Datasheet

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LT1008

1008fb

Picoamp Input Current,

Microvolt Offset,

Low Noise Op Amp

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 ca-

pacitor 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.

■

Guaranteed Bias Current

= 25°C: 100pA Max

= – 55°C to 125°C: 600pA Max

■

Guaranteed Offset Voltage: 120μV Max

■

Guaranteed Drift: 1.5μV/°C Max

■

Low Noise, 0.1Hz to 10Hz: 0.5μV

P-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

■

Precision Instrumentation

■

Charge Integrators

■

Wide Dynamic Range Logarithmic Amplifiers

■

Light Meters

■

Low Frequency Active Filters

■

Standard Cell Buffers

■

Thermocouple Amplifiers

Input Amplifier for 4.5 Digit Voltmeter

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

–

LT1008

1000pF

100k

15V

–15V

0.1V

INPUT

10V

100V

1000V

1008 TA01

TO 1V FULL-SCALE

ANALOG-TO-DIGITAL

CONVERTER

*RATIO MATCH ±0.01%

100V

900k

9k*

0.1V

1k*

1000V

FN507

ALLEN BRADLEY

DECADE VOLTAGE DIVIDER

THIS APPLICATION REQUIRES LOW

BIAS CURRENT AND OFFSET VOLTAGE,

LOW NOISE AND LOW DRIFT WITH

TIME AND TEMPERATURE

90k

10k

TEMPERATURE (°C)

–50

–150

INPUT BIAS CURRENT (pA)

–50

100

1008 TA02

–100

–25

100

125

UNDERCANCELLED UNIT

OVERCANCELLED UNIT

Input Bias Current vs Temperature

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

Summary of content (16 pages)

PAGE 1
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.
PAGE 2
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 ............................
PAGE 3
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.
PAGE 4
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.
PAGE 5
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 NECES
PAGE 6
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.
PAGE 7
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.
PAGE 8
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.
PAGE 9
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.
PAGE 10
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.
PAGE 11
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.
PAGE 12
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.
PAGE 13
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.
PAGE 14
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.
PAGE 15
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.
PAGE 16
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.