LT1028CS8

LT1028/LT1128 Ultralow Noise Precision High Speed Op Amps FEATURES s DESCRIPTIO s s s s s s s Voltage Noise 1.1nV/√Hz Max at 1kHz 0.85nV/√Hz Typ at 1kHz 1.0nV/√Hz Typ at 10Hz 35nVP-P Typ, 0.1Hz to 10Hz Voltage and Current Noise 100% Tested Gain-Bandwidth Product LT1028: 50MHz Min LT1128: 13MHz Min Slew Rate LT1028: 11V/µs Min LT1128: 5V/µs Min Offset Voltage: 40µV Max Drift with Temperature: 0.8µV/°C Max Voltage Gain: 7 Million Min Available in 8-Pin SO Package The LT®1028(gain of –1 stable)/LT1128(gain of +1 stable) achieve a new standard of excellence in noise performance with 0.85nV/√Hz 1kHz noise, 1.0nV/√Hz 10Hz noise. This ultralow noise is combined with excellent high speed specifications (gain-bandwidth product is 75MHz for LT1028, 20MHz for LT1128), distortion-free output, and true precision parameters (0.1µV/°C drift, 10µV offset voltage, 30 million voltage gain). Although the LT1028/ LT1128 input stage operates at nearly 1mA of collector current to achieve low voltage noise, input bias current is only 25nA. The LT1028/LT1128’s voltage noise is less than the noise of a 50Ω resistor. Therefore, even in very low source impedance transducer or audio amplifier applications, the LT1028/LT1128’s contribution to total system noise will be negligible. , LTC and LT are registered trademarks of Linear Technology Corporation APPLICATIO S s s s s s s s Low Noise Frequency Synthesizers High Quality Audio Infrared Detectors Accelerometer and Gyro Amplifiers 350Ω Bridge Signal Conditioning Magnetic Search Coil Amplifiers Hydrophone Amplfiers TYPICAL APPLICATIO 10 VOLTAGE NOISE DENSITY (nV/√Hz) Flux Gate Amplifier DEMODULATOR SYNC + LT1028 SQUARE WAVE DRIVE 1kHz FLUX GATE TYPICAL SCHONSTEDT #203132 OUTPUT TO DEMODULATOR 1k 1 1/f CORNER = 3.5Hz – 50Ω 0.1 0.1 1028/1128 TA01 U Voltage Noise vs Frequency MAXIMUM VS = ±15V TA = 25°C 1/f CORNER = 14Hz TYPICAL 1 10 100 FREQUENCY (Hz) 1k 1028/1128 TA02 U U 1 LT1028/LT1128 ABSOLUTE AXI U RATI GS (Note 1) Operating Temperature Range LT1028/LT1128AM, M (OBSOLETE) . – 55°C to 125°C LT1028/LT1128AC, C (Note 11) ......... – 40°C to 85°C Storage Temperature Range All Devices ........................................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec.)................. 300°C Supply Voltage –55°C to 105°C ................................................ ± 22V 105°C to 125°C ................................................ ±16V Differential Input Current (Note 9) ...................... ± 25mA Input Voltage ............................ Equal to Supply Voltage Output Short Circuit Duration .......................... Indefinite PACKAGE/ORDER I FOR ATIO TOP VIEW VOS TRIM 8 VOS TRIM 1 – ORDER PART NUMBER 7 V+ 6 OUT 5 OVERCOMP –IN 2 + +IN 3 4 V– (CASE) LT1028AMH LT1028MH LT1028ACH LT1028CH H PACKAGE 8-LEAD TO-5 METAL CAN TJMAX = 175°C, θJA = 140°C/W, θJC = 40°C/W OBSOLETE PACKAGE Consider S8 or N8 Packages for Alternate Source TOP VIEW VOS TRIM 1 –IN 2 +IN 3 V– 4 V 8 OS TRIM 7 V+ 6 OUT ORDER PART NUMBER LT1028ACN8 LT1028CN8 LT1128ACN8 LT1128CN8 LT1028AMJ8 LT1028MJ8 LT1028ACJ8 LT1028CJ8 LT1128AMJ8 LT1128MJ8 LT1128CJ8 TOP VIEW NC 1 NC 2 TRIM 3 –IN 4 +IN 5 V– 6 – + – + 5 OVERCOMP N8 PACKAGE 8-LEAD PLASTIC DIP TJMAX = 130°C, θJA = 130°C/W J8 PACKAGE 8-LEAD CERAMIC DIP TJMAX = 165°C, θJA = 100°C/W OBSOLETE PACKAGE Consider N8 Package for Alternate Source Consult LTC Marketing for parts specified with wider operating temperature ranges. 2 U U W WW U W ORDER PART NUMBER TOP VIEW VOS TRIM 1 –IN 2 +IN 3 V– 4 8 – + 7 6 5 VOS TRIM V+ OUT OVERCOMP LT1028CS8 LT1128CS8 S8 PART MARKING 1028 1128 S8 PACKAGE 8-LEAD PLASTIC SOIC TJMAX = 135°C, θJA = 140°C/W ORDER PART NUMBER 16 NC 15 NC 14 TRIM 13 V + 12 OUT 11 OVERCOMP 10 NC 9 NC LT1028CSW NC 7 NC 8 SW PACKAGE 16-LEAD PLASTIC SOL TJMAX = 140°C, θJA = 130°C/W NOTE: THIS DEVICE IS NOT RECOMMENDED FOR NEW DESIGNS LT1028/LT1128 ELECTRICAL CHARACTERISTICS VS = ±15V, TA = 25°C, unless otherwise noted. LT1028AM/AC LT1128AM/AC SYMBOL VOS ∆VOS ∆Time IOS IB en PARAMETER Input Offset Voltage Long Term Input Offset Voltage Stability Input Offset Current Input Bias Current Input Noise Voltage Input Noise Voltage Density In Input Noise Current Density Input Resistance Common Mode Differential Mode Input Capacitance Input Voltage Range Common Mode Rejection Ratio Power Supply Rejection Ratio Large-Signal Voltage Gain CONDITIONS (Note 2) (Note 3) VCM = 0V VCM = 0V 0.1Hz to 10Hz (Note 4) fO = 10Hz (Note 5) fO = 1000Hz, 100% tested fO = 10Hz (Note 4 and 6) fO = 1000Hz, 100% tested MIN TYP 10 0.3 12 ±25 35 1.00 0.85 4.7 1.0 300 20 5 ±11.0 ±12.2 114 126 117 133 7.0 30.0 5.0 20.0 3.0 15.0 ±12.3 ±13.0 ±11.0 ±12.2 11.0 15.0 5.0 6.0 50 75 13 20 80 7.4 MAX 40 LT1028M/C LT1128M/C MIN TYP 20 0.3 18 ±30 35 1.0 0.9 4.7 1.0 300 20 5 ±12.2 126 132 30.0 20.0 15.0 ±13.0 ±12.2 15.0 6.0 75 20 80 7.6 MAX 80 UNITS µV µV/Mo nA nA nVP-P nV/√Hz nV/√Hz pA/√Hz pA/√Hz MΩ kΩ pF V dB dB V/µV V/µV V/µV V V V/ µs V/ µs MHz MHz Ω mA 50 ±90 75 1.7 1.1 10.0 1.6 100 ±180 90 1.9 1.2 12.0 1.8 CMRR PSRR AVOL VOUT SR GBW ZO IS Maximum Output Voltage Swing Slew Rate Gain-Bandwidth Product Open-Loop Output Impedance Supply Current VCM = ±11V VS = ±4V to ±18V RL ≥ 2k, VO = ±12V RL ≥ 1k, VO = ±10V RL ≥ 600Ω, VO = ±10V RL ≥ 2k RL ≥ 600Ω AVCL = –1 AVCL = –1 fO = 20kHz (Note 7) fO = 200kHz (Note 7) VO = 0, IO = 0 LT1028 LT1128 LT1028 LT1128 ±11.0 110 110 5.0 3.5 2.0 ±12.0 ±10.5 11.0 4.5 50 11 9.5 10.5 –55°C ≤ TA ≤ 125°C. VS = ±15V, unless otherwise noted. ELECTRICAL CHARACTERISTICS SYMBOL VOS ∆VOS ∆Temp IOS IB CMRR PSRR AVOL VOUT IS PARAMETER Input Offset Voltage Average Input Offset Drift Input Offset Current Input Bias Current Input Voltage Range Common Mode Rejection Ratio Power Supply Rejection Ratio Large-Signal Voltage Gain Maximum Output Voltage Swing Supply Current CONDITIONS (Note 2) (Note 8) VCM = 0V VCM = 0V The q denotes the specifications which apply over the temperature range LT1028AM LT1128AM MIN q q q q q q q q q q LT1028M LT1128M MAX 120 0.8 MIN TYP 45 0.25 30 ± 50 ±11.7 120 130 14.0 10.0 ±11.6 9.0 MAX 180 1.0 180 ± 300 UNITS µV µV/ °C nA nA V dB dB V/µV V/µV V mA TYP 30 0.2 VCM = ±10.3V VS = ±4.5V to ±16V RL ≥ 2k, VO = ±10V RL ≥ 1k, VO = ±10V RL ≥ 2k 25 ± 40 ±10.3 ±11.7 106 122 110 130 3.0 14.0 2.0 10.0 ±10.3 ±11.6 8.7 90 ±150 ±10.3 100 104 2.0 1.5 ±10.3 11.5 13.0 3 LT1028/LT1128 0°C ≤ TA ≤ 70°C. VS = ±15V, unless otherwise noted. ELECTRICAL CHARACTERISTICS PARAMETER Input Offset Voltage Average Input Offset Drift Input Offset Current Input Bias Current Input Voltage Range Common Mode Rejection Ratio Power Supply Rejection Ratio Large-Signal Voltage Gain Maximum Output Voltage Swing Supply Current CONDITIONS (Note 2) (Note 8) VCM = 0V VCM = 0V The q denotes the specifications which apply over the temperature range LT1028AC LT1128AC LT1028C LT1128C MAX 80 0.8 65 ± 120 ±10.5 106 107 3.0 2.5 ±11.5 ±9.0 10.5 MIN TYP 30 0.2 22 ±40 ±12.0 124 132 25.0 18.0 ±12.7 ±10.5 8.2 MAX 125 1.0 130 ± 240 UNITS µV µV/ °C nA nA V dB dB V/µV V/µV V V mA SYMBOL VOS ∆V OS ∆Temp IOS IB CMRR PSRR AVOL VOUT IS MIN q q q q q q q q q q TYP 15 0.1 VCM = ±10.5V VS = ± 4.5V to ±18V RL ≥ 2k, VO = ±10V RL ≥ 1k, VO = ±10V RL ≥ 2k RL ≥ 600Ω (Note 10) 15 ±30 ±10.5 ±12.0 110 124 114 132 5.0 25.0 4.0 18.0 ±11.5 ±12.7 ±9.5 ±11.0 8.0 11.5 ELECTRICAL CHARACTERISTICS SYMBOL VOS ∆V OS ∆Temp IOS IB CMRR PSRR AVOL VOUT IS PARAMETER Input Offset Voltage Average Input Offset Drift Input Offset Current Input Bias Current Input Voltage Range Common Mode Rejection Ratio Power Supply Rejection Ratio Large-Signal Voltage Gain Maximum Output Voltage Swing Supply Current CONDITIONS The q denotes the specifications which apply over the temperature range – 40°C ≤ TA ≤ 85°C. VS = ±15V, unless otherwise noted. (Note 11) LT1028C LT1028AC LT1128C LT1128AC MIN q q q q q q q q q q (Note 8) VCM = 0V VCM = 0V VCM = ±10.5V VS = ±4.5V to ±18V RL ≥ 2k, VO = ±10V RL ≥ 1k, VO = ±10V RL ≥ 2k TYP 20 0.2 MAX 95 0.8 80 ±140 MIN TYP 35 0.25 28 ±45 ±11.8 123 131 20.0 14.0 ±12.5 8.7 MAX 150 1.0 160 ±280 UNITS µV µV/ °C nA nA V dB dB V/µV V/µV V mA 20 ±35 ±10.4 ±11.8 108 123 112 131 4.0 20.0 3.0 14.0 ±11.0 ±12.5 8.5 ±10.4 102 106 2.5 2.0 ±11.0 11.0 12.5 Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Input Offset Voltage measurements are performed by automatic test equipment approximately 0.5 sec. after application of power. In addition, at TA = 25°C, offset voltage is measured with the chip heated to approximately 55°C to account for the chip temperature rise when the device is fully warmed up. Note 3: Long Term Input Offset Voltage Stability refers to the average trend line of Offset Voltage vs. Time over extended periods after the first 30 days of operation. Excluding the initial hour of operation, changes in VOS during the first 30 days are typically 2.5µV. Note 4: This parameter is tested on a sample basis only. Note 5: 10Hz noise voltage density is sample tested on every lot with the exception of the S8 and S16 packages. Devices 100% tested at 10Hz are available on request. Note 6: Current noise is defined and measured with balanced source resistors. The resultant voltage noise (after subtracting the resistor noise on an RMS basis) is divided by the sum of the two source resistors to obtain current noise. Maximum 10Hz current noise can be inferred from 100% testing at 1kHz. Note 7: Gain-bandwidth product is not tested. It is guaranteed by design and by inference from the slew rate measurement. Note 8: This parameter is not 100% tested. Note 9: The inputs are protected by back-to-back diodes. Current-limiting resistors are not used in order to achieve low noise. If differential input voltage exceeds ±1.8V, the input current should be limited to 25mA. Note 10: This parameter guaranteed by design, fully warmed up at TA = 70°C. It includes chip temperature increase due to supply and load currents. Note 11: The LT1028/LT1128 are designed, characterized and expected to meet these extended temperature limits, but are not tested at –40°C and 85°C. Guaranteed I grade parts are available. Consult factory. 4 LT1028/LT1128 TYPICAL PERFOR A CE CHARACTERISTICS 10Hz Voltage Noise Distribution 180 160 140 NUMBER OF UNITS 158 148 120 100 80 60 40 20 0 0.6 8 70 57 RMS VOLTAGE NOISE (µV) VS = ±15V TA = 25°C 500 UNITS MEASURED FROM 4 RUNS 28 74 3 2 2 2 12 3 21 1 1 0.8 1.0 1.2 1.4 1.6 1.8 2.0 VOLTAGE NOISE DENSITY (nV/√Hz) LT1020/1120 • TPC01 Total Noise vs Matched Source Resistance 100 RS TOTAL NOISE DENSITY (nV/√Hz) RS + TOTAL NOISE DENSITY (nV/√Hz) – CURRENT NOISE DENSITY (pA/√Hz) 10 AT 10Hz 1 2 RS NOISE ONLY VS = ±15V TA = 25°C 0.1 1 10 30 100 300 1k 3k 3 MATCHED SOURCE RESISTANCE (Ω) 10k AT 1kHz LT1028/1128 • TPC04 0.1Hz to 10Hz Voltage Noise VS = ±15V TA = 25°C RMS VOLTAGE DENSITY (nV/√Hz) 10nV 0 2 6 4 TIME (SEC) LT1028/1128 • TPC07 UW 2.2 8 10 Wideband Noise, DC to 20kHz 10 Wideband Voltage Noise (0.1Hz to Frequency Indicated) VS = ±15V TA = 25°C 1 0.1 VERTICAL SCALE = 0.5µV/DIV HORIZONTAL SCALE = 0.5ms/DIV 0.01 100 1k 100k 10k BANDWIDTH (Hz) 1M 10M LT1028/1128 • TPC03 Total Noise vs Unmatched Source Resistance 100 RS Current Noise Spectrum 100 10 10 MAXIMUM 1/f CORNER = 800Hz TYPICAL AT 10Hz 1 AT 1kHz 1 1/f CORNER = 250Hz 2 RS NOISE ONLY VS = ±15V TA = 25°C 0.1 1 10 30 100 300 1k 3k 10k 3 UNMATCHED SOURCE RESISTANCE (Ω) LT1028/1128 • TPC05 0.1 10 100 1k FREQUENCY (Hz) 10k LT1028/1128 • TPC06 0.01Hz to 1Hz Voltage Noise VS = ±15V TA = 25°C 2.0 Voltage Noise vs Temperature VS = ±15V 1.6 1.2 AT 10Hz 0.8 AT 1kHz 10nV O.4 0 20 60 40 TIME (SEC) 80 100 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 LT1028/1128 • TPC08 LT1028/1128 • TPC09 5 LT1028/LT1128 TYPICAL PERFOR A CE CHARACTERISTICS Distribution of Input Offset Voltage 20 18 16 14 UNITS (%) 12 10 8 6 4 2 0 –50 –40 –30 –20 –10 0 10 20 30 40 50 OFFSET VOLTAGE (µV) LT1028/1128 • TPC10 30 OFFSET VOLTAGE CHANGE (µV) OFFSET VOLTAGE (µV) VS = ±15V TA = 25°C 800 UNITS TESTED FROM FOUR RUNS Warm-Up Drift 24 CHANGE IN OFFSET VOLTAGE (µV) 20 16 METAL CAN (H) PACKAGE 12 8 4 0 0 1 2 3 4 TIME AFTER POWER ON (MINUTES) 5 DUAL-IN-LINE PACKAGE PLASTIC (N) OR CERDIP (J) INPUT BIAS AND OFFSET CURRENTS (nA) VS = ±15V TA = 25°C INPUT BIAS CURRENT (nA) LT1028/1128 • TPC13 Voltage Noise vs Supply Voltage 1.5 RMS VOLTAGE NOISE DENSITY (nV/√Hz) 10 TA = 25°C 8 SUPPLY CURRENT (mA) VS = ±15V VS = ±5V SHORT-CIRCUIT CURRENT (mA) SINKING SOURCING 1.25 1.0 AT 10Hz AT 1kHz 0.75 0.5 0 ±5 ±10 ±15 SUPPLY VOLTAGE (V) LT1028/1128 • TPC16 6 UW Offset Voltage Drift with Temperature of Representative Units 50 40 VS = ±15V Long-Term Stability of Five Representative Units 10 8 6 4 2 0 –2 –4 –6 –8 VS = ±15V TA = 25°C t = 0 AFTER 1 DAY PRE-WARM UP 20 10 0 –10 –20 –30 –40 –50 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 –10 0 1 3 2 TIME (MONTHS) 4 5 LT1028/1128 • TPC11 LT1028/1128 • TPC12 Input Bias and Offset Currents Over Temperature 60 50 40 30 BIAS CURRENT 20 10 0 –50 –25 OFFSET CURRENT VS = ±15V VCM = 0V 100 80 60 40 20 0 –20 –40 –60 100 125 Bias Current Over the Common Mode Range RCM = 20V ≈ 300MΩ VS = ±15V 65nA TA = 25°C POSITIVE INPUT CURRENT (UNDERCANCELLED) DEVICE NEGATIVE INPUT CURRENT (OVERCANCELLED) DEVICE 10 5 –10 0 –5 COMMON MODE INPUT VOLTAGE (V) 15 50 25 75 0 TEMPERATURE (˚C) –80 –15 LT1028/1128 • TPC14 LT1028/1128 • TPC15 Supply Current vs Temperature 50 40 30 20 10 0 –10 –20 –30 –40 –50 50 25 0 75 TEMPERATURE (°C) 100 125 9 Output Short-Circuit Current vs Time –50°C 25°C 125°C VS = ±15V 7 6 5 4 3 2 1 125°C 25°C –50°C ±20 0 –50 –25 3 2 0 1 TIME FROM OUTPUT SHORT TO GROUND (MINUTES) LT1028/1128 • TPC18 LT1028/1128 • TPC17 LT1028/LT1128 TYPICAL PERFOR A CE CHARACTERISTICS Voltage Gain vs Frequency 160 140 120 VS = ±15V TA = 25°C RL = 2k OVERSHOOT (%) LT1128 80 60 40 20 0 –20 0.01 0.1 1 LT1028 40 30 GAIN 20 10 0 VS = ±15V TA = 25°C CL = 10pF 100k 1M 10M FREQUENCY (Hz) 40 30 20 10 0 –10 100M 50 40 30 20 10 0 10 AV = –1, RS = 2k AV = –10 RS = 200Ω AV = –100 RS = 20Ω VS = ±15V TA = 25°C 10000 10 100 1k 10k 100k 1M 10M 100M FREQUENCY (Hz) LT1028/1128 • TPC19 –10 10k LT1028/1128 • TPC20 Gain Error vs Frequency Closed-Loop Gain = 1000 1 TYPICAL PRECISION OP AMP 0.1 VOLTAGE GAIN (dB) LT1128 Gain Phase vs Frequency 70 60 PHASE 70 60 PHASE MARGIN (DEG) LT1128 Capacitance Load Handling 80 70 – 30pF 2k RS GAIN ERROR (%) LT1128 50 40 30 20 GAIN 10 50 40 30 20 10 VS = ±15V TA = 25°C CL = 10pF 100k 1M 10M FREQUENCY (Hz) 0 –10 100M 60 OVERSHOOT (%) 50 40 30 20 10 0 10 AV = –1, RS = 2k AV = –10 RS = 200Ω VS = ±15V TA = 25°C VO = 10mVP-P 10000 LT1028 0.01 0.001 0.1 GAIN ERROR = CLOSED-LOOP GAIN OPEN-LOOP GAIN 10 1 FREQUENCY (Hz) 100 LT1028/1128 • TPC22 0 –10 10k AV = –100, RS = 20Ω LT1028/1128 • TPC23 Voltage Gain vs Supply Voltage 100 TA = 25°C 100 Voltage Gain vs Load Resistance PEAK-TO-PEAK OUTPUT VOLTAGE (V) VS = ±15V 30 25 20 15 Maximum Undistorted Output vs Frequency VS = ±15V TA = 25°C RL = 2k VOLTAGE GAIN (V/µV) VOLTAGE GAIN (V/µV) RL = 2k RL = 600Ω TA = – 55°C 10 TA = 25°C TA = 125°C 10 10 5 1 0 1 ±5 ±10 ±15 SUPPLY VOLTAGE (V) ±20 0.1 ILMAX = 35mA AT –55°C = 27mA AT 25°C = 16mA AT 125°C 1 LOAD RESISTANCE (kΩ) 10 10k LT`1028/1128 • TPC25 LT1028/1128 • TPC26 + + 100 PHASE MARGIN (DEG) VOLTAGE GAIN (dB) VOLTAGE GAIN (dB) – UW LT1028 Gain, Phase vs Frequency 70 PHASE 60 50 60 50 70 80 70 60 LT1028 Capacitance Load Handling 30pF 2k RS CL 100 1000 CAPACITIVE LOAD (pF) LT1028/1128 • TPC21 CL 100 1000 CAPACITIVE LOAD (pF) LT1028/1128 • TPC 24 LT1128 LT1028 100k 1M FREQUENCY (Hz) 10M LT1028/1128 • TPC27 7 LT1028/LT1128 TYPICAL PERFOR A CE CHARACTERISTICS LT1028 Large-Signal Transient Response 50mV SLEW RATE (V/µs) 20mV/DIV 10V 5V/DIV –10V –50mV 1µs/DIV AV = –1, RS = RF = 2k, C F = 15pF LT1128 Large-Signal Transient Response 50mV 10V SLEW RATE (V/µs) 0V –10V –50mV 2µs/DIV AV = –1, RS = RF = 2k, C F = 30pF Closed-Loop Output Impedance 100 IO = 1mA VS = ±15V TA = 25°C AV = 1000 1 LT1128 LT1028 100 OUTPUT IMPEDANCE (Ω) 10 SLEW RATE (V/µs) SLEW RATE (V/µs) 0.1 LT1128 LT1028 AV = 5 0.01 0.001 10 100 10k 1k FREQUENCY (Hz) 100k LT1028/1128 • TPC34 8 UW 1M LT1028 Small-Signal Transient Response 18 17 16 15 14 13 LT1028 Slew Rate, Gain-Bandwidth Product Over Temperature GAIN-BANDWIDTH PRODUCT (fO = 20kHz), (MHz) VS = ±15V GBW FALL RISE 90 80 70 60 50 40 30 125 0.2µs/DIV AV = –1, RS = RF = 2k CF = 15pF, CL = 80pF 12 –50 –25 50 25 75 0 TEMPERATURE (˚C) 100 LT1028/1128 • TPC30 LT1128 Small-Signal Transient Response 9 8 7 LT1128 Slew Rate, Gain-Bandwidth Product Over Temperature GAIN-BANDWIDTH PRODUCT (fO = 200kHz), (MHz) FALL RISE 6 5 4 3 2 10 GBW 20 30 0V 0.2µs/DIV AV = 1, C L = 10pF 1 0 –50 –25 75 50 25 0 TEMPERATURE (°C) 100 125 LT1028/1128 • TPC33 LT1128 Slew Rate, Gain-Bandwidth Product vs Over-Compensation Capacitor 1k 100 LT1028 Slew Rate, Gain-Bandwidth Product vs Over-Compensation Capacitor 10k 10 10 GBW SLEW RATE SLEW 100 10 GBW 1k GAIN AT 200kHz GAIN AT 20kHz 1 10 1 COC FROM PIN 5 TO PIN 6 VS = ±15V TA = 25°C 100 0.1 1 1 10 100 1000 10000 OVER-COMPENSATION CAPACITOR (pF) LT1028/1128 • TPC35 0.1 1 10 10 100 1000 10000 OVER-COMPENSATION CAPACITOR (pF) LT1028/1128 • TPC36 LT1028/LT1128 TYPICAL PERFOR A CE CHARACTERISTICS Common Mode Limit Over Temperature V+ –1 COMMON MODE LIMIT (V) REFERRED TO POWER SUPPLY COMMON MODE REJECTION RATIO (dB) POWER SUPPLY REJECTION RATIO (dB) –2 –3 –4 VS = ±5V VS = ±15V 4 3 2 1 V – VS = ±5V TO ±15V –50 –25 50 25 0 75 TEMPERATURE (°C) LT1028/1128 • TPC37 LT1028 Total Harmonic Distortion vs Frequency and Load Resistance 0.1 TOTAL HARMONIC DISTORTION (%) 0.1 TOTAL HARMONIC DISTORTION (%) AV = 1000 RL = 600Ω 0.01 NOISE VOLTAGE DENSITY (nV/÷Hz) AV = 1000 RL = 2k 0.01 AV = –1000 RL = 2k AV = 1000 RL = 600Ω VO = 20VP-P VS = ±15V TA = 25°C 1 10 FREQUENCY (kHz) 100 LT1028/1128 • TPC40 0.001 LT1128 Total Harmonic Distortion vs Frequency and Load Resistance 1.0 TOTAL HARMONIC DISTORTION (%) TOTAL HARMONIC DISTORTION (%) 0.1 0.1 AV = 1000 RL = 2k 0.01 0.001 1.0 UW 100 Common Mode Rejection Ratio vs Frequency 140 120 100 LT1128 80 60 40 20 0 10 100 100k 10k 1k FREQUENCY (Hz) 1M 10M LT1028 VS = ±15V TA = 25°C 160 140 120 100 80 60 40 20 Power Supply Rejection Ratio vs Frequency VS = ±15V TA = 25°C NEGATIVE SUPPLY POSITIVE SUPPLY 125 0 0.1 1 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz) LT1028/1128 • TPC39 LT1028/1128 • TPC38 LT1028 Total Harmonic Distortion vs Closed-Loop Gain 10 VO = 20VP-P f = 1kHz VS = ±15V TA = 25°C RL = 10k NON-INVERTING GAIN High Frequency Voltage Noise vs Frequency 1.0 0.001 INVERTING GAIN MEASURED EXTRAPOLATED 10 100 1k 10k CLOSED LOOP GAIN 100k 0.0001 0.1 10k 100k FREQUENCY (Hz) 1M LT1028/1128 • TPC42 LT1028/1128 • TPC41 LT1128 Total Harmonic Distortion vs Closed-Loop Gain VO = 20VP-P f = 1kHz VS = ±15V TA = 25°C RL = 10k NON-INVERTING GAIN AV = 1000 RL = 600Ω 0.01 AV = –1000 RL = 2k AV = 1000 RL = 600Ω VO = 20VP-P VS = ±15V TA = 25°C 10 FREQUENCY (kHz) 100 LT1028/1128 • TPC43 0.001 INVERTING GAIN MEASURED EXTRAPOLATED 10 1k 10k 100 CLOSED LOOP GAIN 100k 0.0001 LT1028/1128 • TPC44 9 LT1028/LT1128 APPLICATI S I FOR ATIO – OISE largest term, as in the example above, and the LT1028/ LT1128’s voltage noise becomes negligible. As Req is further increased, current noise becomes important. At 1kHz, when Req is in excess of 20k, the current noise component is larger than the resistor noise. The total noise versus matched source resistance plot illustrates the above calculations. The plot also shows that current noise is more dominant at low frequencies, such as 10Hz. This is because resistor noise is flat with frequency, while the 1/f corner of current noise is typically at 250Hz. At 10Hz when Req > 1k, the current noise term will exceed the resistor noise. When the source resistance is unmatched, the total noise versus unmatched source resistance plot should be consulted. Note that total noise is lower at source resistances below 1k because the resistor noise contribution is less. When RS > 1k total noise is not improved, however. This is because bias current cancellation is used to reduce input bias current. The cancellation circuitry injects two correlated current noise components into the two inputs. With matched source resistors the injected current noise creates a common-mode voltage noise and gets rejected by the amplifier. With source resistance in one input only, the cancellation noise is added to the amplifier’s inherent noise. In summary, the LT1028/LT1128 are the optimum amplifiers for noise performance, provided that the source resistance is kept low. The following table depicts which op amp manufactured by Linear Technology should be used to minimize noise, as the source resistance is increased beyond the LT1028/LT1128’s level of usefulness. 1028/1128 AI01 Voltage Noise vs Current Noise The LT1028/LT1128’s less than 1nV/√Hz voltage noise is three times better than the lowest voltage noise heretofore available (on the LT1007/1037). A necessary condition for such low voltage noise is operating the input transistors at nearly 1mA of collector currents, because voltage noise is inversely proportional to the square root of the collector current. Current noise, however, is directly proportional to the square root of the collector current. Consequently, the LT1028/LT1128’s current noise is significantly higher than on most monolithic op amps. Therefore, to realize truly low noise performance it is important to understand the interaction between voltage noise (en), current noise (In) and resistor noise (rn). Total Noise vs Source Resistance The total input referred noise of an op amp is given by et = [en2 + rn2 + (InReq)2]1/2 where Req is the total equivalent source resistance at the two inputs, and rn = √4kTReq = 0.13√Req in nV/√Hz at 25°C As a numerical example, consider the total noise at 1kHz of the gain 1000 amplifier shown below. 100Ω 100k – 100Ω LT1028 LT1128 + Req = 100Ω + 100Ω || 100k ≈ 200Ω rn = 0.13√200 = 1.84nV√Hz en = 0.85nV√Hz In = 1.0pA/√Hz et = [0.852 + 1.842 + (1.0 × 0.2) 2]1/2 = 2.04nV/√Hz Output noise = 1000 et = 2.04µV/√Hz At very low source resistance (Req < 40Ω) voltage noise dominates. As Req is increased resistor noise becomes the 10 UU W U UO Best Op Amp for Lowest Total Noise vs Source Resistance SOURCE RESISTANCE(Ω) (Note 1) 0 to 400 400 to 4k 4k to 40k 40k to 500k 500k to 5M >5M BEST OP AMP AT LOW FREQ(10Hz) WIDEBAND(1kHz) LT1028/LT1128 LT1007/1037 LT1001 LT1012 LT1012 or LT1055 LT1055 LT1028/LT1128 LT1028/LT1128 LT1007/1037 LT1001 LT1012 LT1055 Note 1: Source resistance is defined as matched or unmatched, e.g., RS = 1k means: 1k at each input, or 1k at one input and zero at the other. LT1028/LT1128 APPLICATI S I FOR ATIO – OISE Measuring the typical 35nV peak-to-peak noise performance of the LT1028/LT1128 requires special test precautions: (a) The device should be warmed up for at least five minutes. As the op amp warms up, its offset voltage changes typically 10µV due to its chip temperature increasing 30°C to 40°C from the moment the power supplies are turned on. In the 10 second measurement interval these temperature-induced effects can easily exceed tens of nanovolts. (b) For similar reasons, the device must be well shielded from air current to eliminate the possibility of thermoelectric effects in excess of a few nanovolts, which would invalidate the measurements. (c) Sudden motion in the vicinity of the device can also “feedthrough” to increase the observed noise. A noise-voltage density test is recommended when measuring noise on a large number of units. A 10Hz noisevoltage density measurement will correlate well with a 0.1Hz to 10Hz peak-to-peak noise reading since both results are determined by the white noise and the location of the 1/f corner frequency. Noise Testing – Voltage Noise The LT1028/LT1128’s RMS voltage noise density can be accurately measured using the Quan Tech Noise Analyzer, Model 5173 or an equivalent noise tester. Care should be taken, however, to subtract the noise of the source resistor used. Prefabricated test cards for the Model 5173 set the device under test in a closed-loop gain of 31 with a 60Ω source resistor and a 1.8k feedback resistor. The noise of this resistor combination is 0.13√58 = 1.0nV/√Hz. An LT1028/LT1128 with 0.85nV/√Hz noise will read (0.852 + 1.02)1/2 = 1.31nV/√Hz. For better resolution, the resistors should be replaced with a 10Ω source and 300Ω feedback resistor. Even a 10Ω resistor will show an apparent noise which is 8% to 10% too high. The 0.1Hz to 10Hz peak-to-peak noise of the LT1028/ LT1128 is measured in the test circuit shown. The frequency response of this noise tester indicates that the 0.1Hz corner is defined by only one zero. The test time to measure 0.1Hz to 10Hz noise should not exceed 10 seconds, as this time limit acts as an additional zero to eliminate noise contributions from the frequency band below 0.1Hz. 0.1Hz to 10Hz Noise Test Circuit 0.1µF 100k GAIN (dB) – 10Ω 2k * + LT1001 + 4.7µF – 100k 0.1µF 2.2µF VOLTAGE GAIN = 50,000 * DEVICE UNDER TEST NOTE ALL CAPACITOR VALUES ARE FOR NONPOLARIZED CAPACITORS ONLY 24.3k UU 4.3k W U UO 0.1Hz to 10Hz Peak-to-Peak Noise Tester Frequency Response 100 90 80 22µF 70 60 50 40 30 0.01 SCOPE ×1 RIN = 1M 110k 0.1 1028/1128 AI02 1.0 10 FREQUENCY (Hz) 100 LT1028/1128 • AI03 11 LT1028/LT1128 APPLICATI S I FOR ATIO – OISE 10Hz voltage noise density is sample tested on every lot. Devices 100% tested at 10Hz are available on request for an additional charge. 10Hz current noise is not tested on every lot but it can be inferred from 100% testing at 1kHz. A look at the current noise spectrum plot will substantiate this statement. The only way 10Hz current noise can exceed the guaranteed limits is if its 1/f corner is higher than 800Hz and/or its white noise is high. If that is the case then the 1kHz test will fail. eno Noise Testing – Current Noise Current noise density (In) is defined by the following formula, and can be measured in the circuit shown: [eno2 – (31 × 18.4nV/√Hz)2]1/2 In = 20k × 31 1.8k 10k 60Ω – LT1028 LT1128 10k + 1028/1128 AI04 NOISE FILTER LOSS (dB) If the Quan Tech Model 5173 is used, the noise reading is input-referred, therefore the result should not be divided by 31; the resistor noise should not be multiplied by 31. 100% Noise Testing The 1kHz voltage and current noise is 100% tested on the LT1028/LT1128 as part of automated testing; the approximate frequency response of the filters is shown. The limits on the automated testing are established by extensive correlation tests on units measured with the Quan Tech Model 5173. APPLICATI General S I FOR ATIO The LT1028/LT1128 series devices may be inserted directly into OP-07, OP-27, OP-37, LT1007 and LT1037 sockets with or without removal of external nulling components. In addition, the LT1028/LT1128 may be fitted to 5534 sockets with the removal of external compensation components. Offset Voltage Adjustment The input offset voltage of the LT1028/LT1128 and its drift with temperature, are permanently trimmed at wafer testing to a low level. However, if further adjustment of VOS is necessary, the use of a 1k nulling potentiometer will not degrade drift with temperature. Trimming to a value other 12 UU U W W U U UO Automated Tester Noise Filter 10 0 –10 –20 –30 –40 –50 100 CURRENT NOISE VOLTAGE NOISE 1k 10k 100k LT1028/1128 • AI05 FREQUENCY (Hz) UO 1k 15V 1 2 INPUT 3 – + 8 76 OUTPUT LT1028 LT1128 4 –15V 1028/1128 AI06 than zero creates a drift of (VOS/300)µV/°C, e.g., if VOS is adjusted to 300µV, the change in drift will be 1µV/°C. The adjustment range with a 1k pot is approximately ±1.1mV. Offset Voltage and Drift Thermocouple effects, caused by temperature gradients across dissimilar metals at the contacts to the input LT1028/LT1128 APPLICATI S I FOR ATIO U Frequency Response The LT1028’s Gain, Phase vs Frequency plot indicates that the device is stable in closed-loop gains greater than +2 or –1 because phase margin is about 50° at an open-loop gain of 6dB. In the voltage follower configuration phase margin seems inadequate. This is indeed true when the output is shorted to the inverting input and the noninverting input is driven from a 50Ω source impedance. However, when feedback is through a parallel R-C network (provided CF < 68pF), the LT1028 will be stable because of interaction between the input resistance and capacitance and the feedback network. Larger source resistance at the noninverting input has a similar effect. The following voltage follower configurations are stable: 33pF 2k 1028/1128 AI08 terminals, can exceed the inherent drift of the amplifier unless proper care is exercised. Air currents should be minimized, package leads should be short, the two input leads should be close together and maintained at the same temperature. The circuit shown to measure offset voltage is also used as the burn-in configuration for the LT1028/LT1128. Test Circuit for Offset Voltage and Offset Voltage Drift with Temperature 10k* 15V 2 200Ω* 3 10k* – + 7 6 VO LT1028 LT1128 4 –15V VO = 100VOS * RESISTORS MUST HAVE LOW THERMOELECTRIC POTENTIAL Unity-Gain Buffer Applications (LT1128 Only) When RF ≤ 100Ω and the input is driven with a fast, largesignal pulse (>1V), the output waveform will look as shown in the pulsed operation diagram. RF – OUTPUT 6V/µs 1028/1128 AI07 + During the fast feedthrough-like portion of the output, the input protection diodes effectively short the output to the input and a current, limited only by the output short-circuit protection, will be drawn by the signal generator. With RF ≥ 500Ω, the output is capable of handling the current requirements (IL ≤ 20mA at 10V) and the amplifier stays in its active mode and a smooth transition will occur. As with all operational amplifiers when RF > 2k, a pole will be created with RF and the amplifier’s input capacitance, creating additional phase shift and reducing the phase margin. A small capacitor (20pF to 50pF) in parallel with RF will eliminate this problem. W U UO – LT1028 – 500Ω LT1028 + 50Ω + 50Ω 1028/1128 AI09 Another configuration which requires unity-gain stability is shown below. When CF is large enough to effectively short the output to the input at 15MHz, oscillations can occur. The insertion of RS2 ≥ 500Ω will prevent the LT1028 from oscillating. When RS1 ≥ 500Ω, the additional noise contribution due to the presence of RS2 will be minimal. When RS1 ≤ 100Ω, RS2 is not necessary, because RS1 represents a heavy load on the output through the CF short. When 100Ω < RS1 < 500Ω, RS2 should match RS1 . For example, RS1 = RS2 = 300Ω will be stable. The noise increase due to RS2 is 40%. C1 R1 RS1 – LT1028 RS2 + 1028/1128 AI10 13 LT1028/LT1128 APPLICATI S I FOR ATIO U tion has a high (≈ 70%) overshoot without the 10pF capacitor because of additional phase shift caused by the feedback resistor – input capacitance pole. The presence of the 10pF capacitor cancels this pole and reduces overshoot to 5%. Over-Compensation 10k 1.1k If CF is only used to cut noise bandwidth, a similar effect can be achieved using the over-compensation terminal. The Gain, Phase plot also shows that phase margin is about 45° at gain of 10 (20dB). The following configura10pF – LT1028 + 50Ω 1028/1128 AI11 TYPICAL APPLICATIO S Strain Gauge Signal Conditioner with Bridge Excitation 15V 3 5.0V 2 LT1021-5 + – 7 6 330Ω LT1128 4 –15V 350Ω BRIDGE REFERENCE OUTPUT 15V 3 301k* 7 6 1µF 10k ZERO TRIM 15V 3 – + 7 6 330Ω *RN60C FILM RESISTORS LT1028 2 4 –15V THE LT1028’s NOISE CONTRIBUTION IS NEGLIGIBLE COMPARED TO THE BRIDGE NOISE. 14 W 2 U U UO The LT1028/LT1128 are equipped with a frequency overcompensation terminal (Pin 5). A capacitor connected between Pin 5 and the output will reduce noise bandwidth. Details are shown on the Slew Rate, Gain-Bandwidth Product vs Over-Compensation Capacitor plot. An additional benefit is increased capacitive load handling capability. Low Noise Voltage Regulator 28V + 121Ω 2.3k PROVIDES PRE-REG AND CURRENT LIMITING 10 LT317A 10 28V 1k LT1021-10 + LT1028 330Ω 2N6387 – + – 0V TO 10V OUTPUT 30.1k* LT1028 4 –15V 1000pF 2k 20V OUTPUT 5k GAIN TRIM 2k 49.9Ω* 1028/1128 TA04 1028/1128 TA05 LT1028/LT1128 TYPICAL APPLICATIO S Paralleling Amplifiers to Reduce Voltage Noise 10Ω + A1 LT1028 1.5k – 7.5Ω 470Ω 4.7k 100pF + A2 LT1028 1.5k – 7.5Ω 470Ω + An LT1028 1.5k – 7.5Ω 470Ω 1. ASSUME VOLTAGE NOISE OF LT1028 AND 7.5Ω SOURCE RESISTOR = 0.9nV/√Hz. 2. GAIN WITH n LT1028s IN PARALLEL = n × 200. 3. OUTPUT NOISE = √n × 200 × 0.9nV/√Hz. OUTPUT NOISE 0.9 4. INPUT REFERRED NOISE = = nV/√Hz. n × 200 √n 5. NOISE CURRENT AT INPUT INCREASES √n TIMES. 2µV 6. IF n = 5, GAIN = 1000, BANDWIDTH = 1MHz, RMS NOISE, DC TO 1MHz = = 0.9µV. √5 Low Noise, Wide Bandwidth Instrumentation Amplifier –INPUT + LT1028 300Ω 820Ω 68pF – 50Ω 10Ω – LT1028 +INPUT 820Ω 68pF 300Ω + 10k 100Ω 1028/1128 TA09 1028/1128 TA08 GAIN = 1000, BANDWIDTH = 1MHz INPUT REFERRED NOISE = 1.5nV/√Hz AT 1kHz WIDEBAND NOISE –DC to 1MHz = 3µVRMS IF BW LIMITED TO DC TO 100kHz = 0.55µVRMS U Phono Preamplifier 787Ω 15V 2 0.1µF 10k 0.33µF 6 OUTPUT – + 7 LT1028 3 47k 4 –15V ALL RESISTORS METAL FILM – LT1028 OUTPUT + MAG PHONO INPUT 1028/1128 TA06 Tape Head Amplifier 499Ω 0.1µF 31.6k 10Ω 2 – LT1028 6 OUTPUT TAPE HEAD INPUT 3 + 1028/1128 TA07 1028/1128 TA03 ALL RESISTORS METAL FILM Gyro Pick-Off Amplifier 10k GYRO TYPICAL– NORTHROP CORP. GR-F5AH7-5B SINE DRIVE – LT1028 OUTPUT • + LT1028 OUTPUT TO SYNC DEMODULATOR 1k + – 15 LT1028/LT1128 TYPICAL APPLICATIO S Super Low Distortion Variable Sine Wave Oscillator C1 0.047 R1 20Ω 2k C2 0.047 2k R2 2N4338 560Ω 100k LT1055 20k TRIM FOR LOWEST DISTORTION