OPA277 OPA2277 OPA4277 ® OPA OPA 277 227 OPA 7 4277 OPA 2277 OPA 277 OPA 4277 For most current data sheet and other product information, visit www.burr-brown.com High Precision OPERATIONAL AMPLIFIERS FEATURES DESCRIPTION ● ULTRA LOW OFFSET VOLTAGE: 10µV ● ULTRA LOW DRIFT: ±0.1µV/°C ● HIGH OPEN-LOOP GAIN: 134dB ● HIGH COMMON-MODE REJECTION: 140dB ● HIGH POWER SUPPLY REJECTION: 130dB ● LOW BIAS CURRENT: 1nA max ● WIDE SUPPLY RANGE: ±2V to ±18V ● LOW QUIESCENT CURRENT: 800µA/amp ● SINGLE, DUAL, AND QUAD VERSIONS ● REPLACES OP-07, OP-77, OP-177 The OPA277 series precision op amps replace the industry standard OP-177. They offer improved noise, wider output voltage swing, and are twice as fast with half the quiescent current. Features include ultra low offset voltage and drift, low bias current, high common-mode rejection, and high power supply rejection. Single, dual, and quad versions have identical specifications for maximum design flexibility. OPA277 series op amps operate from ±2V to ±18V supplies with excellent performance. Unlike most op amps which are specified at only one supply voltage, the OPA277 series is specified for real-world applications; a single limit applies over the ±5V to ±15V supply range. High performance is maintained as the amplifiers swing to their specified limits. Because the initial offset voltage (±20µV max) is so low, user adjustment is usually not required. However, the single version (OPA277) provides external trim pins for special applications. OPA277 op amps are easy to use and free from phase inversion and overload problems found in some other op amps. They are stable in unity gain and provide excellent dynamic behavior over a wide range of load conditions. Dual and quad versions feature completely independent circuitry for lowest crosstalk and freedom from interaction, even when overdriven or overloaded. Single (OPA277) and dual (OPA2277) versions are available in 8-pin DIP and SO-8 surface-mount packages. The quad (OPA4277) comes in 14-pin DIP and SO-14 surface-mount packages. All are fully specified from –40°C to +85°C and operate from –55°C to +125°C. APPLICATIONS ● ● ● ● ● ● ● TRANSDUCER AMPLIFIER BRIDGE AMPLIFIER TEMPERATURE MEASUREMENTS STRAIN GAGE AMPLIFIER PRECISION INTEGRATOR BATTERY POWERED INSTRUMENTS TEST EQUIPMENT OPA277 Offset Trim 1 8 Offset Trim –In 2 7 V+ +In 3 6 Output V– 4 5 NC OPA4277 OPA2277 Out A 1 14 Out D –In A 2 13 –In D A 8-Pin DIP, SO-8 Out A –In A 1 2 +In A 3 V– 4 8 A 7 B V+ Out B 6 –In B 5 +In B 8-Pin DIP, SO-8 D +In A 3 12 +In D V+ 4 11 V– +In B 5 10 +In C B C –In B 6 9 –In C Out B 7 8 Out C 14-Pin DIP, SO-14 IInternational Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 © 1997 Burr-Brown Corporation SBOS079 PDS-1413D Printed in U.S.A. March, 1999 SPECIFICATIONS: VS = ±5V to VS = ±15V At TA = +25°C, and RL = 2kΩ, unless otherwise noted. Boldface limits apply over the specified temperature range, –40°C to +85°C. OPA277PA, UA OPA2277PA, UA OPA4277PA, UA OPA277P, U OPA2277P, U PARAMETER CONDITION OFFSET VOLTAGE Input Offset Voltage: OPA277P, U (high grade, single) OPA2277P, U (high grade, dual) All PA, UA Versions MIN VOS Input Offset Voltage Over Temperature OPA277P, U (high grade, single) OPA2277P, U (high grade, dual) All PA, UA Versions TA = –40°C to +85°C TA = –40°C to +85°C TA = –40°C to +85°C Input Offset Voltage Drift dVOS/dT OPA277P, U (high grade, single) OPA2277P, U (high grade, dual) All PA, UA Versions TA = –40°C to +85°C TA = –40°C to +85°C TA = –40°C to +85°C Input Offset Voltage: (all models) vs Time vs Power Supply TA = –40°C to +85°C Channel Separation (dual, quad) INPUT BIAS CURRENT Input Bias Current TA = –40°C to +85°C Input Offset Current TA = –40°C to +85°C MAX ±10 ±10 ±20 ±25 ±0.1 ±0.1 0.2 ±0.3 ±0.5 I OS ±0.5 Input Voltage Noise Density, f = 10Hz en f = 100Hz f = 1kHz f = 10kHz Current Noise Density, f = 1kHz in 0.22 0.035 12 8 8 8 0.2 NOISE Input Voltage Noise, f = 0.1 to 10Hz VCM CMRR INPUT IMPEDANCE Differential Common-Mode OPEN-LOOP GAIN Open-Loop Voltage Gain TA = –40°C to +85°C FREQUENCY RESPONSE Gain-Bandwidth Product GBW Slew Rate SR Settling Time, 0.1% 0.01% Overload Recovery Time Total Harmonic Distortion + Noise THD+N OUTPUT Voltage Output TA = –40°C to +85°C TA = –40°C to +85°C Short-Circuit Current Capacitive Load Drive VCM = (V–) +2V to (V+) –2V VCM = (V–) +2V to (V+) –2V (V–) +2 130 128 VO = (V–)+0.5V to (V+)–1.2V, RL = 10kΩ VO = (V–)+0.5V to (V+)–1.5V, RL = 2kΩ VO = (V–)+0.5V to (V+)–1.5V, RL = 2kΩ 126 126 ±0.15 ✻ ✻ ±0.5 ±0.5 RL = 10kΩ RL = 10kΩ RL = 2kΩ RL = 2kΩ (V–) (V–) (V–) (V–) +0.5 +0.5 +1.5 +1.5 ±1 ✻ ±1 ✻ ±2 ±2 UNITS ±50 µV µV µV ±100 µV µV µV ±1 µV/°C µV/°C µV/°C ±1 ±1 µV/mo µV/V µV/V µV/V ±2.8 ±4 ±2.8 ±4 nA nA nA nA µVp-p µVrms nV/√Hz nV/√Hz nV/√Hz nV/√Hz pA/√Hz ✻ ✻ ✻ ✻ ✻ ✻ ✻ (V+) –2 140 140 134 ✻ 115 115 ✻ ✻ (V+) (V+) (V+) (V+) ±35 See Typical Curve I SC CLOAD MAX ✻ 1 0.8 14 16 3 0.002 VS = ±15V, G = 1, 10V Step VS = ±15V, G = 1, 10V Step VIN • G = VS 1kHz, G = 1, VO = 3.5Vrms VO ±0.15 ±0.25 100 || 3 250 || 3 VCM = (V–) +2V to (V+) –2V AOL TYP(1) ±20 0.1 IB INPUT VOLTAGE RANGE Common-Mode Voltage Range Common-Mode Rejection TA = –40°C to +85°C MIN ±30 ±50 VS = ±2V to ±18V VS = ±2V to ±18V dc PSRR TYP(1) –1.2 –1.2 –1.5 –1.5 ✻ ✻ V dB dB ✻ ✻ MΩ || pF GΩ || pF ✻ ✻ dB dB dB ✻ ✻ ✻ ✻ ✻ ✻ MHz V/µs µs µs µs % ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ V V V V mA The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems. ® OPA277, 2277, 4277 2 SPECIFICATIONS: VS = ±5V to VS = ±15V (CONT) At TA = +25°C, and RL = 2kΩ, unless otherwise noted. Boldface limits apply over the specified temperature range, –40°C to +85°C. OPA277PA, UA OPA2277PA, UA OPA4277PA, UA OPA277P, U OPA2277P, U PARAMETER CONDITION POWER SUPPLY Specified Voltage Range Operating Voltage Range Quiescent Current (per amplifier) TA = –40°C to +85°C MIN ±5 ±2 VS ±790 IO = 0 IO = 0 IQ TEMPERATURE RANGE Specified Range Operating Range Storage Range Thermal Resistance SO-8 Surface-Mount 8-Pin DIP 14-Pin DIP SO-14 Surface-Mount TYP(1) –40 –55 –55 MAX MIN ±15 ±18 ±825 ±900 ✻ ✻ 85 125 125 ✻ ✻ ✻ TYP(1) ✻ θJA ✻ ✻ ✻ ✻ 150 100 80 100 MAX UNITS ✻ ✻ ✻ ✻ V V µA µA ✻ ✻ ✻ °C °C °C °C/W °C/W °C/W °C/W ✻ Specifications same as OPA277P, U. NOTE: (1) VS = ±15V. ABSOLUTE MAXIMUM RATINGS(1) ELECTROSTATIC DISCHARGE SENSITIVITY Supply Voltage .................................................................................... 36V Input Voltage ..................................................... (V–) –0.7V to (V+) +0.7V Output Short-Circuit(2) .............................................................. Continuous Operating Temperature .................................................. –55°C to +125°C Storage Temperature ..................................................... –55°C to +125°C Junction Temperature ...................................................................... 150°C Lead Temperature (soldering, 10s) ................................................. 300°C This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. NOTE: (1) Stresses above these rating may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. (2) Short-circuit to ground, one amplifier per package. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. PACKAGE/ORDERING INFORMATION PRODUCT OFFSET VOLTAGE max, µV OFFSET VOLTAGE DRIFT max, µV/°C PACKAGE PACKAGE DRAWING NUMBER(1) TEMPERATURE RANGE ORDERING NUMBER(2) TRANSPORT MEDIA Single OPA277PA OPA277P OPA277UA " OPA277U " ±50 ±20 ±50 " ±20 " ±1 ±0.15 ±1 " ±0.15 " 8-Pin DIP 8-Pin DIP SO-8 Surface Mount " SO-8 Surface Mount " 006 006 182 " 182 " –40°C to +85°C –40°C to +85°C –40°C to +85°C " –40°C to +85°C " OPA277PA OPA277P OPA277UA OPA277UA/2K5 OPA277U OPA277U/2K5 Rails Rails Rails Tape and Reel Rails Tape and Reel Dual OPA2277PA OPA2277P OPA2277UA " OPA2277U " ±50 ±25 ±50 " ±25 " ±1 ±0.25 ±1 " ±0.25 " 8-Pin DIP 8-Pin DIP SO-8 Surface Mount " SO-8 Surface Mount " 006 006 182 " 182 " –40°C to +85°C –40°C to +85°C –40°C to +85°C " –40°C to +85°C " OPA2277PA OPA2277P OPA2277UA OPA2277UA/2K5 OPA2277U OPA2277U/2K5 Rails Rails Rails Tape and Reel Rails Tape and Reel Quad OPA4277PA OPA4277UA " ±50 ±50 " ±1 ±1 " 14-Pin DIP SO-14 Surface Mount " 010 235 " –40°C to +85°C –40°C to +85°C " OPA4277PA OPA4277UA OPA4277UA/2K5 Rails Rails Tape and Reel NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) Products followed by a slash (/) are only available in Tape and Reel in the quantities indicated (e.g. /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of “OPA277UA/2K5” will get a single 2500 piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to Appendix B of Burr-Brown IC Data Book. ® 3 OPA277, 2277, 4277 TYPICAL PERFORMANCE CURVES At TA = +25°C, VS = ±15V, and RL = 2kΩ, unless otherwise noted. POWER SUPPLY AND COMMON-MODE REJECTION vs FREQUENCY OPEN-LOOP GAIN/PHASE vs FREQUENCY 140 140 0 100 –30 80 –60 φ 60 –90 40 –120 20 –150 0 –180 120 +PSR –PSR PSR, CMR (dB) AOL (dB) 120 CL = 0 CL = 1500pF Phase (°) G 100 80 CMR 60 40 20 0 –20 0.1 1 10 100 1k 10k 100k 1M 0.1 10M 1 10 100 1k 10k 100k 1M Frequency (Hz) Frequency (Hz) INPUT NOISE AND CURRENT NOISE SPECTRAL DENSITY vs FREQUENCY INPUT NOISE VOLTAGE vs TIME Noise signal is bandwidth limited to lie between 0.1Hz and 10Hz. Current Noise 100 50nV/div Voltage Noise (nV/√Hz) Current Noise (fA/√Hz) 1000 Voltage Noise 10 1 1 10 100 1k 10k 1sec/div Frequency (Hz) TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY CHANNEL SEPARATION vs FREQUENCY 1 140 120 THD+Noise (%) Channel Separation (dB) VOUT = 3.5Vrms 100 Dual and quad devices. G = 1, all channels. Quad measured channel A to D or B to C—other combinations yield similar or improved rejection. 80 60 0.1 G = 10, RL = 2kΩ, 10kΩ 0.01 G = 1, RL = 2kΩ, 10kΩ 0.001 40 10 100 1k 10k 100k 10 1M Frequency (Hz) 1k Frequency (Hz) ® OPA277, 2277, 4277 100 4 10k 100k TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VS = ±15V, and RL = 2kΩ, unless otherwise noted. OFFSET VOLTAGE DRIFT PRODUCTION DISTRIBUTION OFFSET VOLTAGE PRODUCTION DISTRIBUTION 16 12 Typical distribution of packaged units. Single, dual, and quad included. 30 Percent of Amplifiers (%) 10 8 6 4 25 20 15 10 5 2 0 0 –50–45–40–35–30–25–20–15–10 –5 0 5 10 15 20 25 30 35 40 45 50 Offset Voltage (µV) 0 0.1 0.4 0.5 0.6 0.7 0.8 0.9 1.0 AOL, CMR, PSR vs TEMPERATURE 3 160 2 150 AOL, CMR, PSR (dB) Offset Voltage Change (µV) 0.3 Offset Voltage (µV/°C) WARM-UP OFFSET VOLTAGE DRIFT 1 0 –1 –2 CMR 140 AOL 130 PSR 120 110 –3 0 15 30 45 60 75 90 105 100 –75 120 –50 –25 0 25 50 75 100 Time from Power Supply Turn-On (s) Temperature (°C) INPUT BIAS CURRENT vs TEMPERATURE QUIESCENT CURRENT AND SHORT-CIRCUIT CURRENT vs TEMPERATURE 125 5 1000 100 4 950 90 3 900 80 Quiescent Current (µA) Input Bias Current (nA) 0.2 2 1 0 –1 –2 Curves represent typical production units. 70 850 ±IQ 800 60 50 750 –ISC 700 40 +ISC 650 30 600 20 –4 550 10 –5 500 –75 –3 –75 –50 –25 0 25 50 75 100 125 Temperature (°C) Short-Circuit Current (mA) Percent of Amplifiers (%) 35 Typical distribution of packaged units. Single, dual, and quad included. 14 0 –50 –25 0 25 50 75 100 125 Temperature (°C) ® 5 OPA277, 2277, 4277 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VS = ±15V, and RL = 2kΩ, unless otherwise noted. CHANGE IN INPUT BIAS CURRENT vs POWER SUPPLY VOLTAGE CHANGE IN INPUT BIAS CURRENT vs COMMON-MODE VOLTAGE 2.0 2.0 Curve shows normalized change in bias current with respect to VS = ±10V (+20V). Typical IB may range from –0.5nA to +0.5nA at VS = ±10V. 1.5 1.0 VS = ±5V 0.5 0.0 ∆IB (nA) ∆IB (nA) 1.0 Curve shows normalized change in bias current with respect to VCM = 0V. Typical IB may range from –05.nA to +0.5nA at VCM = 0V. 1.5 VCM = 0V 0.5 0.0 –0.5 –0.5 –1.0 –1.0 –1.5 –1.5 VS = ±15V –2.0 –2.0 0 5 10 15 20 25 30 35 40 –15 –10 Supply Voltage (V) QUIESCENT CURRENT vs SUPPLY VOLTAGE 5 10 15 100 10V step CL = 1500pF per amplifier Settling Time (µs) 900 800 700 50 0.01% 0.1% 20 600 10 500 0 ±5 ±10 ±15 ±20 ±1 ±10 Supply Voltage (V) ±100 Gain (V/V) MAXIMUM OUTPUT VOLTAGE vs FREQUENCY OUTPUT VOLTAGE SWING vs OUTPUT CURRENT (V+) 30 (V+) – 1 Output Voltage Swing (V) VS = ±15V 25 Output Voltage (Vp-p) 0 SETTLING TIME vs CLOSED-LOOP GAIN 1000 Quiescent Current (µA) –5 Common-Mode Voltage (V) 20 15 10 VS = ±5V 5 –55°C (V+) – 2 (V+) – 3 125°C (V+) – 4 25°C (V+) – 5 (V–) + 5 25°C 125°C (V–) + 4 (V–) + 3 (V–) + 2 –55°C (V–) + 1 (V–) 0 10k 1k 100k 1M 0 ® OPA277, 2277, 4277 ±5 ±10 ±15 ±20 Output Current (mA) Frequency (Hz) 6 ±25 ±30 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VS = ±15V, and RL = 2kΩ, unless otherwise noted. LARGE-SIGNAL STEP RESPONSE G = +1, CL = 1500pF, VS = ±15V SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE 60 Gain = –1 40 2V/div Gain = +1 30 20 Gain = ±10 10 0 10 100 1k 10k 100k 10µs/div Load Capacitance (pF) SMALL-SIGNAL STEP RESPONSE G = +1, CL = 1500pF, VS = ±15V SMALL-SIGNAL STEP RESPONSE G = +1, CL = 0, VS = ±15V 20mV/div 20mV/div Overshoot (%) 50 1µs/div 1µs/div ® 7 OPA277, 2277, 4277 APPLICATIONS INFORMATION connecting a potentiometer as shown in Figure 1. This adjustment should be used only to null the offset of the op amp. This adjustment should not be used to compensate for offsets created elsewhere in a system since this can introduce additional temperature drift. The OPA277 series is unity-gain stable and free from unexpected output phase reversal, making it easy to use in a wide range of applications. Applications with noisy or high impedance power supplies may require decoupling capacitors close to the device pins. In most cases 0.1µF capacitors are adequate. V+ Trim Range: Exceeds Offset Voltage Specification The OPA277 series has very low offset voltage and drift. To achieve highest performance, circuit layout and mechanical conditions should be optimized. Offset voltage and drift can be degraded by small thermoelectric potentials at the op amp inputs. Connections of dissimilar metals will generate thermal potential which can degrade the ultimate performance of the OPA277 series. These thermal potentials can be made to cancel by assuring that they are equal in both input terminals. 0.1µF 20kΩ 7 1 2 8 OPA277 3 0.1µF 4 6 OPA277 single op amp only. Use offset adjust pins only to null offset voltage of op amp—see text. V– • Keep thermal mass of the connections made to the two input terminals similar. • Locate heat sources as far as possible from the critical input circuitry. • Shield op amp and input circuitry from air currents such as cooling fans. FIGURE 1. OPA277 Offset Voltage Trim Circuit. INPUT PROTECTION The inputs of the OPA277 series are protected with 1kΩ series input resistors and diode clamps. The inputs can withstand ±30V differential inputs without damage. The protection diodes will, of course, conduct current when the inputs are over-driven. This may disturb the slewing behavior of unity-gain follower applications, but will not damage the op amp. OPERATING VOLTAGE OPA277 series op amp operate from ±2V to ±18V supplies with excellent performance. Unlike most op amps which are specified at only one supply voltage, the OPA277 series is specified for real-world applications; a single limit applies over the ±5V to ±15V supply range. This allows a customer operating at VS = ±10V to have the same assured performance as a customer using ±15V supplies. In addition, key parameters are guaranteed over the specified temperature range, –40°C to +85°C. Most behavior remains unchanged through the full operating voltage range (±2V to ±18V). Parameters which vary significantly with operating voltage or temperature are shown in typical performance curves. INPUT BIAS CURRENT CANCELLATION The input stage base current of the OPA277 series is internally compensated with an equal and opposite cancellation circuit. The resulting input bias current is the difference between the input stage base current and the cancellation current. This residual input bias current can be positive or negative. When the bias current is canceled in this manner, the input bias current and input offset current are approximately the same magnitude. As a result, it is not necessary to use a bias current cancellation resistor as is often done with other op amps (Figure 2). A resistor added to cancel input bias current errors may actually increase offset voltage and noise. OFFSET VOLTAGE ADJUSTMENT The OPA277 series is laser-trimmed for very low offset voltage and drift so most circuits will not require external adjustment. However, offset voltage trim connections are provided on pins 1 and 8. Offset voltage can be adjusted by R2 R2 R1 R1 Op Amp OPA277 RB = R2 || R1 No bias current cancellation resistor (see text) (a) (b) Conventional op amp with external bias current cancellation resistor. OPA277 with no external bias current cancellation resistor. FIGURE 2. Input Bias Current Cancellation. ® OPA277, 2277, 4277 8 V+ 1/2 OPA2277 VOUT = (V1 – V2)(1 + R2 R1 ) R2 V– R–∆R Load Cell V1 R+∆R V+ R+∆R V2 R1 1/2 OPA2277 R–∆R V– R2 R1 For integrated solution see: INA126, INA2126 (dual) INA125 (on-board reference) INA122 (single-supply) FIGURE 3. Load Cell Amplifier. IREG ∼ 1mA 5V 12 V+ Type J VLIN 1/2 OPA2277 13 RF 10kΩ 4 R 412Ω + VIN 1 IR1 3 11 VREG 10 V+ RG RG 1250Ω RF 10kΩ 14 IR2 XTR105 B E RG 9 8 IO 1/2 OPA2277 1kΩ 2 25Ω 7 IRET V– 50Ω – VIN 6 + – IO = 4mA + (VIN – VIN) 40 RG RCM = 1250Ω (G = 1 + 2RF = 50) R 0.01µF FIGURE 4. Thermocouple Low Offset, Low Drift Loop Measurement with Diode Cold Junction Compensation. ® 9 OPA277, 2277, 4277 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. Customers are responsible for their applications using TI components. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI’s publication of information regarding any third party’s products or services does not constitute TI’s approval, warranty or endorsement thereof. Copyright 2000, Texas Instruments Incorporated