 5 6 7 LOAD CURRENT (mA) 8 9 15 10 5 3 4 5 1 125 6 7 8 9 10 11 12 13 GAIN (V/V) 1991 G07 –0.04 2 3 4 5 1991 G05 6 7 8 9 10 11 12 13 GAIN (V/V) 1991 G06 Slew Rate vs Temperature 0.30 0.25 –0.01 –0.03 2 100 0 –750 1 –50 –150 50 25 0 75 TEMPERATURE (°C) –25 0.01 –0.02 VS = 5V, 0V REPRESENTATIVE PARTS 0 GAIN = 1 VS = ±15V VOUT = ±10V TA = 25°C 0.03 –500 10 50 SLEW RATE (V/μs) –250 9 –100 0.02 0 8 100 Gain Error vs Load Current GAIN ERROR (%) OUTPUT OFFSET VOLTAGE (µV) SOURCING 0.04 500 –1000 150 20 1991 G04 250 3 4 5 6 7 LOAD CURRENT (mA) 2 1 Input Offset Voltage vs Difference Gain VS = 5V, 0V 0 –50 10 VS = 5V, 0V REPRESENTATIVE PARTS 750 0 1991 G03 SINKING Output Offset Voltage vs Difference Gain 1000 VEE 125 INPUT OFFSET VOLTAGE (μV) OUTPUT SHORT-CIRCUIT CURRENT (mA) OUTPUT VOLTAGE SWING (mV) TA = 85°C –400 TA = –40°C 400 1991 G02 25 TA = –40°C –300 TA = 25°C 600 Output Short-Circuit Current vs Temperature –100 –200 800 TEMPERATURE (°C) Output Voltage Swing vs Load Current (Output High) VS = 5V, 0V TA = 85°C 1000 200 1991 G01 VCC VS = 5V, 0V 1200 OUTPUT LOW (LEFT AXIS) 20 2 –40 –60 25 0 –20 OUTPUT HIGH (RIGHT AXIS) 40 1400 OUTPUT VOLTAGE (mV) Supply Current vs Supply Voltage SUPPLY CURRENT (μA) (Difference Amplifier Configuration) GAIN = 1 VS = ±15V VOUT = ±10V 0.20 SR– (FALLING EDGE) 0.15 SR+ (RISING EDGE) 0.10 0.05 REPRESENTATIVE UNITS 0 1 2 3 LOAD CURRENT (mA) 4 5 1991 G08 0 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 1991 G09 1991fg 7 LT1991 TYPICAL PERFORMANCE CHARACTERISTICS Bandwidth vs Gain CMRR vs Frequency 120 VS = 5V, 0V TA = 25°C 110 VS = 5V, 0V TA = 25°C GAIN = 9 100 GAIN = 1 90 90 GAIN = 3 CMRR (dB) 60 40 20 70 60 50 1 2 3 4 30 20 20 10 10 100 1k 10k FREQUENCY (Hz) VS = 5V, 0V TA = 25°C GAIN = 1 VS = ±15V GAIN ERROR (%) CMRR (dB) GAIN = 1 60 40 0.1 0 –50 –25 0.01 10 100 1k FREQUENCY (Hz) 10k 100k REPRESENTATIVE UNITS 50 25 75 0 TEMPERATURE (°C) 100 1991 G13 20 Gain and Phase vs Frequency 2 VS = 5V, 0V TA = 25°C VS = 5V, 0V TA = 25°C 0 GAIN = 1 1 PHASE GAIN = 9 0 GAIN (dB) GAIN (dB) GAIN = 3 GAIN = 1 –10 GAIN –45 –2 –90 –3 –4 –135 –6 –180 –7 1 10 100 FREQUENCY (kHz) 600 1991 G16 REPRESENTATIVE UNITS 50 25 75 0 TEMPERATURE (°C) 100 –8 0.5 1 10 FREQUENCY (kHz) 100 125 0.01Hz to 1Hz Voltage Noise –5 –20 0.010 1991 G15 PHASE (deg) 0 0.015 0 –50 –25 125 –1 10 0.020 1991 G14 Gain vs Frequency 30 GAIN = 1 VS = ±15V 0.005 20 1 100k 0.025 80 GAIN = 3 1 1k 10k FREQUENCY (Hz) Gain Error vs Temperature 0.030 100 100 GAIN = 9 100 1991 G12 CMRR vs Temperature 120 10 10 1991 G11 Output Impedance vs Frequency OUTPUT IMPEDANCE (Ω) 0 1M 100k 1991 G10 1000 50 40 10 GAIN = 3 60 30 5 6 7 8 9 10 11 12 13 GAIN SETTING (V/V) GAIN = 1 70 40 0 GAIN = 9 80 PSRR (dB) 80 80 VS = 5V, 0V TA = 25°C 110 100 100 –3dB BANDWIDTH (kHz) PSRR vs Frequency 120 400 VS = ±15V TA = 25°C MEASURED IN G =13 REFERRED TO OP AMP INPUTS OP AMP VOLTAGE NOISE (100nV/DIV) 120 0 (Difference Amplifier Configuration) 0 10 20 30 40 50 60 70 80 90 100 TIME (s) 1991 G17 1991 G21 1991fg 8 LT1991 TYPICAL PERFORMANCE CHARACTERISTICS Small Signal Transient Response Small Signal Transient Response Small Signal Transient Response GAIN = 9 GAIN = 3 GAIN = 1 50mV/DIV 50mV/DIV 50mV/DIV 1991 G18 5μs/DIV PIN FUNCTIONS 1991 G19 5μs/DIV 5μs/DIV 1991 G20 (Difference Amplifier Configuration) P1 (Pin 1): Noninverting Gain-of-1 input. Connects a 450k internal resistor to the op amp’s noninverting input. OUT (Pin 6): Output. VOUT = VREF + 1 • (VP1 – VM1) + 3 • (VP3 – VM3) + 9 • (VP9 – VM9). P3 (Pin 2): Noninverting Gain-of-3 input. Connects a 150k internal resistor to the op amp’s noninverting input. VCC (Pin 7): Positive Power Supply. Can be anything from 2.7V to 36V above the VEE voltage. P9 (Pin 3): Noninverting Gain-of-9 input. Connects a 50k internal resistor to the op amp’s noninverting input. M9 (Pin 8): Inverting Gain-of-9 input. Connects a 50k internal resistor to the op amp’s inverting input. VEE (Pin 4): Negative Power Supply. Can be either ground (in single supply applications), or a negative voltage (in split supply applications). M3 (Pin 9): Inverting Gain-of-3 input. Connects a 150k internal resistor to the op amp’s inverting input. REF (Pin 5): Reference Input. Sets the output level when difference between inputs is zero. Connects a 450k internal resistor to the op amp’s noninverting input. M1 (Pin 10): Inverting Gain-of-1 input. Connects a 450k internal resistor to the op amp’s inverting input. Exposed Pad: Must be soldered to PCB. BLOCK DIAGRAM M1 M3 M9 VCC 10 9 8 7 OUT 6 50k 450k 150k 4pF 450k INM OUT 450k INP LT1991 150k 450k 50k 4pF 1 2 3 4 5 P1 P3 P9 VEE REF 1991 BD 1991fg 9 LT1991 APPLICATIONS INFORMATION Introduction The LT1991 may be the last op amp you ever have to stock. Because it provides you with several precision matched resistors, you can easily configure it into several different classical gain circuits without adding external components. The several pages of simple circuits in this data sheet demonstrate just how easy the LT1991 is to use. It can be configured into difference amplifiers, as well as into inverting and noninverting single ended amplifiers. The fact that the resistors and op amp are provided together in such a small package will often save you board space and reduce complexity for easy probing. The Op Amp The op amp internal to the LT1991 is a precision device with 15μV typical offset voltage and 3nA input bias current. The input offset current is extremely low, so matching the source resistance seen by the op amp inputs will provide for the best output accuracy. The op amp inputs are not rail-to-rail, but extend to within 1.2V of VCC and 1V of VEE. For many configurations though, the chip inputs will function rail-to-rail because of effective attenuation to the +input. The output is truly rail-to-rail, getting to within 40mV of the supply rails. The gain bandwidth product of the op amp is about 560kHz. In noise gains of 2 or more, it is stable into capacitive loads up to 500pF. In noise gains below 2, it is stable into capacitive loads up to 100pF. The Resistors The resistors internal to the LT1991 are very well matched SiChrome based elements protected with barrier metal. Although their absolute tolerance is fairly poor (±30%), their matching is to within 0.04%. This allows the chip to achieve a CMRR of 75dB, and gain errors within 0.04%. The resistor values are 50k, 150k, and 2 of 450k, connected to each of the inputs. The resistors have power limitations of 1watt for the 450k resistors, 0.3watt for the 150k resistors and 0.5watt for the 50k resistors; however, in practice, power dissipation will be limited well below these values by the maximum voltage allowed on the input and REF pins. The 450k resistors connected to the M1 and P1 inputs are isolated from the substrate, and can therefore be taken beyond the supply voltages. The naming of the pins “P1,” “P3,” “P9,” etc., is based on their relative admittances. Because it has 9 times the admittance, the voltage applied to the P9 input has 9 times the effect of the voltage applied to the P1 input. Bandwidth The bandwidth of the LT1991 will depend on the gain you select (or more accurately the noise gain resulting from the gain you select). In the lowest configurable gain of 1, the –3dB bandwidth is limited to 450kHz, with peaking of about 2dB at 280kHz. In the highest configurable gains, bandwidth is limited to 32kHz. Input Noise The LT1991 input noise is dominated by the Johnson noise of the internal resistors (√4kTR). Paralleling all four resistors to the +input gives a 32.1kΩ resistance, for 23nV/√Hz of voltage noise. The equivalent network on the –input gives another 23nV/√Hz , and taking their RMS sum gives a total 33nV/√Hz input referred noise floor. Output noise depends on configuration and noise gain. Input Resistance The LT1991 input resistances vary with configuration, but once configured are apparent on inspection. Note that resistors connected to the op amp’s –input are looking into a virtual ground, so they simply parallel. Any feedback resistance around the op amp does not contribute to input resistance. Resistors connected to the op amp’s +input are looking into a high impedance, so they add as parallel or series depending on how they are connected, and whether or not some of them are grounded. The op amp +input itself presents a very high GΩ impedance. In the classical noninverting op amp configuration, the LT1991 presents the high input impedance of the op amp, as is usual for the noninverting case. Common Mode Input Voltage Range The LT1991 valid common mode input range is limited by three factors: 1. Maximum allowed voltage on the pins 2. The input voltage range of the internal op amp 3. Valid output voltage 1991fg 10 LT1991 APPLICATIONS INFORMATION The maximum voltage allowed on the P3, M3, P9, and M9 inputs includes the positive and negative supply plus a diode drop. These pins should not be driven more than 0.2V outside of the supply rails. This is because they are connected through diodes to internal manufacturing postpackage trim circuitry, and through a substrate diode to VEE. If more than 10mA is allowed to flow through these pins, there is a risk that the LT1991 will be detrimmed or damaged. The P1 and M1 inputs do not have clamp diodes or substrate diodes or trim circuitry and can be taken well outside the supply rails. The maximum allowed voltage on the P1 and M1 pins is ±60V. The input voltage range of the internal op amp extends to within 1.2V of VCC and 1V of VEE. The voltage at which the op amp inputs common mode is determined by the voltage at the op amp’s +input, and this is determined by the voltages on pins P1, P3, P9 and REF (see “Calculating Input Voltage Range” section). This is true provided that the op amp is functioning and feedback is maintaining the inputs at the same voltage, which brings us to the third requirement. For valid circuit function, the op amp output must not be clipped. The output will clip if the input signals are attempting to force it to within 40mV of its supply voltages. This usually happens due to too large a signal level, but it can also occur with zero input differential and must therefore be included as an example of a common mode problem. Consider Figure 1. This shows the LT1991 configured as a gain of 13 difference amplifier on a single supply with the output REF connected to ground. This is a great circuit, but it does not support VDM = 0V at any common mode because the output clips into ground while trying to produce 0VOUT. It can be fixed simply by declaring the valid input differential range not to extend below +4mV, or by elevating the REF pin above 40mV, or by providing a negative supply. Calculating Input Voltage Range Figure 2 shows the LT1991 in the generalized case of a difference amplifier, with the inputs shorted for the common mode calculation. The values of RF and RG are dictated by how the P inputs and REF pin are connected. By superposition we can write: VINT = VEXT • (RF/(RF + RG)) + VREF • (RG/(RF + RG)) Or, solving for VEXT : VEXT = VINT • (1 + RG/RF) – VREF • RG/RF But valid VINT voltages are limited to VCC – 1.2V and VEE + 1V, so: MAX VEXT = (VCC – 1.2) • (1 + RG/RF) – VREF • RG/RF and: MIN VEXT = (VEE + 1) • (1 + RG/RF) – VREF • RG/RF RF 5V 8 50k 9 150k 10 450k – VCM 2.5V 1 450k 2 150k 3 50k – 450k VEXT 4pF VDM 0V+ VCC RG 7 VINT RG + VEE VREF RF – 6 VOUT = 13 • VDM + 1991 F02 Figure 2. Calculating CM Input Voltage Range 4pF 450k REF 5 LT1991 4 1991 F01 Figure 1. Difference Amplifier Cannot Produce 0V on a Single Supply. Provide a Negative Supply, or Raise Pin 5, or Provide 4mV of VDM These two voltages represent the high and low extremes of the common mode input range, if the other limits have not already been exceeded (1 and 3, above). In most cases, the inverting inputs M1 through M9 can be taken further than these two extremes because doing this does not move the op amp input common mode. To calculate the limit on this additional range, see Figure 3. Note that, 1991fg 11 LT1991 APPLICATIONS INFORMATION with VMORE = 0, the op amp output is at VREF. From the max VEXT (the high cm limit), as VMORE goes positive, the op amp output will go more negative from VREF by the amount VMORE • RF/RG, so: VOUT = VREF – VMORE • RF/RG Or: VMORE = (VREF – VOUT) • RG/RF The most negative that VOUT can go is VEE + 0.04V, so: Max VMORE = (VREF – VEE – 0.04V) • RG/RF (should be positive) The situation where this function is negative, and therefore problematic, when VREF = 0 and VEE = 0, has already been dealt with in Figure 1. The strength of the equation is demonstrated in that it provides the three solutions suggested in Figure 1: raise VREF , lower VEE, or provide some negative VMORE. representation of the circuit on the top. The LT1991 is shown on the bottom configured in a precision gain of 5.5. One of the benefits of the noninverting op amp configuration is that the input impedance is extremely high. The LT1991 maintains this benefit. Given the finite number of available feedback resistors in the LT1991, the number of gain configurations is also finite. The complete list of such Hi-Z input noninverting gain configurations is shown in Table 1. Many of these are also represented in Figure 5 in schematic form. Note that the P-side resistor inputs have been connected so as to match the source impedance seen by the internal op amp inputs. Note also that gain and noise gain are identical, for optimal precision. RF RG – VOUT VIN Likewise, from the lower common mode extreme, making the negative input more negative will raise the output voltage, limited by VCC – 0.04V. + VOUT = GAIN • VIN GAIN = 1 + RF/RG CLASSICAL NONINVERTING OP AMP CONFIGURATION. YOU PROVIDE THE RESISTORS. MIN VMORE = (VREF – VCC + 0.04V) • RG/RF (should be negative) RF 8 50k 9 150k 10 450k 1 450k 2 150k 3 50k 450k 4pF VCC RG – VMORE VEXT MAX OR MIN VINT RG + VEE VREF RF 1991 F03 Figure 3. Calculating Additional Voltage Range of Inverting Inputs – 6 VOUT + 4pF 450k LT1991 Again, the additional input range calculated here is only available provided the other remaining constraint is not violated, the maximum voltage allowed on the pin. The Classical Noninverting Amplifier: High Input Z Perhaps the most common op amp configuration is the noninverting amplifier. Figure 4 shows the textbook 5 VIN CLASSICAL NONINVERTING OP AMP CONFIGURATION IMPLEMENTED WITH LT1991. RF = 225k, RG = 50k, GAIN = 5.5. GAIN IS ACHIEVED BY GROUNDING, FLOATING OR FEEDING BACK THE AVAILABLE RESISTORS TO ARRIVE AT DESIRED RF AND RG. WE PROVIDE YOU WITH <0.1% RESISTORS. 1991 F04 Figure 4. The LT1991 as a Classical Noninverting Op Amp 1991fg 12 LT1991 APPLICATIONS INFORMATION Table 1. Configuring the M Pins for Simple Noninverting Gains. The P Inputs are driven as shown in the examples on the next page. M9, M3, M1 Connection Gain M9 M3 M1 1 Output Output Output 1.077 Output Output Ground 1.1 Output Float Ground 1.25 Float Output Ground 1.273 Output Ground Output 1.3 Output Ground Float 1.4 Output Ground Ground 2 Float Float Ground 2.5 Float Ground Output 2.8 Ground Output Output 3.25 Ground Output Float 3.5 Ground Output Ground 4 Float Ground Float 5 Float Ground Ground 5.5 Ground Float Output 7 Ground Ground Output 10 Ground Float Float 11 Ground Float Ground 13 Ground Ground Float 14 Ground Ground Ground 1991fg 13 LT1991 APPLICATIONS INFORMATION VS+ 8 M9 9 M3 10 M1 VIN 1 P1 2 P3 3 P9 VS+ 8 M9 9 M3 10 M1 7 VCC LT1991 VEE OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 VIN 4 VS– 7 VCC LT1991 VEE 6 VOUT VIN 4 LT1991 VEE OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 VS– VS+ 7 VCC LT1991 VEE OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 VS+ 7 VCC VEE 7 VCC LT1991 VEE VOUT 1 P1 2 P3 3 P9 VIN 4 OUT REF 5 6 VOUT 4 VS– GAIN = 5.5 VS+ 8 M9 9 M3 10 M1 6 VOUT 4 8 M9 9 M3 10 M1 GAIN = 5 OUT REF 5 6 VIN GAIN = 4 VIN VEE OUT REF 5 GAIN = 3.25 VIN LT1991 LT1991 VS– VS– VIN 1 P1 2 P3 3 P9 7 VCC VS+ 8 M9 9 M3 10 M1 7 VCC 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 GAIN = 2 VS+ 1 P1 2 P3 3 P9 OUT REF 5 VS– GAIN = 1 8 M9 9 M3 10 M1 VS+ 8 M9 9 M3 10 M1 VS– VS+ 8 M9 9 M3 10 M1 7 VCC LT1991 VEE OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 VS– 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4 VS– VIN GAIN = 7 GAIN = 10 GAIN = 11 VS+ 8 M9 9 M3 10 M1 VIN 1 P1 2 P3 3 P9 VS+ 8 M9 9 M3 10 M1 7 VCC LT1991 VEE OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 VS– 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4 VS– VIN GAIN = 13 GAIN = 14 1991 F05 Figure 5. Some Implementations of Classical Noninverting Gains Using the LT1991. High Input Z Is Maintained. 1991fg 14 LT1991 APPLICATIONS INFORMATION Attenuation Using the P Input Resistors Attenuation happens as a matter of fact in difference amplifier configurations, but it is also used for reducing peak signal level or improving input common mode range even in single ended systems. When signal conditioning indicates a need for attenuation, the LT1991 resistors are ready at hand. The four precision resistors can provide several attenuation levels, and these are tabulated in Table 2 as a design reference. VIN VIN OKAY UP TO ±60V RA VINT RG VINT = A • VIN A = RG/(RA + RG) 1 450k 2 150k 3 50k VINT + 4pF 450k LT1991 5 CLASSICAL ATTENUATOR LT1991 ATTENUATING TO THE +INPUT BY DRIVING AND GROUNDING AND FLOATING INPUTS RA = 450k, RG = 50k, SO A = 0.1. 1991 F06 Figure 6. LT1991 Provides for Easy Attenuation to the Op Amp’s +Input. The P1 Input Can Be Taken Well Outside of the Supplies. Because the attenuations and the noninverting gains are set independently, they can be combined. This provides high gain resolution, about 340 unique gains between 0.077 and 14, as plotted in Figure 7. This is too large a number to tabulate, but the designer can calculate achievable gain by taking the vector product of the gains and attenuations in Tables 1 and 2, and seeking the best match. Average gain resolution is 1.5%, with a worst-case of 7%. 100 GAIN 10 Table 2. Configuring the P Pins for Various Attenuations. Those Shown in Bold Are Functional Even When the Input Drive Exceeds the Supplies. P9, P3, P1, REF Connection A P9 P3 P1 REF 0.0714 Ground Ground Drive Ground 0.0769 Ground Ground Drive Float 0.0909 Ground Float Drive Ground 0.1 Ground Float Drive Float 0.143 Ground Ground Drive Drive 0.182 Ground Float Drive Drive 0.2 Float Ground Drive Ground 0.214 Ground Drive Ground Ground 0.231 Ground Drive Float Ground 0.25 Float Ground Drive Float 0.286 Ground Drive Drive Ground 0.308 Ground Drive Drive Float 0.357 Ground Drive Drive Drive 0.4 Float Ground Drive Drive 0.5 Float Float Drive Ground 0.6 Float Drive Ground Ground 0.643 Drive Ground Ground Ground 0.692 Drive Ground Float Ground 0.714 Drive Ground Drive Ground 0.75 Float Drive Float Ground 0.769 Drive Ground Drive Float 0.786 Drive Ground Drive Drive 0.8 Float Drive Drive Ground 0.818 Drive Float Ground Ground 0.857 Drive Drive Ground Ground 0.9 Drive Float Float Ground 0.909 Drive Float Drive Ground 0.923 Drive Drive Float Ground 0.929 Drive Drive Drive Ground 1 Drive Drive Drive Drive 1 0.1 0.01 0 50 100 150 200 COUNT 250 300 350 1991 F07 Figure 7. Over 346 Unique Gain Settings Achievable with the LT1991 by Combining Attenuation with Noninverting Gain 1991fg 15 LT1991 APPLICATIONS INFORMATION Inverting Configuration Table 3. Configuring the M Pins for Simple Inverting Gains The inverting amplifier, shown in Figure 8, is another classical op amp configuration. The circuit is actually identical to the noninverting amplifier of Figure 4, except that VIN and GND have been swapped. The list of available gains is shown in Table 3, and some of the circuits are shown in Figure 9. Noise gain is 1+|Gain|, as is the usual case for inverting amplifiers. Again, for the best DC performance, match the source impedance seen by the op amp inputs. RF RG VIN – VOUT + VOUT = GAIN • VIN GAIN = – RF/RG CLASSICAL INVERTING OP AMP CONFIGURATION. YOU PROVIDE THE RESISTORS. VIN (DRIVE) 8 50k 9 150k 10 450k 1 450k 2 150k 3 50k 450k M9, M3, M1 Connection Gain M9 M3 M1 –0.077 Output Output Drive –0.1 Output Float Drive –0.25 Float Output Drive –0.273 Output Drive Output –0.3 Output Drive Float –0.4 Output Drive Drive –1 Float Float Drive –1.5 Float Drive Output –1.8 Drive Output Output –2.25 Drive Output Float –2.5 Drive Output Drive –3 Float Drive Float –4 Float Drive Drive –4.5 Drive Float Output –6 Drive Drive Output –9 Drive Float Float –10 Drive Float Drive –12 Drive Drive Float –13 Drive Drive Drive 4pF – 6 VOUT + 4pF 450k LT1991 5 CLASSICAL INVERTING OP AMP CONFIGURATION IMPLEMENTED WITH LT1991. RF = 225k, RG = 50k, GAIN = –4.5. GAIN IS ACHIEVED BY GROUNDING, FLOATING OR FEEDING BACK THE AVAILABLE RESISTORS TO ARRIVE AT DESIRED RF AND RG. WE PROVIDE YOU WITH <0.1% RESISTORS. 1991 F08 Figure 8. The LT1991 as a Classical Inverting Op Amp. Note the Circuit Is Identical to the Noninverting Amplifier, Except that VIN and Ground Have Been Swapped. 1991fg 16 LT1991 APPLICATIONS INFORMATION VS+ 8 M9 9 M3 10 M1 VIN 1 P1 2 P3 3 P9 VS+ 7 VCC LT1991 VEE OUT REF 5 6 8 M9 9 M3 10 M1 VIN VOUT 1 P1 2 P3 3 P9 4 VS– LT1991 VEE 1 P1 2 P3 3 P9 LT1991 VEE OUT REF 5 6 VIN VOUT 1 P1 2 P3 3 P9 4 VEE LT1991 VEE OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 VIN OUT REF 5 6 VOUT 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE VS– VS+ VIN LT1991 OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 1 P1 2 P3 3 P9 VEE OUT REF 5 4 LT1991 VEE OUT REF 5 6 VOUT 4 GAIN = –10 VS+ 7 VCC LT1991 7 VCC VS– VS+ VIN VOUT 4 8 M9 9 M3 10 M1 GAIN = –9 8 M9 9 M3 10 M1 6 GAIN = –4.5 VS– GAIN = –6 OUT REF 5 VS– 7 VCC VEE VOUT 4 VS+ VIN 6 VS+ 4 8 M9 9 M3 10 M1 OUT REF 5 GAIN = –2.25 GAIN = –4 7 VCC LT1991 LT1991 VS– 7 VCC VS+ VEE 1 P1 2 P3 3 P9 VS– GAIN = –3 1 P1 2 P3 3 P9 VOUT 7 VCC VS+ 8 M9 9 M3 10 M1 VS– VIN 6 GAIN = –1 7 VCC 8 M9 9 M3 10 M1 OUT REF 5 4 VS+ VIN VIN 7 VCC VS– GAIN = –0.25 8 M9 9 M3 10 M1 VS+ 8 M9 9 M3 10 M1 6 VIN VOUT 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4 VS– VS– GAIN = –12 GAIN = –13 1991 F09 Figure 9. It Is Simple to Get Precision Inverting Gains with the LT1991. Input Impedance Varies from 45kΩ (Gain = –13) to 450kΩ (Gain = –1). 1991fg 17 LT1991 APPLICATIONS INFORMATION Difference Amplifiers RF The resistors in the LT1991 allow it to easily make difference amplifiers also. Figure 10 shows the basic 4-resistor difference amplifier and the LT1991. A difference gain of 3 is shown, but notice the effect of the additional dashed connections. By connecting the 450k resistors in parallel, the gain is reduced by a factor of 2. Of course, with so many resistors, there are many possible gains. Table 4 shows the difference gains and how they are achieved. Note that, as for inverting amplifiers, the noise gain is 1 more than the signal gain. VIN– VIN+ RG RG – VOUT + RF CLASSICAL DIFFERENCE AMPLIFIER USING THE LT1991 8 M9 50k Table 4. Connections Giving Difference Gains for the LT1991 Gain VIN+ VIN– Output GND (REF) 0.077 P1 M1 M3, M9 P3, P9 0.1 P1 M1 M9 P9 0.25 P1 M1 M3 P3 0.273 P3 M3 M1, M9 P1, P9 0.3 P3 M3 M9 P9 0.4 P1, P3 M1, M3 M9 P9 P1 M1 1.5 P3 M3 M1 P1 1.8 P9 M9 M1, M3 P1, P3 2.25 P9 M9 M3 P3 2.5 P1, P9 M1, M9 M3 P3 3 P3 M3 4 P1, P3 M1, M3 4.5 P9 M9 M1 P1 6 P3, P9 M3, M9 M1 P1 9 P9 M9 P1, P9 M1, M9 12 P3, P9 M3, M9 13 P1, P3, P9 M1, M3, M9 VIN– VIN+ 4pF 9 M3 150k 10 M1 450k PARALLEL TO CHANGE RF, RG 450k 1 P1 450k 2 P3 150k 3 P9 50k – 6 VOUT + 4pF 450k 5 LT1991 1 10 VOUT = GAIN • (VIN+ – VIN–) GAIN = RF/RG CLASSICAL DIFFERENCE AMPLIFIER IMPLEMENTED WITH LT1991. RF = 450k, RG = 150k, GAIN = 3. ADDING THE DASHED CONNECTIONS CONNECTS THE TWO 450k RESISTORS IN PARALLEL, SO RF IS REDUCED TO 225k. GAIN BECOMES 225k/150k = 1.5. 1991 F10 Figure 10. Difference Amplifier Using the LT1991. Gain Is Set Simply by Connecting the Correct Resistors or Combinations of Resistors. Gain of 3 Is Shown, with Dashed Lines Modifying It to Gain of 1.5. Noise Gain Is Optimal. 1991fg 18 LT1991 APPLICATIONS INFORMATION VS+ VIN VIN 8 M9 9 M3 10 M1 – 1 P1 2 P3 3 P9 + VS+ 7 VCC LT1991 VEE 8 M9 9 M3 10 M1 – OUT REF 5 6 VIN VOUT 1 P1 2 P3 3 P9 + VIN 4 VS– LT1991 VEE VIN+ 1 P1 2 P3 3 P9 LT1991 VEE OUT REF 5 6 VIN– 8 M9 9 M3 10 M1 VIN+ 1 P1 2 P3 3 P9 VOUT 4 VEE VEE 6 VOUT 1 P1 2 P3 3 P9 VIN+ 4 LT1991 VEE VIN OUT REF 5 6 VOUT VIN+ 4 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE VS– 4 LT1991 OUT REF 5 6 VOUT VIN+ 4 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VIN+ 1 P1 2 P3 3 P9 VEE OUT REF 5 4 VS– GAIN = 12 LT1991 VEE OUT REF 5 6 VOUT 4 GAIN = 10 VS+ VIN– 7 VCC LT1991 7 VCC VS– GAIN = 9 8 M9 9 M3 10 M1 VOUT VS+ VIN– VS+ VIN– 6 GAIN = 4.5 VS– GAIN = 6 OUT REF 5 VS– 7 VCC VEE VOUT 4 VS+ OUT REF 5 6 VS+ 7 VCC 8 M9 9 M3 10 M1 VIN– OUT REF 5 GAIN = 2.25 GAIN = 4 7 VCC LT1991 LT1991 VS– – VS+ VIN+ VIN+ 1 P1 2 P3 3 P9 VS– GAIN = 3 1 P1 2 P3 3 P9 VOUT 7 VCC VS+ 7 VCC 8 M9 9 M3 10 M1 6 GAIN = 1 VS– VIN– OUT REF 5 4 VS+ VIN– VIN 7 VCC 8 M9 9 M3 10 M1 VS– GAIN = 0.25 8 M9 9 M3 10 M1 VS+ – 6 VOUT VIN+ 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4 VS– GAIN = 13 1991 F11 Figure 11. Many Difference Gains Are Achievable Just by Strapping the Pins 1991fg 19 LT1991 APPLICATIONS INFORMATION 8 M9 50k VIN– VIN+ RG RG 4pF 9 M3 150k VIN– RF 450k 10 M1 450k CROSSCOUPLING – VOUT + VIN+ VOUT = GAIN • (VIN+ – VIN–) GAIN = RF/RG RF 1 P1 450k 2 P3 150k 3 P9 50k – 6 VOUT + 4pF 450k 5 LT1991 CLASSICAL DIFFERENCE AMPLIFIER IMPLEMENTED WITH LT1991. RF = 450k, RG = 150k, GAIN = 3. GAIN CAN BE ADJUSTED BY "CROSS COUPLING." MAKING THE DASHED CONNECTIONS REDUCE THE GAIN FROM 3 T0 2. WHEN CROSS COUPLING, SEE WHAT IS CONNECTED TO THE VIN+ VOLTAGE. CONNECTING P3 AND M1 GIVES +3 –1 = 2. CONNECTIONS TO VIN– ARE SYMMETRIC: M3 AND P1. CLASSICAL DIFFERENCE AMPLIFIER 1991 F12 Figure 12. Another Method of Selecting Difference Gain Is “Cross-Coupling.” The Additional Method Means the LT1991 Provides All Integer Gains from 1 to 13. Difference Amplifier: Additional Integer Gains Using Cross-Coupling Figure 12 shows the basic difference amplifier as well as the LT1991 in a difference gain of 3. But notice the effect of the additional dashed connections. This is referred to as “cross-coupling” and has the effect of reducing the differential gain from 3 to 2. Using this method, additional integer gains are achievable, as shown in Table 5 below, so that all integer gains from 1 to 13 are achieved with the LT1991. Note that the equations can be written by inspection from the VIN+ connections, and that the VIN– connections are simply the opposite (swap P for M and M for P). Noise gain, bandwidth, and input impedance specifications for the various cases are also tabulated, as these are not obvious. Schematics are provided in Figure 13. VS+ VIN– 8 M9 9 M3 10 M1 VIN+ 1 P1 2 P3 3 P9 7 VCC LT1991 VEE Gain VIN+ VIN– 2 P3, M1 M3, P1 5 6* 7 8 3–1 P9, M3, M1 M9, P3, P1 9 – 3 – 1 P9, M3 M9, P3 9–3 P9, P1, M3 M9, M1, P3 9 + 1 – 3 P9, M1 M9, P1 9–1 11 P9, P3, M1 M9, M3, P1 9 + 3 – 1 6 VOUT 1 P1 2 P3 3 P9 VIN+ VS– 7 VCC LT1991 VEE VIN+ 1 P1 2 P3 3 P9 VOUT GAIN = 5 VS+ 8 M9 9 M3 10 M1 6 4 GAIN = 2 VIN– OUT REF 5 VS– VS+ LT1991 VEE OUT REF 5 8 M9 9 M3 10 M1 VIN– 7 VCC 6 VOUT 1 P1 2 P3 3 P9 VIN+ 4 VS– 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4 VS– GAIN = 7 GAIN = 8 VS+ VIN– – Noise –3dB BW RIN RIN kHz Typ kΩ Typ kΩ Equation Gain OUT REF 5 4 Table 5. Connections Using Cross-Coupling. Note That Equations Can Be Written by Inspection of the VIN+ Column + VS+ 8 M9 9 M3 10 M1 VIN– VIN+ 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4 5 70 281 141 VS– 14 32 97 49 GAIN = 11 13 35 122 49 14 32 121 44 11 38 248 50 14 32 242 37 1991 F13 Figure 13. Integer Gain Difference Amplifiers Using Cross-Coupling *Gain of 6 is better implemented as shown previously, but is included here for completeness. 1991fg 20 LT1991 APPLICATIONS INFORMATION High Voltage CM Difference Amplifiers This class of difference amplifier remains to be discussed. Figure 14 shows the basic circuit on the top. The effective input voltage range of the circuit is extended by the fact that resistors RT attenuate the common mode voltage seen by the op amp inputs. For the LT1991, the most useful resistors for RG are the M1 and P1 450kΩ resistors, because they do not have diode clamps to the supplies and therefore can be taken outside the supplies. As before, the input CM of the op amp is the limiting factor and is set by the voltage at the op amp +input, VINT. By superposition we can write: VINT = VEXT • (RF||RT)/(RG + RF||RT) + VREF • (RG||RT)/ (RF + RG||RT) + VTERM • (RF||RG)/(RT + RF||RG) Solving for VEXT : Table 6. HighV CM Connections Giving Difference Gains for the LT1991 MIN VEXT = 11 • (VEE + 1V) – VREF – 9 • VTERM = 11 • (1V) – 2.5 – 9 • 12 = –99.5V but this exceeds the 60V absolute maximum rating of the P1, M1 pins, so –60V becomes the de facto negative common mode limit. Several more examples of high CM circuits are shown in Figures 15, 16, 17 for various supplies. 2 • VLIM - VREF 5 5 • VLIM – VREF – 3 • VTERM VIN– 1 P1 M1 1 P1 M1 P3, M3 1 P1 M1 P9, M9 11 11 • VLIM – VREF – 9 • VTERM 1 P1 M1 P3||P9 14 14 • VLIM – VREF – 12 • VTERM RT M3||M9 RF VCC RG VIN– – VOUT RG VIN+ (= VEXT) + RT RT VOUT = GAIN • (VIN+ – VIN–) VEE GAIN = RF/RG RF VREF VTERM HIGH CM VOLTAGE DIFFERENCE AMPLIFIER INPUT CM TO OP AMP IS ATTENUATED BY RESISTORS RT CONNECTED TO VTERM. 7 12V 8 M9 50k 450k 4pF 9 M3 150k 10 M1 450k MAX VEXT = 11 • (VCC – 1.2V) – VREF – 9 • VTERM and: 2 VIN+ (RF + RG||RT) – VTERM • (RF||RG)/(RT + RF||RG)) = 11 • (10.8V) – 2.5 – 9 • 12 = 8.3V Max, Min VEXT (Substitute VCC – 1.2, VEE + 1 for VLIM) Gain VEXT = (1 + RG/(RF||RT)) • (VINT – VREF • (RG||RT)/ Given the values of the resistors in the LT1991, this equation has been simplified and evaluated, and the resulting equations provided in Table 6. As before, substituting VCC – 1.2 and VEE + 1 for VLIM will give the valid upper and lower common mode extremes respectively. Following are sample calculations for the case shown in Figure 14, right-hand side. Note that P9 and M9 are terminated so row 3 of Table 6 provides the equation: Noise Gain VIN+ VIN– INPUT CM RANGE = –60V TO 8.3V 1 P1 450k 2 P3 150k 3 P9 50k – 6 VOUT + 4pF 450k REF 5 2.5V LT1991 4 HIGH NEGATIVE CM VOLTAGE DIFFERENCE AMPLIFIER IMPLEMENTED WITH LT1991. RF = 450k, RG = 450k, RT 50k, GAIN = 1 VTERM = VCC = 12V, VREF = 2.5V, VEE = GROUND. 1991 F14 Figure 14. Extending CM Input Range 1991fg 21 LT1991 APPLICATIONS INFORMATION 3V 8 M9 9 M3 10 M1 VIN– 1 P1 2 P3 3 P9 VIN+ 3V 7 VCC 6 VOUT OUT REF 5 1.25V LT1991 VEE VIN– VIN+ 4 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VCM = 0.8V TO 2.35V 7 VCC LT1991 VEE VIN– 1 P1 2 P3 3 P9 VIN+ OUT REF 5 6 VIN– VOUT 6 VOUT OUT REF 5 1.25V LT1991 VEE VIN– VIN+ 4 1 P1 2 P3 3 P9 7 VCC LT1991 VEE VEE 4 3V 3V 7 VCC 6 VOUT OUT REF 5 1.25V OUT REF 5 6 VOUT 3V VCM = –1V TO 0.6V VDM <–40mV VCM = 2V TO 3.6V VDM > 40mV 8 M9 9 M3 10 M1 7 VCC LT1991 1 P1 2 P3 3 P9 VIN+ 4 3V 8 M9 9 M3 10 M1 3V 8 M9 9 M3 10 M1 3V 8 M9 9 M3 10 M1 VIN– 1 P1 2 P3 3 P9 VIN+ 4 7 VCC 6 VOUT OUT REF 5 1.25V LT1991 VEE 4 1.25V VCM = 3.8V TO 7.75V VCM = 0V TO 4V 3V 8 M9 9 M3 10 M1 VIN– 1 P1 2 P3 3 P9 VIN+ VEE 3V 3V 7 VCC LT1991 VCM = –5V TO –1.25V 6 VOUT OUT REF 5 1.25V VIN– VIN+ 4 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE 6 VOUT OUT REF 5 1.25V VIN– 3V 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VIN+ 4 7 VCC LT1991 VEE 6 VOUT OUT REF 5 1.25V 4 1.25V VCM = –1.5V TO 7.2V VCM = 9.8V TO 18.55V 3V VIN– VIN+ 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VEE 3V 3V 7 VCC LT1991 VCM = –17.2V TO –8.45V 6 VOUT OUT REF 5 1.25V 4 VIN– VIN+ 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE 6 VOUT OUT REF 5 1.25V 4 VIN– VIN+ 3V 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE 6 VOUT OUT REF 5 1.25V 4 1.25V VCM = –2.25V TO 8.95V VCM = 12.75V TO 23.95V VCM = –23.2V TO –12V 1991 F15 Figure 15. Common Mode Ranges for Various LT1991 Configurations on VS = 3V, 0V; with Gain = 1 1991fg 22 LT1991 APPLICATIONS INFORMATION 5V 8 M9 9 M3 10 M1 VIN– 1 P1 2 P3 3 P9 VIN+ 5V 7 VCC LT1991 OUT REF 5 2.5V VEE 6 VIN– VOUT VIN+ 4 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VCM = –0.5V TO 5.1V 7 VCC LT1991 VEE VIN– 1 P1 2 P3 3 P9 VIN+ OUT REF 5 6 VIN– VOUT LT1991 OUT REF 5 2.5V VEE 6 VIN– VOUT VIN+ 4 1 P1 2 P3 3 P9 7 VCC LT1991 VEE VEE 4 5V 5V 7 VCC 6 OUT REF 5 VOUT 3V VCM = –3V TO 2.6V VDM <–40mV VCM = 2V TO 7.6V VDM > 40mV 8 M9 9 M3 10 M1 7 VCC LT1991 1 P1 2 P3 3 P9 VIN+ 4 5V 8 M9 9 M3 10 M1 5V 8 M9 9 M3 10 M1 OUT REF 5 2.5V 6 VIN– VOUT 5V 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VIN+ 4 7 VCC LT1991 OUT REF 5 2.5V VEE 6 VOUT 4 2.5V VCM = 2.5V TO 16.5V VCM = –5V TO 9V 5V 8 M9 9 M3 10 M1 VIN– 1 P1 2 P3 3 P9 VIN+ VEE 5V 5V 7 VCC LT1991 VCM = –12.5V TO 1.5V OUT REF 5 2.5V 6 VIN– VOUT VIN+ 4 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 2.5V 6 VIN– VOUT 5V 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VIN+ 4 7 VCC LT1991 VEE OUT REF 5 2.5V 6 VOUT 4 2.5V VCM = –14V TO 16.8V VCM = 8.5V TO 39.3V 5V VIN– 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VIN+ VEE 5V 5V 7 VCC LT1991 VCM = –36.5V TO –5.7V OUT REF 5 2.5V 4 6 VIN– VOUT VIN+ 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 2.5V 4 6 VIN– VOUT VIN+ 5V 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 2.5V 6 VOUT 4 2.5V VCM = –18.5V TO 20.7V VCM = 11.5V TO 50.7V VCM = –48.5V TO –9.3V 1991 F16 Figure 16. Common Mode Ranges for Various LT1991 Configurations on VS = 5V, 0V; with Gain = 1 1991fg 23 LT1991 APPLICATIONS INFORMATION 5V VIN– VIN+ 8 M9 9 M3 10 M1 5V 7 VCC LT1991 1 P1 2 P3 3 P9 OUT REF 5 VEE 6 VIN– VOUT 8 M9 9 M3 10 M1 4 –5V 7 VCC LT1991 1 P1 2 P3 3 P9 VIN+ VEE 4 5V VIN– 1 P1 2 P3 3 P9 VIN+ 2.5V LT1991 OUT REF 5 VEE 6 8 M9 9 M3 10 M1 VIN– VOUT 4 VEE 1 P1 2 P3 3 P9 LT1991 VEE OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 VIN+ 4 –5V –5V 1 P1 2 P3 3 P9 LT1991 VEE 1 P1 2 P3 3 P9 VIN+ VEE OUT REF 5 6 VIN– VOUT 6 VIN– VOUT 1 P1 2 P3 3 P9 VIN+ 4 –5V VCM = –56V TO 53.2V –5V OUT REF 5 VEE 6 VOUT 4 5V 1 P1 2 P3 3 P9 4 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4 –5V VCM = –60V TO –3.2V 5V 7 VCC LT1991 VEE LT1991 8 M9 9 M3 10 M1 VIN+ 5V OUT REF 5 7 VCC 5V VCM = 1V TO 60V 7 VCC –5V –5V LT1991 8 M9 9 M3 10 M1 VOUT VCM = –35V TO 4V 7 VCC 5V VIN+ VOUT –5V VCM = –44V TO 41.8V VIN– 6 VIN– 5V VIN– 6 5V –5V 8 M9 9 M3 10 M1 4 8 M9 9 M3 10 M1 VCM = –5V TO 34V 7 VCC 8 M9 9 M3 10 M1 OUT REF 5 OUT REF 5 VEE 5V 4 –5V LT1991 1 P1 2 P3 3 P9 VIN+ 7 VCC –5V VCM = –13V TO 2.6V VDM <–40mV 7 VCC 5V VIN+ VOUT –5V LT1991 1 P1 2 P3 3 P9 VIN+ VCM = –20V TO 19V VIN– 6 5V 7 VCC 8 M9 9 M3 10 M1 OUT REF 5 VIN– –5V VCM = –3V TO 12.6V VDM > 40mV VCM = –8V TO 7.6V 8 M9 9 M3 10 M1 5V 8 M9 9 M3 10 M1 OUT REF 5 4 –5V VCM = 4V TO 60V 6 VIN– VOUT VIN+ 5V 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4 –5V VCM = –60V TO –6.8V 1991 F17 Figure 17. Common Mode Ranges for Various LT1991 Configurations on VS = ±5V, with Gain = 1 1991fg 24 LT1991 TYPICAL APPLICATIONS Micropower AV = 10 Instrumentation Amplifier 10 VM 9 8 7 6 VOUT + 1/2 LT6011 – 4pF – VP + + LT1991 1/2 LT6011 – 4pF 1 2 3 4 5 1991 TA02 1991fg 25 LT1991 PACKAGE DESCRIPTION DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699) 0.675 ±0.05 3.50 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.38 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 6 3.00 ±0.10 (4 SIDES) 0.38 ± 0.10 10 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) (DD10) DFN 1103 5 0.200 REF 1 0.25 ± 0.05 0.50 BSC 0.75 ±0.05 0.00 – 0.05 2.38 ±0.10 (2 SIDES) BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 1991fg 26 LT1991 PACKAGE DESCRIPTION MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.50 0.305 ± 0.038 (.0197) (.0120 ± .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 10 9 8 7 6 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 4.90 ± 0.152 (.193 ± .006) DETAIL “A” 0.497 ± 0.076 (.0196 ± .003) REF 0° – 6° TYP GAUGE PLANE 1 2 3 4 5 0.53 ± 0.152 (.021 ± .006) DETAIL “A” 0.86 (.034) REF 1.10 (.043) MAX 0.18 (.007) SEATING PLANE 0.17 – 0.27 (.007 – .011) TYP 0.50 (.0197) BSC 0.127 ± 0.076 (.005 ± .003) MSOP (MS) 0603 NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 1991fg Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 27 LT1991 TYPICAL APPLICATION Bidirectional Current Source Single Supply AC Coupled Amplifier VS+ 8 M9 9 M3 10 M1 VIN– VIN+ R2* 10k 1 P1 2 P3 3 P9 VS = 2.7V TO 36V 8 M9 9 M3 10 M1 7 1μF 6 LT1991 R1 10k 5 VCC 0.1μF VIN 4 1 P1 2 P3 3 P9 V + – VIN– ILOAD = IN 10kΩ VS– 7 6 LT1991 VOUT 5 4 GAIN = 12 BW = 7Hz TO 32kHz *SHORT R2 FOR LOWEST OUTPUT OFFSET CURRENT. INCLUDE R2 FOR HIGHEST OUTPUT IMPEDANCE. 1991 TA03 Ultra-Stable Precision Attenuator Analog Level Adaptor 5V 8 M9 9 M3 10 M1 5V 8 M9 9 M3 10 M1 VIN = 14V to 53V 1 P1 2 P3 3 P9 7 6 LT1991 VOUT = VIN 13 REF 5 1 P1 2 P3 3 P9 ± 10VIN 4 LT1790 –2.5 5V 1μF 7 6 LT1991 0-4VOUT REF 5 4 –5V 6 4 2 1991 TA04 1 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1990 High Voltage, Gain Selectable Difference Amplifier ±250V Common Mode, Micropower, Pin Selectable Gain = 1, 10 LT1991 Precision Gain Selectable Difference Amplifier Micropower, Pin Selectable Gain = –13 to 14 LT1995 High Speed, Gain Selectable Difference Amplifier 30MHz, 1000V/μs, Pin Selectable Gain = –7 to 8 LT6010/LT6011/LT6012 Single/Dual/Quad 135μA 14nV/√Hz Rail-to-Rail Out Precision Op Amp Similar Op Amp Performance as Used in LT1991 Difference Amplifier LT6013/LT6014 Single/Dual 145μA 8nV/√Hz Rail-to-Rail Out Precision Op Amp Lower Noise A V ≥ 5 Version of LT1991 Type Op Amp LTC6910-X Programmable Gain Amplifiers 3 Gain Configurations, Rail-to-Rail Input and Output 1991fg 28 Linear Technology Corporation LT 1007 REV G • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2006