LT1008 Picoamp Input Current, Microvolt Offset, Low Noise Op Amp DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ Guaranteed Bias Current TA = 25°C: 100pA Max TA = – 55°C to 125°C: 600pA Max Guaranteed Offset Voltage: 120μV Max Guaranteed Drift: 1.5μV/°C Max Low Noise, 0.1Hz to 10Hz: 0.5μVP-P Guaranteed Low Supply Current: 600μA Max Guaranteed CMRR: 114dB Min Guaranteed PSRR: 114dB Min Guaranteed Voltage Gain with 5mA Load Current Available in 8-Lead PDIP and SO Packages U APPLICATIO S ■ ■ ■ ■ ■ ■ ■ Precision Instrumentation Charge Integrators Wide Dynamic Range Logarithmic Amplifiers Light Meters Low Frequency Active Filters Standard Cell Buffers Thermocouple Amplifiers The LT®1008 is a universal precision operational amplifier that can be used in practically all precision applications. The LT1008 combines for the first time, picoampere bias currents (which are maintained over the full – 55°C to 125°C temperature range), microvolt offset voltage (and low drift with time and temperature), low voltage and current noise, and low power dissipation. Extremely high common mode and power supply rejection ratios, and the ability to deliver 5mA load current with high voltage gain round out the LT1008’s superb precision specifications. The all around excellence of the LT1008 eliminates the necessity of the time consuming error analysis procedure of precision system design in many applications; the LT1008 can be stocked as the universal precision op amp. The LT1008 is externally compensated with a single capacitor for additional flexibility in shaping the frequency response of the amplifier. It plugs into and upgrades all standard LM108A/LM308A applications. For an internally compensated version with even lower offset voltage but otherwise similar performance see the LT1012. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO Input Amplifier for 4.5 Digit Voltmeter Input Bias Current vs Temperature 100 2 INPUT 0.1V 1V 100k 5% – 1 15V 7 3 + LT1008 4 9M 6 9k* 1k* 10V 100V 10V 100V –15V 900k 1000V TO 1V FULL-SCALE ANALOG-TO-DIGITAL CONVERTER *RATIO MATCH ±0.01% 90k 1000V 10k 0.1V 1V 8 FN507 ALLEN BRADLEY DECADE VOLTAGE DIVIDER THIS APPLICATION REQUIRES LOW BIAS CURRENT AND OFFSET VOLTAGE, LOW NOISE AND LOW DRIFT WITH TIME AND TEMPERATURE 1008 TA01 INPUT BIAS CURRENT (pA) 1000pF 50 UNDERCANCELLED UNIT 0 OVERCANCELLED UNIT –50 –100 –150 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1008 TA02 1008fb 1 LT1008 W W W AXI U U ABSOLUTE RATI GS (Note 1) Supply Voltage ...................................................... ±20V Differential Input Current (Note 2) ..................... ±10mA Input Voltage ........................................................ ±20V Output Short-Circuit Duration ......................... Indefinite Storage Temperature Range ................. – 65°C to 150°C Operating Temperature Range LT1008M (OBSOLETE) ............... – 55°C to 125°C LT1008C ................................................. 0°C to 70°C LT1008I ............................................. – 40°C to 85°C Lead Temperature (Soldering, 10 sec).................. 300°C U U W PACKAGE/ORDER I FOR ATIO TOP VIEW TOP VIEW COMP2 8 COMP1 1 TOP VIEW 7 V+ – + –IN 2 6 OUT COMP1 1 8 COMP2 –IN 2 7 V+ COMP1 1 8 COMP2 7 V+ +IN 3 6 OUT –IN 2 V– 4 5 NC +IN 3 6 OUT V– 4 5 NC 5 NC +IN 3 4 N8 PACKAGE 8-LEAD PDIP TJMAX = 150°C, θJA = 130°C/W – (CASE) V H PACKAGE 8-LEAD TO-5 METAL CAN TJMAX = 150°C, θJA = 150°C/W, θJC = 45°C/W S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 190°C/W J8 PACKAGE 8-LEAD CERDIP TJMAX = 150°C, θJA = 100°C/W ORDER PART NUMBER ORDER PART NUMBER ORDER PART NUMBER ORDER PART NUMBER S8 PART MARKING LT1008MH LT1008CH LT1008MJ8 LT1008CJ8 LT1008CN8 LT1008IN8 LT1008S8 1008 Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ OBSOLETE PACKAGES Consider N8 or S8 Package for Alternate Source Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER VOS Input Offset Voltage VS = ±15V, VCM = 0V, TA = 25°C, unless otherwise noted. CONDITIONS LT1008M/I MIN TYP MAX 30 40 (Note 3) IOS Long-Term Input Offset Voltage Stability 0.3 Input Offset Current (Note 3) 30 40 (Note 3) Input Noise Voltage MIN 120 180 LT1008C TYP MAX 30 40 120 180 100 150 pA pA ±30 ±100 ±40 ±150 ±30 ±100 ±40 ±150 pA pA 0.1Hz to 10Hz 0.5 0.5 Input Noise Voltage Density fO = 10Hz (Note 4) fO = 1000Hz (Note 5) 17 14 in Input Noise Current Density fO = 10Hz 20 AVOL Large-Signal Voltage Gain VOUT = ±12V, RL ≥ 10k VOUT = ±10V, RL ≥ 2k IB en Input Bias Current 200 120 2000 600 30 40 μV μV μV/Month 0.3 100 150 UNITS 30 22 17 14 200 120 μVP-P 30 22 nV√Hz nV/√Hz 20 fA/√Hz 2000 600 V/mV V/mV 1008fb 2 LT1008 ELECTRICAL CHARACTERISTICS VS = ±15V, VCM = 0V, TA = 25°C, unless otherwise noted. LT1008M/I MIN TYP MAX PARAMETER CONDITIONS CMRR Common Mode Rejection Ratio VCM = ±13.5V 114 132 114 132 dB PSRR Power Supply Rejection Ratio VS = ±2V to ±20V 114 132 114 132 dB ±13.5 ±14 V ±13.5 ±14 Input Voltage Range VOUT IS MIN LT1008C TYP MAX SYMBOL UNITS Output Voltage Swing RL = 10k ±13 ±14 ±13 ±14 V Slew Rate CF = 30pF 0.1 0.2 0.1 0.2 V/μs Supply Current (Note 3) 380 600 380 600 μA The ● indicates specifications which apply over the full operating temperature range of – 55°C ≤ TA ≤ 125°C for the LT1008M, – 40°C ≤ TA ≤ 85°C for the LT1008I and 0°C ≤ TA ≤ 70°C for the LT1008C. VS = ±15V, VCM = 0V, unless otherwise noted. SYMBOL PARAMETER VOS Input Offset Voltage (Note 3) Average Temperature Coefficient of Input Offset Voltage IOS Input Offset Current (Note 3) Average Temperature Coefficient of Input Offset Current IB LT1008M/I MIN TYP MAX CONDITIONS Input Bias Current (Note 3) Average Temperature Coefficient of Input Bias Current MIN LT1008C TYP MAX UNITS ● ● 50 60 250 320 40 50 180 250 μV μV ● 0.2 1.5 0.2 1.5 μV/°C ● ● 60 80 250 350 40 50 180 250 pA pA ● 0.4 2.5 0.4 2.5 pA/°C ±80 ±600 ±150 ±800 ● ● ● 0.6 ±40 ±180 ±50 ±250 6 0.4 2.5 pA pA pA/°C AVOL Large-Signal Voltage Gain VOUT = ±12V, RL ≥ 10k ● 100 1000 150 1500 CMRR Common Mode Rejection Ratio VCM = ±13.5V ● 108 128 110 130 dB Power Supply Rejection Ratio VS = ±2.5V to ±20V ● 108 126 110 128 dB ● ±13.5 ● ±13 PSRR Input Voltage Range VOUT Output Voltage Swing IS Supply Current RL = 10k ● V/mV ±13.5 ±14 400 ±13 V ±14 V 800 μA TYP MAX UNITS 30 40 200 250 μV μV 800 400 (LT1008S8 only) VS = ±15V, VCM = 0V, TA = 25°C, unless otherwise noted. SYMBOL PARAMETER VOS Input Offset Voltage CONDITIONS (Note 3) Long-Term Input Offset Voltage Stability IOS IB en MIN μV/Month 0.3 Input Offset Current (Note 3) 100 120 280 380 pA pA (Note 3) ±100 ±120 ±300 ±400 pA pA Input Bias Current Input Noise Voltage 0.1Hz to 10Hz 0.5 Input Noise Voltage Density fO = 10Hz (Note 5) fO = 1000Hz (Note 5) 17 14 μVP-P 30 22 nV/√Hz nV/√Hz 1008fb 3 LT1008 ELECTRICAL CHARACTERISTICS (LT1008S8 only) VS = ±15V, VCM = 0V, TA = 25°C, unless otherwise noted. SYMBOL PARAMETER CONDITIONS in Input Noise Current Density fO = 10Hz AVOL Large-Signal Voltage Gain CMRR PSRR MIN TYP 20 fA/√Hz VOUT = ±12V, RL ≥ 10k VOUT = ±10V, RL ≥ 2k 200 120 2000 600 V/mV V/mV Common Mode Rejection Ratio VCM = ±13.5V 110 132 dB Power Supply Rejection Ratio VS = ±2V to ±20V Input Voltage Range VOUT IS MAX UNITS 110 132 dB ±13.5 ±14 V ±14 V Output Voltage Swing RL = 10k ±13 Slew Rate CF = 30pF 0.1 Supply Current (Note 3) 0.2 380 V/μs 600 μA (LT1008S8 only) The ● indicates specifications which apply over the full operating temperature range of 0°C ≤ TA ≤ 70°C. VS = ±15V, VCM = 0V, unless otherwise noted. SYMBOL PARAMETER VOS Input Offset Voltage CONDITIONS MIN (Note 3) Average Temperature Coefficient of Input Offset Voltage IOS Input Offset Current (Note 3) Average Temperature Coefficient of Input Offset Current IB Input Bias Current (Note 3) Average Temperature Coefficient of Input Bias Current TYP MAX UNITS ● ● 40 50 280 340 μV μV ● 0.2 1.8 μV/°C ● ● 120 140 380 500 pA pA ● 0.4 4 ● ● ±120 ±140 ±420 ±550 ● 0.4 5 pA/°C pA pA pA/°C AVOL Large-Signal Voltage Gain VOUT = ±12V, RL ≥ 10k ● 150 1500 V/mV CMRR Common Mode Rejection Ratio VCM = ±13.5V ● 108 130 dB Power Supply Rejection Ratio VS = ±2.5V to ±20V ● 108 128 dB ● ±13.5 ● ±13 PSRR Input Voltage Range VOUT Output Voltage Swing IS Supply Current RL = 10k 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: Differential input voltages greater than 1V will cause excessive current to flow through the input protection diodes unless current limiting resistors are used. ● V ±14 400 V 800 μA Note 3: These specifications apply for ±2V ≤ VS ≤ ±20V (±2.5V ≤ VS ≤ ±20V over the temperature range) and –13.5V ≤ VCM ≤ 13.5V (for VS = ±15V). Note 4: 10Hz noise voltage density is sample tested on every lot. Devices 100% tested at 10Hz are available on request. Note 5: This parameter is tested on a sample basis only. 1008fb 4 LT1008 W FREQUE CY CO PE SATIO CIRCUITS U U U Standard Compensation Circuit R1 Alternate* Frequency Compensation R2 R1 –VIN R2 –VIN 2 R3 +VIN 3 **BANDWIDTH AND SLEW RATE ARE PROPORTIONAL TO 1/CF – + 6 LT1008 VOUT 8 3 +VIN R1CO R1 + R2 CO = 30pF CF ≥ 1 2 *IMPROVES REJECTION OF POWER SUPPLY NOISE BY A FACTOR OF 5 **BANDWIDTH AND SLEW RATE ARE PROPORTIONAL TO 1/CS – + 6 LT1008 VOUT 8 CS** 100pF 1008 FCC02 CF** 1008 FCC01 FOR R2 > 200, NO EXTERNAL FREQUENCY COMPENSATION IS NECESSARY R1 U W Offset Voltage Drift vs Source Resistance (Balanced or Unbalanced) Offset Voltage vs Source Resistance (Balanced or Unbalanced) 10 10 MAXIMUM 1 Input Bias Current vs Common Mode Range 60 VS = ±15V TA = 25°C 1 MAXIMUM 0.1 TYPICAL 10k 100k 1M 10M SOURCE RESISTANCE (Ω) 1k 100M 100k 1M 10M 10k SOURCE RESISTANCE (Ω) 0 100M IB 3 2 METAL CAN (H) PACKAGE 1 DUAL-IN-LINE PACKAGE PLASTIC (N) OR CERDIP (J) 10 –5 0 5 –10 COMMON MODE INPUT VOLTAGE (V) 15 Offset Voltage Drift with Temperature of Four Representative Units 60 8 40 6 OFFSET VOLTAGE (μV) CHANGE IN OFFSET VOLTAGE (μV) 4 VCM – + 1008 G03 10 VS = ±15V TA = 25°C DEVICE WITH NEGATIVE INPUT CURRENT –20 Long-Term Stability of Four Representative Units Warm-Up Drift CHANGE IN OFFSET VOLTAGE (μV) RINCM = 2 × 1012Ω 1008 G02 1008 G01 5 20 –60 –15 0.01 1k DEVICE WITH POSITIVE INPUT CURRENT –40 TYPICAL 0.1 VS = ±15V TA = 25°C 40 INPUT BIAS CURRENT (pA) 100 INPUT OFFSET VOLTAGE (mV) OFFSET VOLTAGE DRIFT WITH TEMPERATURE (μV/°C) TYPICAL PERFOR A CE CHARACTERISTICS 4 2 0 –2 –4 –6 20 0 –20 –40 –8 0 0 1 3 4 2 TIME AFTER POWER ON (MINUTES) 5 1008 G04 –10 0 1 3 2 TIME (MONTHS) 4 5 1008 G05 –60 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 1008 G06 1008fb 5 LT1008 U W TYPICAL PERFOR A CE CHARACTERISTICS Supply Current vs Supply Voltage Output Short-Circuit Current vs Time 15 500 SHORT-CIRCUIT CURRENT (mA) SINKING SOURCING SUPPLY CURRENT (μA) 12 450 400 25°C 125°C 350 –55°C –55°C 9 6 125°C 25°C 3 0 –3 125°C –6 25°C –9 –55°C –12 300 –15 10 15 5 SUPPLY VOLTAGE (±V) 0 0 20 2.5 3.0 3.5 0.5 1.0 1.5 2.0 TIME FROM OUTPUT SHORT (MINUTES) 1008 G08 1008 G07 0.1Hz to 10Hz Noise Noise Spectrum 1000 TA = 25°C VS = ±2V TO ±20V TOTAL NOISE DENSITY (μV/√Hz) NOISE VOLTAGE (400nV/DIV) VOLTAGE NOISE DENSITY (nV/√Hz) CURRENT NOISE DENSITY (fA/√Hz) TA = 25°C VS = ±2V TO ±20V Total Noise vs Source Resistance 10 100 CURRENT NOISE VOLTAGE NOISE 10 1/f CORNER 2.5Hz 1/f CORNER 120Hz 6 4 TIME (SECONDS) 8 10 100 FREQUENCY (Hz) 1 10 1000 Voltage Gain vs Frequency 40 140 30 GAIN (dB) 20 1 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz) 1008 G12 φ CS = 10pF GAIN CS = 100pF 20 φ CS = 100pF 140 10 0 0 0.1 AT 1Hz RESISTOR NOISE ONLY 102 103 104 105 106 107 SOURCE RESISTANCE (Ω) 160 PHASE MARGIN WITH CS = 100pF = 56° TA = 25°C VS = ±15V –10 0.01 0.1 1 FREQUENCY (MHz) 108 180 200 10 1008 G13 30 20 GAIN CF = 3pF 100 φ CF = 30pF 120 φ CF = 3pF GAIN CF = 30pF 140 10 PHASE MARGIN 0 WITH C = 30pF = 60° F TA = 25°C VS = ±15V –10 0.1 1 0.01 FREQUENCY (MHz) 160 PHASE SHIFT (DEG) CS = 10pF CF = 30pF RS = 2R 40 120 100 –20 0.01 0.1 100 PHASE SHIFT (DEG) VOLTAGE GAIN (dB) CF = 3pF 40 – + Gain, Phase Shift vs Frequency with Standard (Feedback) Compensation GAIN CS = 10pF 120 60 R 1008 G11 Gain, Phase Shift vs Frequency with Alternate Compensation CS = 100pF R 1008 G10 1008 G09 80 1 AT 10Hz GAIN (dB) 2 AT 10Hz AT 1Hz 0.01 1 0 TA = 25°C VS = ±2V TO ±20V 180 200 10 1008 G14 1008fb 6 LT1008 U W TYPICAL PERFOR A CE CHARACTERISTICS Common Mode Rejection vs Frequency 10M 140 –55°C 3M VOLTAGE GAIN COMMON MODE REJECTION RATIO (dB) VS = ±15V VO = ±10V 25°C 1M 125°C 300k Power Supply Rejection vs Frequency VS = ±15V TA = 25°C 120 CF = 30pF 100 CS = 100pF 80 60 40 20 100k 0 1 10 2 5 LOAD RESISTANCE (kΩ) 1 20 10k 1k 100 FREQUENCY (Hz) 10 100k 1008 G15 VS = ±15V TA = 25°C 120 NEGATIVE SUPPLY 100 POSITIVE SUPPLY CF = 30pF 80 POSITIVE SUPPLY CS = 100pF 60 40 20 0.1 1 10 100 1k 10k FREQUENCY (Hz) 1008 G16 1M Large-Signal Transient Response VS = ±15V TA = 25°C 2V/DIV SLEW RATE (V/μs) 10 100k 1008 G17 Slew Rate vs Compensation Capacitance Large-Signal Transient Response 2V/DIV 1M 140 POWER SUPPLY REJECTION RATIO (dB) Voltage Gain vs Load Resistance 1 CS CF AV = 1 CS = 100pF 20μs/DIV AV = 1 CF = 30pF 1008 G18 0.1 0 20 40 60 80 COMPENSATION CAPACITOR (pF) 20μs/DIV 1008 G20 100 108 G19 AV = 1 CS = 100pF CLOAD = 100pF 5μs/DIV 1008 G21 Small-Signal Transient Response 20mV/DIV Small-Signal Transient Response 20mV/DIV 20mV/DIV Small-Signal Transient Response AV = 1 CS = 100pF CLOAD = 600pF 5μs/DIV 1008 G22 AV = 1 CF = 30pF CLOAD = 100pF 5μs/DIV 1008 G23 1008fb 7 LT1008 U W U U APPLICATIO S I FOR ATIO Achieving Picoampere/Microvolt Performance In order to realize the picoampere—microvolt level accuracy of the LT1008, proper care must be exercised. For example, leakage currents in circuitry external to the op amp can significantly degrade performance. High quality insulation should be used (e.g., TeflonTM, Kel-F); cleaning of all insulating surfaces to remove fluxes and other residues will probably be required. Surface coating may be necessary to provide a moisture barrier in high humidity environments. The LT1008 is specified over a wide range of power supply voltages from ±2V to ±18V. Operation with lower supplies is possible down to ±1.2V (two Ni-Cad batteries). Test Circuit for Offset Voltage and Its Drift with Temperature 50k* 15V 2 100Ω* 3 – + *RESISTORS MUST HAVE LOW THERMOELECTRIC POTENTIAL 7 LT1008 6 VO 4 Board leakage can be minimized by encircling the input circuitry with a guard ring operated at a potential close to that of the inputs: in inverting configurations the guard ring should be tied to ground, in noninverting connections to the inverting input at Pin 2. Guarding both sides of the printed circuit board is required. Bulk leakage reduction depends on the guard ring width. Nanoampere level leakage into the compensation terminals can affect offset voltage and drift with temperature. COMPENSATION V+ 7 OUTPUT 1 6 2 4 3 1008 AI02 Noise Testing The 0.1Hz to 10Hz peak-to-peak noise of the LT1008 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. PU TS Current noise is measured in the circuit shown and calculated by the following formula where the noise of the source resistors is subtracted. IN V– VO = 1000VOS –15V A noise voltage density test is recommended when measuring noise on a large number of units. A 10Hz noise voltage 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. 8 5 50k* THIS CIRCUIT IS ALSO USED AS THE BURN-IN CONFIGURATION FOR THE LT1008 WITH SUPPLY VOLTAGES INCREASED TO ±20V GUARD 1008 AI01 REFERENCE ONLY—OBSOLETE PACKAGE Microvolt level error voltages can also be generated in the external circuitry. Thermocouple effects caused by temperature gradients across dissimilar metals at the contacts to the input terminals can exceed the inherent drift of the amplifier. Air currents over device leads should be minimized, package leads should be short, and the two input leads should be as close together as possible and maintained at the same temperature. 1/ 2 ⎡e2no – (820nV )2 ⎤ ⎢ ⎦⎥ in = ⎣ 40MΩ × 100 10k 10M* 10M* 2 100Ω 10M* 10M* 3 *METAL FILM – LT1008 6 eno + 1008 AI04 1008fb 8 LT1008 U W U U APPLICATIO S I FOR ATIO 0.1Hz to 10Hz Noise Test Circuit 0.1μF 100k 10Ω – 2k + + LT1008* 4.7μF 22μF 4.3k LT1001 VOLTAGE GAIN: 50,000 110k 2.2μF – SCOPE ×1 RIN = 1M 100k 24.3k Frequency Compensation The LT1008 is externally frequency compensated with a single capacitor. The two standard compensation circuits shown earlier are identical to the LM108A/LM308A frequency compensation schemes. Therefore, the LT1008 operational amplifiers can be inserted directly into LM108A/LM308A sockets, with similar AC and upgraded DC performance. External frequency compensation provides the user with additional flexibility in shaping the frequency response of the amplifier. For example, for a voltage gain of ten and CF = 3pF, a gain bandwidth product of 5MHz and slew rate of 1.2V/μs can be realized. For closed-loop gains in excess of 200, no external compensation is necessary, and slew rate increases to 4V/μs. The LT1008 can also be overcompensated (i.e., CF > 30pF or CS > 100pF) to improve capacitive load handling capability or to narrow noise bandwidth. In many applications, the feedback loop around the amplifier has gain (e.g., logarithmic amplifiers); overcompensation can stabilize these circuits with a single capacitor. The availability of the compensation terminals permits the use of feedforward frequency compensation to enhance slew rate in low closed-loop gain configurations. The inverter slew rate is increased to 1.4V/μs. The voltage follower feedforward scheme bypasses the amplifier’s gain stages and slews at nearly 10V/μs. The inputs of the LT1008 are protected with back-to-back diodes. Current limiting resistors are not used, because the leakage of these resistors would prevent the realization of picoampere level bias currents at elevated temperatures. 0.1μF 1008 AI03 In the voltage follower configuration, when the input is driven by a fast, large-signal pulse (>1V), the input protection diodes effectively short the output to the input during slewing, and a current, limited only by the output shortcircuit protection, will flow through the diodes. The use of a feedback resistor, as shown in the voltage follower feedforward diagram, is recommended because this resistor keeps the current below the short-circuit limit, resulting in faster recovery and settling of the output. Inverter Feedforward Compensation C2 5pF R1 10k INPUT 2 R2 10k – 6 LT1008 3 1 C1 500pF VOUT 8 + R3 3k C3 10pF 1008 AI05 2V/DIV *DEVICE UNDER TEST NOTE: ALL CAPACITOR VALUES ARE FOR NONPOLARIZED CAPACITORS ONLY 5μs/DIV 1008 AI07 1008fb 9 LT1008 U W U U APPLICATIO S I FOR ATIO Follower Feedforward Compensation 30pF 10k 10k INPUT* – 6 LT1008 3 + 5V/DIV 2 OUTPUT 8 1000pF 1008 AI06 *SOURCE RESISTANCE ≤15k FOR STABILITY 5μs/DIV 1008 AI07 U TYPICAL APPLICATIO S Logarithmic Amplifier Q1A 2N2979 Q1B 2N2979 124k* 5.1k 15V 15V 7 – 8 1 2 LM107 1k TEL. LABS TYPE Q81 4 + 100pF 6 15.7k 6 LT1008 3 2k 330pF + 2 – 10k* INPUT LT1004C 1.2V 3 –15V OUTPUT *1% FILM RESISTOR 30pF LOW BIAS CURRENT AND OFFSET VOLTAGE OF THE LT1008 ALLOW 4.5 DECADES OF VOLTAGE INPUT LOGGING Amplifier for Bridge Transducers R1 100k R2 100k 3 C1 30pF R3 510k R6 56M 1 2 – 8 LT1008 3 + 6 OUTPUT + VOLTAGE GAIN ≈ 100 1008 TA04 7 + 2N3609 6 LT1008 2 R4 510k S2 T 100k 15V R5 56M V+ S1 T 100k Saturated Standard Cell Amplifier 1.018235V SATURATED STANDARD CELL #101 EPPLEY LABS NEWPORT, R.I. OUTPUT 4 – 8 1 1000pF –15V R2 R1 1008 TA05 THE TYPICAL 30pA BIAS CURRENT OF THE LT1008 WILL DEGRADE THE STANDARD CELL BY ONLY 1ppm/YEAR. NOISE IS A FRACTION OF A ppm. UNPROTECTED GATE MOSFET ISOLATES STANDARD CELL ON POWER DOWN 1008fb 10 LT1008 U TYPICAL APPLICATIO S Amplifier for Photodiode Sensor Five Decade Kelvin-Varley Divider Buffered by the LT1008 R1 5M 1% 2 10V LT1008 3 100k KELVIN-VARLEY DIVIDER ESI #DP311 00000 – 99999 + 1 – S1 λ R2 5M 1% 15V + 2 8 6 C1 100pF OUTPUT 7 – 6 LT1008 3 OUTPUT 4 + 8 1 –15V VOUT = 10V/μA 1000pF 1008 TA06 APPROXIMATE ERROR DUE TO NOISE, BIAS CURRENT, COMMON MODE REJECTION. VOLTAGE GAIN OF THE 1008 TA07 AMPLIFIER IS 1/5 OF A LEAST SIGNIFICANT BIT The LT1008 integrator extends low frequency range. Total dynamic range is 0.01Hz to 10kHz (or 120dB) with 0.01% linearity. Extended Range Charge Pump Voltage to Frequency Converter 15V 50k –15V 15V OPTIONAL 0.01Hz TRIM 1000pF (POLYSTYRENE) 1.8k 22M 1μF 2 – 63.4k* 6 10k* 3 + 100pF 100k 750k 10k* 2 – LT1008 3 + 8 LM301A 1k 6 LM329 22k 10k 7 15V 2 LT1004C 1.2V LT311A – 10k* + VIN 0V TO 10V 1 3 10k 10k –15V 15V 4 5pF –15V *1% METAL FILM RESISTOR ALL DIODES 1N4148 1008 TA08 FREQUENCY OUPUT 0.01Hz TO 10kHz 1008fb 11 LT1008 U TYPICAL APPLICATIO S Precision, Fast Settling, Lowpass Filter This circuit is useful where fast signal acquisition and high precision are required, as in electronic scales. 10k 2 6 LT1008 2k 3 INPUT 1k + 1 OPTO-MOS* 15V 8 1000pF + #1 LT311A 15V – 4 –15V The circuit settles to a final value three times as fast as a simple 1.5M-1μF filter with almost no DC error. 2 3 1 FILTER CUT IN ADJUST 100Ω *OPTO-MOS SWITCH TYPE OFM1A THETA-J CORP 10k 5 15V – 8 7 #2 LT311A + 4 –15V OUTPUT 8 1μF 7 The filter’s time constant is set by the 2k resistor and the 1μF capacitor until comparator 1 switches. The time constant is then set by the 1.5M resistor and the 1μF capacitor. Comparator 2 provides a quick reset. – 1.5M 3 2 1 1008 TA09 Fast Precision Inverters 2pF TO 8pF 10k* 10k* INPUT 10k 1N4148 ×2 10k* 2N4393 ×2 10k* INPUT 15V 1 2 300pF 5 – 7 6 LT318A 3 10pF + 2 15V 2 4 15k 3 10k 1N4148 (4) – 7 – 6 3 4 + 8 1 7 LT318A LT1008 –15V 15V 1000pF OUTPUT + 6 OUTPUT 4 –15V –15V 10k 30pF FULL POWER BANDWIDTH = 2MHz SLEW RATE AT 50V/μs SETTLING (10V STEP) = 12μs TO 0.01% BIAS CURRENT DC = 30pA OFFSET DRIFT = 0.3μV/°C OFFSET VOLTAGE = 30μV *1% METAL FILM 300pF 15V 10k 2 7 – 6 LT1008 3 10k 4 + 8 1 30pF –15V SLEW RATE = 100V/μs SETTLING (10V STEP) = 5μs TO 0.01% OFFSET VOLTAGE = 30μV BIAS CURRENT DC = 30pA *1% METAL FILM 1008 TA10 1008fb 12 LT1008 W W SCHE ATIC DIAGRA COMP1 COMP2 1 8 V+ 7 1.3k Q7 Q20 Q14 22k 22k 4.2k 3k Q22 Q8 1.5k Q6 Q5 Q27 Q4 Q24 Q3 S S 70Ω Q28 S Q2 50k Q15 Q38 Q26 J1 Q31 Q39 3k 1.5k Q12 Q10 6 Q11 Q23 Q9 +INPUT 60Ω OUTPUT 3k Q13 Q1 Q37 S Q16 2 Q43 Q25 Q21 –INPUT Q30 Q29 Q32 3 Q42 Q33 16k Q17 Q18 Q35 Q19 Q40 20k 3.3k Q41 3.3k Q34 V– 4.3k 4.8k 3.3k 320Ω 40Ω 330Ω 4 1008fb 13 LT1008 U PACKAGE DESCRIPTIO H Package 8-Lead TO-5 Metal Can (.200 Inch PCD) (Reference LTC DWG # 05-08-1320) 0.335 – 0.370 (8.509 – 9.398) DIA 0.305 – 0.335 (7.747 – 8.509) 0.027 – 0.045 (0.686 – 1.143) 45°TYP 0.040 (1.016) MAX 0.050 (1.270) MAX SEATING PLANE 0.165 – 0.185 (4.191 – 4.699) GAUGE PLANE 0.010 – 0.045* (0.254 – 1.143) PIN 1 0.028 – 0.034 (0.711 – 0.864) 0.200 (5.080) TYP REFERENCE PLANE 0.500 – 0.750 (12.700 – 19.050) H8(TO-5) 0.200 PCD 1197 0.110 – 0.160 (2.794 – 4.064) INSULATING STANDOFF 0.016 – 0.021** (0.406 – 0.533) *LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE AND 0.045" BELOW THE REFERENCE PLANE 0.016 – 0.024 **FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS (0.406 – 0.610) J8 Package 8-Lead CERDIP (Narrow .300 Inch, Hermetic) (Reference LTC DWG # 05-08-1110) CORNER LEADS OPTION (4 PLCS) 0.023 – 0.045 (0.584 – 1.143) HALF LEAD OPTION 0.045 – 0.068 (1.143 – 1.727) FULL LEAD OPTION 0.005 (0.127) MIN 0.405 (10.287) MAX 8 7 6 5 0.025 (0.635) RAD TYP 0.220 – 0.310 (5.588 – 7.874) 1 2 0.300 BSC (0.762 BSC) 3 4 0.200 (5.080) MAX 0.015 – 0.060 (0.381 – 1.524) 0.008 – 0.018 (0.203 – 0.457) 0° – 15° NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS 0.045 – 0.065 (1.143 – 1.651) 0.014 – 0.026 (0.360 – 0.660) 0.100 (2.54) BSC 0.125 3.175 MIN J8 1298 OBSOLETE PACKAGES 1008fb 14 LT1008 U PACKAGE DESCRIPTIO N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .400* (10.160) MAX 8 7 6 5 1 2 3 4 .255 ± .015* (6.477 ± 0.381) .300 – .325 (7.620 – 8.255) .065 (1.651) TYP .008 – .015 (0.203 – 0.381) ( +.035 .325 –.015 8.255 +0.889 –0.381 .130 ± .005 (3.302 ± 0.127) .045 – .065 (1.143 – 1.651) ) .120 .020 (3.048) MIN (0.508) MIN .018 ± .003 .100 (2.54) BSC (0.457 ± 0.076) N8 1002 NOTE: 1. DIMENSIONS ARE INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 8 .245 MIN 7 6 5 .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .030 ±.005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN .053 – .069 (1.346 – 1.752) .014 – .019 (0.355 – 0.483) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 2 3 4 .004 – .010 (0.101 – 0.254) .050 (1.270) BSC SO8 0303 1008fb 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. 15 LT1008 U TYPICAL APPLICATIO Ammeter measures currents from 100pA to 100μA without the use of expensive high value resistors. Accuracy at 100μA is limited by the offset voltage between Q1 and Q2 and at 100pA by the inverting bias current of the LT1008. Ammeter with Six Decade Range 10k 15V Q3 100μA METER R1 2k 1.2k 100pA Q1 15V CURRENT INPUT 10k 2 RANGE 1nA 7 – Q2 6 LT1008 3 33k 549Ω 4 + 10nA Q4 8 1 549Ω –15V PIN 13 CA3146 LT1004C-1.2 549Ω 100nA 549Ω 0.01μF Q1 TO Q4: RCA CA3146 TRANSISTOR ARRAY CALIBRATION: ADJUST R1 FOR FULL SCALE DEFLECTION WITH 1μA INPUT CURRENT 1μA 549Ω 10μA 549Ω 100μA 1008 TA11 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1012 Picoamp Input Current, Microvolt Offset, Low Noise Op Amp Internally Compensated LT1008 LT1112 Dual Low Power, Precision, Picoamp Input Op Amp Dual LT1012 LT1880 SOT-23, Rail-to-Rail Output, Picoamp Input Current Precision Op Amp Single SOT-23 Version of LT1884 LT1881/LT1882 Dual and Quad Rail-to-Rail Output, Picoamp Input Precision Op Amps Dual/Quad CLOAD Stable LT1884/LT1885 Dual and Quad Rail-to-Rail Output, Picoamp Input Precision Op Amps Dual/Quad Faster LT1881/LT1882 1008fb 16 Linear Technology Corporation LT 0607 REV B • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1991