LTC1151 Dual ±15V Zero-Drift Operational Amplifier U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Maximum Offset Voltage Drift: 0.05µV/°C High Voltage Operation: ±18V No External Components Required Maximum Offset Voltage: 5µV Low Noise: 1.5µVP-P (0.1Hz to 10Hz) Minimum Voltage Gain: 125dB Minimum CMRR: 106dB Minimum PSRR: 110dB Low Supply Current: 0.9mA/Amplifier Single Supply Operation: 4.75V to 36V Input Common-Mode Range Includes Ground Typical Overload Recovery Time: 20ms The LTC1151 is a high voltage, high performance dual zero-drift operational amplifier. The two sample-and-hold capacitors per amplifier required externally by other chopper amplifiers are integrated on-chip. The LTC1151 also incorporates proprietary high voltage CMOS structures which allow operation at up to 36V total supply voltage. The LTC1151 has a typical offset voltage of 0.5µV, drift of 0.01µV/°C, 0.1Hz to 10Hz input noise voltage of 1.5µVP-P, and a typical voltage gain of 140dB. It has a slew rate of 3V/µs and a gain-bandwidth product of 2.5MHz with a supply current of 0.9mA per amplifier. Overload recovery times from positive and negative saturation are 3ms and 20ms, respectively. UO APPLICATI ■ ■ ■ ■ ■ The LTC1151 is available in a standard 8-lead plastic DIP package as well as a 16-lead wide body SO. The LTC1151 is pin compatible with industry-standard dual op amps and runs from standard ±15V supplies, allowing it to plug in to most standard bipolar op amp sockets while offering significant improvement in DC performance. Strain Gauge Amplifiers Instrumentation Amplifiers Electronic Scales Medical Instrumentation Thermocouple Amplifiers High Resolution Data Acquisition UO ■ S TYPICAL APPLICATI ±15V Dual Thermocouple Amplifier 51Ω 100Ω* 240k Noise Spectrum 15V 60 – VIN K 7 + LT1025 3 VO GND 4 R– 5 2k 5 – 8 1/2 LTC1151 7 OUTPUT A 100mV/°C + 240k 51Ω 100Ω* TYPE K 470k 2 + 40 30 20 10 –15V – NOISE VOLTAGE (nV/√Hz) 6 15V 50 0.1µF 0.1µF 2k 3 1/2 LTC1151 + 0 0.1µF – OUTPUT B 100mV/°C 1 1 10 100 1k FREQUENCY (Hz) 10k 1151 TA02 4 0.1µF TYPE K * FULL SCALE TRIM: TRIM FOR 10.0V OUTPUT WITH THERMOCOUPLE AT 100°C –15V 1151 TA01 1 LTC1151 W W W AXI U U ABSOLUTE RATI GS (Note 1) Total Supply Voltage (V + to V –) ............................. 36V Input Voltage (Note 2) .......... (V + + 0.3V) to (V – – 0.3V) Output Short Circuit Duration ......................... Indefinite Burn-In Voltage ...................................................... 36V Operating Temperature Range LTC1151C............................................... 0°C to 70°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C U W U PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW OUT A 1 8 V+ –IN A 2 7 OUT B +IN A 3 6 –IN B V– 4 5 +IN B LTC1151CN8 ORDER PART NUMBER TOP VIEW NC 1 16 NC NC 2 15 NC OUT A 3 14 V+ –IN A 4 13 OUT B +IN A 5 12 –IN B V– 6 11 +IN B NC 7 10 NC NC 8 9 NC N8 PACKAGE 8-LEAD PLASTIC DIP LTC1151CS S PACKAGE 16-LEAD PLASTIC SOL TJMAX = 110°C, θJA = 130°C/ W TJMAX = 110°C, θJA = 200°C/ W ELECTRICAL CHARACTERISTICS VS = ±15V, TA = Operating Temperature Range, unless otherwise specified. PARAMETER CONDITIONS Input Offset Voltage TA = 25°C (Note 3) Average Input Offset Drift (Note 3) MIN ● Long Term Offset Voltage Drift Input Offset Current LTC1151C TYP MAX ±0.5 ±5 ±0.01 ±0.05 50 TA = 25°C TA = 25°C µV µV/°C nV/√mo ±20 ±200 ±0.5 pA nA ±15 ±100 ±0.5 pA nA ● Input Bias Current UNITS ● Input Noise Voltage RS = 100Ω, 0.1Hz to 10Hz RS = 100Ω, 0.1Hz to 1Hz 1.5 0.5 µVP-P µVP-P Input Noise Current f = 10Hz (Note 4) 2.2 fA/√Hz Input Voltage Range Positive Negative ● ● 12 –15 13.2 –15.3 V V Common-Mode Rejection Ratio VCM = V – to 12V ● 106 130 dB Power Supply Rejection Ratio VS = ±2.375V to ±16V ● 110 130 dB Large-Signal Voltage Gain RL = 10k, VOUT = ±10V ● 125 140 dB 2 LTC1151 ELECTRICAL CHARACTERISTICS VS = ±15V, TA = Operating Temperature Range, unless otherwise specified. PARAMETER CONDITIONS Maximum Output Voltage Swing RL = 10k, TA = 25°C RL = 10k RL = 100k Slew Rate MIN ● RL = 10k, CL = 50pF No Load, TA = 25°C No Load MAX UNITS ±13.5 ±14.50 +10.5/–13.5 ±14.95 Gain-Bandwidth Product Supply Current per Amplifier LTC1151C TYP 2.5 V/µs 2 MHz 0.9 ● Internal Sampling Frequency V V V 1.5 2.0 mA mA 1000 Hz VS = 5V, TA = Operating Temperature Range, unless otherwise specified. Input Offset Voltage TA = 25°C (Note 3) Average Input Offset Drift (Note 3) ● Long Term Offset Voltage Drift Input Offset Current ±0.05 ±5 ±0.01 ±0.05 50 TA = 25°C µV µV/°C nV/√mo ±10 100 50 pA Input Bias Current TA = 25°C ±5 Input Noise Voltage RS = 100Ω, 0.1Hz to 10Hz RS = 100Ω, 0.1Hz to 1Hz 2.0 0.7 µVP-P µVP-P Input Noise Current f = 10Hz (Note 4) 1.3 fA/√Hz Input Voltage Range Positive Negative 2.7 0 3.2 – 0.3 V V Common-Mode Rejection Ratio VCM = 0V to 2.7V 110 Power Supply Rejection Ratio VS = ±2.375V to ±16V ● 110 130 dB Large-Signal Voltage Gain RL = 10k, VOUT = 0.3V to 4.5V ● 115 140 dB Maximum Output Voltage Swing RL = 10k to GND RL = 100k to GND 4.85 4.97 V V Slew Rate RL = 10k, CL = 50pF 1.5 V/µs 1.5 MHz Gain Bandwidth Product Supply Current per Amplifier No Load, TA = 25°C dB 0.5 ● Internal Sampling Frequency The • denotes the specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which life of the device may be impaired. Note 2: Connecting any terminal to voltages greater than V + or less than V – may cause destructive latch-up. It is recommended that no sources operating from external supplies be applied prior to power-up of the LTC1151. pA 1.0 1.5 750 mA mA Hz Note 3: These parameters are guaranteed by design. Thermocouple effects preclude measurement of these voltage levels in high speed automatic test systems. VOS is measured to a limit determined by test equipment capability. Note 4: Current Noise is calculated from the formula: IN = √(2q • Ib) where q = 1.6 × 10 –19 Coulomb. 3 LTC1151 U W TYPICAL PERFOR A CE CHARACTERISTICS Supply Current vs Supply Voltage 2.5 15 2.00 VS = ±15V 2.0 1.5 1.0 0.5 0 4 8 12 16 20 24 28 32 TOTAL SUPPLY VOLTAGE (V) TA = 25°C 10 COMMON-MODE RANGE (V) TOTAL SUPPLY CURRENT (mA) TOTAL SUPPLY CURRENT (mA) TA = 25°C 1.75 1.50 10 0 20 30 60 40 50 TEMPERATURE (˚C) 0 70 –3 VOUT = V + ISINK 120 20 15 10 –15 VS = ±15V RL = 10k 80 60 20 0 0 100 12 16 20 24 28 32 36 8 TOTAL SUPPLY VOLTAGE, V + TO V – (V) 100 40 5 –12 VS = ±15V 140 CMRR (dB) OUTPUT VOLTAGE (VP-P) VOUT = V – ISOURCE 4 ±10.0 ±12.5 ±15.0 CMRR vs Frequency 25 –9 ±7.5 160 TA = 25°C –6 ±5.0 1151 G03 30 0 ±2.5 SUPPLY VOLTAGE (V) Undistorted Output Swing vs Frequency 6 2 –5 1151 G02 Output Short-Circuit Current vs Supply Voltage 4 0 –15 1.25 36 5 –10 1151 G01 SHORT-CIRCUIT OUTPUT CURRENT (mA) Common-Mode Input Voltage Range vs Supply Voltage Supply Current vs Temperature 1k 10k 100k FREQUENCY (Hz) 1M 1 10 100 1k FREQUENCY (Hz) 10k 1151 G05 1151 G04 Gain and Phase vs Frequency 100k 1151 G06 PSRR vs Frequency Gain and Phase vs Frequency 160 135 80 PHASE 45 40 0 60 GAIN 45 40 0 20 20 100 80 NEGATIVE SUPPLY 60 40 –45 –45 20 0 0 POSITIVE SUPPLY 120 90 PHASE (DEG) GAIN PHASE (DEG) 60 VS = ±15V 140 135 PHASE 90 GAIN (dB) 80 GAIN (dB) VS = ±2.5V CL = 100pF 100 PSRR (dB) VS = ±15V CL = 100pF 100 0 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M 1151 G07 4 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M 1151 G08 1 10 100 1k FREQUENCY (Hz) 10k 100k 1151 G09 LTC1151 U W TYPICAL PERFOR A CE CHARACTERISTICS Input Bias Current Magnitude vs Supply Voltage Input Bias Current Magnitude vs Temperature 18 1000 VCM = 0 VS = ±15V 60 TA = 25°C VCM = 0V 100 10 12 9 6 3 1 –50 25 50 75 0 TEMPERATURE (°C) 0 100 125 30 –IB 15 0 –15 +IB –30 –45 0 –25 VS = 15V TA = 25°C 45 INPUT BIAS CURRENT (pA) INPUT BIAS CURRENT (pA) 15 ±2 ±4 ±6 ±8 ±10 ±12 ±14 ±16 SUPPLY VOLTAGE (V) –60 –15 –5 5 10 –10 0 INPUT COMMON-MODE VOLTAGE (V) 1151 G11 1151 G10 15 1151 G12 0.1Hz to 10Hz Noise VS = ±15V TA = 25°C 1µV 10s 1s 1151 G13 Large-Signal Transient Response Negative Overload Recovery 5V/DIV Small-Signal Transient Response 5 0 2V/DIV 50mV/DIV 0 2V/DIV INPUT BIAS CURRENT (pA) Input Bias Current vs Input Common-Mode Voltage 2ms/DIV VS = ±15V, AV = 1 CL = 100pF, RL = 10k 1151 G14 VS = ±15V, AV = 1 CL = 100pF, RL = 10k 2ms/DIV 1151 G15 2ms/DIV VS = ±15V, AV = –100 NOTE: POSITIVE OVERLOAD RECOVERY IS TYPICALLY 3ms. 1151 G16 5 LTC1151 TEST CIRCUITS Offset Voltage Test Circuit DC-10Hz Noise Test Circuit 100pF 1M 100k 1k 2 – V+ 7 2 6 LTC1151 3 OUTPUT 10Ω 7 – LTC1151 + 5V 5V RL 4 3 + 2 6 4 V– –5V 1151 TC01 800k 0.02µF 3 – 8 1/2 LT1057 +4 –5V 0.04µF 6 800k 5 – 1/2 LT1057 1 800k 7 OUTPUT + 0.01µF 1151 TC02 U W U UO APPLICATI S I FOR ATIO ACHIEVING PICOAMPERE/MICROVOLT PERFORMANCE Picoamperes In order to realize the picoampere level of accuracy of the LTC1151 proper care must be exercised. Leakage currents in circuitry external to the amplifier can significantly degrade performance. High quality insulation should be used (e.g., Teflon); cleaning of all insulating surfaces to remove fluxes and other residues will probably be necessary, particularly for high temperature performance. Surface coating may be necessary to provide a moisture barrier in high humidity environments. Board leakage can be minimized by encircling the input connections 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. Guarding both sides of the printed circuit board is required. Bulk leakage reduction depends on the guard ring width. Microvolts Thermocouple effects must be considered if the LTC1151’s ultra low drift is to be fully utilized. Any connection of dissimilar metals forms a thermoelectric junction producing an electric potential which varies with temperature (Seebeck effect). As temperature sensors, thermocouples exploit this phenomenon to produce useful information. In low drift amplifier circuits the effect is a primary source of error. 6 Connectors, switches, relay contacts, sockets, resistors, solder, and even copper wire are all candidates for thermal EMF generation. Junctions of copper wire from different manufacturers can generate thermal EMFs of 200nV/°C; four times the maximum drift specification of the LTC1151. Minimizing thermal EMF-induced errors is possible if judicious attention is given to circuit board layout and component selection. It is good practice to minimize the number of junctions in the amplifier’s input signal path. Avoid connectors, sockets, switches, and relays where possible. In instances where this is not possible, attempt to balance the number and type of junctions so that differential cancellation occurs. Doing this may involve deliberately introducing junctions to offset unavoidable junctions. Figure 1 is an example of the introduction of an unnecessary resistor to promote differential thermal balance. Maintaining compensating junctions in close physical proximity will keep them at the same temperature and reduce thermal EMF errors. When connectors, switches, relays and/or sockets are necessary they should be selected for low thermal EMF activity. The same techniques of thermally balancing and coupling the matching junctions are effective in reducing the thermal EMF errors of these components. LTC1151 W U U UO APPLICATI S I FOR ATIO NOMINALLY UNNECESSARY RESISTOR USED TO THERMALLY BALANCE OTHER INPUT RESISTOR LEAD WIRE/SOLDER COPPER TRACE JUNCTION PACKAGE-INDUCED OFFSET VOLTAGE Package-induced thermal EMF effects are another important source of errors. They arise at the junctions formed when wire or printed circuit traces contact a package lead. Like all the previously mentioned thermal EMF effects, they are outside the LTC1151’s offset nulling loop and cannot be cancelled. The input offset voltage specification of the LTC1151 is actually set by the package-induced warm-up drift rather than by the circuit itself. The thermal time constant ranges from 0.5 to 3 minutes, depending on package type. + LTC1151 OUTPUT – RESISTOR LEAD, SOLDER, COPPER TRACE JUNCTION 1151 F01 ALIASING Figure 1. Extra Resistors Cancel Thermal EMF Resistors are another source of thermal EMF errors. Table 1 shows the thermal EMF generated for different resistors. The temperature gradient across the resistor is important, not the ambient temperature. There are two junctions formed at each end of the resistor and if these junctions are at the same temperature, their thermal EMFs will cancel each other. The thermal EMF numbers are approximate and vary with resistor value. High values give higher thermal EMF. Table 1. Resistor Thermal EMF RESISTOR TYPE >1mV/°C Carbon Composition ∼450µV/°C Metal Film ∼20µV/°C Wire Wound Evenohm, Manganin ∼2µV/°C For a complete discussion of the correction circuitry and aliasing behavior, please refer to the LTC1051/LTC1053 data sheet. LOW SUPPLY OPERATION The minimum supply for proper operation of the LTC1151 is typically 4.0V (±2.0V). In single supply applications, PSRR is guaranteed down to 4.7V (±2.35V) to ensure proper operation at minimum TTL supply voltage of 4.75V. THERMAL EMF/°C GRADIENT Tin Oxide Like all sampled data systems, the LTC1151 exhibits aliasing behavior at input frequencies near the sampling frequency. The LTC1151 includes a high frequency correction loop which minimizes this effect. As a result, aliasing is not a problem for many applications. UO TYPICAL APPLICATI S High Voltage Instrumentation Amplifier 1k V+ 1M 1M 2 – 8 1/2 LTC1151 –IN 3 0.1µF 1 1k 6 + +IN 5 – 1/2 LTC1151 + 4 7 VOUT GAIN = 1000V/V OUTPUT OFFSET < 5mA 0.1µF V– 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 circuits as described herein will not infringe on existing patent rights. 1151 TA03 7 LTC1151 UO TYPICAL APPLICATI S Bridge Amplifier with Active Common-Mode Suppression 15V 15V 49.9k 350Ω TRIM TO SET BRIDGE OPERATING CURRENT 0.1µF – 1/2 LTC1151 350Ω STRAIN GAUGE – 1/2 LTC1151 VOUT AV = 100 + 499Ω + 0.1µF –15V 1151 TA04 390Ω –15V U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. N8 Package, 8-Lead Plastic DIP 0.300 – 0.320 (7.620 – 8.128) 0.009 – 0.015 (0.229 – 0.381) ( +0.025 0.325 –0.015 8.255 +0.635 –0.381 ) 0.045 – 0.065 (1.143 – 1.651) 0.400 (10.160) MAX 0.130 ± 0.005 (3.302 ± 0.127) 8 7 0.250 ± 0.010 (6.350 ± 0.254) 0.125 (3.175) MIN 0.045 ± 0.015 (1.143 ± 0.381) 0.020 (0.508) MIN 1 2 0.398 – 0.413 (10.109 – 10.490) 16 0.093 – 0.104 (2.362 – 2.642) SEE NOTE 0.016 – 0.050 (0.406 – 1.270) 14 13 12 11 10 9 0.394 – 0.419 (10.007 – 10.643) SEE NOTE 0.050 (1.270) TYP 0.004 – 0.012 (0.102 – 0.305) 0.014 – 0.019 (0.356 – 0.482) TYP NOTE: PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS. 8 15 0.037 – 0.045 (0.940 – 1.143) 0° – 8° TYP 0.009 – 0.013 (0.229 – 0.330) 4 3 0.018 ± 0.003 (0.457 ± 0.076) 0.100 ± 0.010 (2.540 ± 0.254) 0.291 – 0.299 (7.391 – 7.595) 0.010 – 0.029 × 45° (0.254 – 0.737) 5 0.065 (1.651) TYP S Package, 16-Lead SOL 0.005 (0.127) RAD MIN 6 Linear Technology Corporation 1 2 3 4 5 6 7 8 LT/GP 0193 10K REV 0 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1993