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| (R) INA1 11 INA111 INA1 11 High Speed FET-Input INSTRUMENTATION AMPLIFIER FEATURES q FET INPUT: IB = 20pA max q HIGH SPEED: TS = 4s (G = 100, 0.01%) q LOW OFFSET VOLTAGE: 500V max q LOW OFFSET VOLTAGE DRIFT: 5V/C max q HIGH COMMON-MODE REJECTION: 106dB min q 8-PIN PLASTIC DIP, SOL-16 SOIC DESCRIPTION The INA111 is a high speed, FET-input instrumentation amplifier offering excellent performance. The INA111 uses a current-feedback topology providing extended bandwidth (2MHz at G = 10) and fast settling time (4s to 0.01% at G = 100). A single external resistor sets any gain from 1 to over 1000. Offset voltage and drift are laser trimmed for excellent DC accuracy. The INA111's FET inputs reduce input bias current to under 20pA, simplifying input filtering and limiting circuitry. The INA111 is available in 8-pin plastic DIP, and SOL-16 surface-mount packages, specified for the -40C to +85C temperature range. APPLICATIONS q MEDICAL INSTRUMENTATION q DATA ACQUISITION V+ 7 (13) - VIN INA111 2 (4) 1 (2) RG 8 (15) + VIN 3 (5) A2 10k 10k 25k 5 (10) Ref 25k A3 6 (11) Feedback A1 10k 10k (12) DIP Connected Internally VO G=1+ 50k RG 4 (7) DIP V- (SOIC) International 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/ * FAXLine: (800) 548-6133 (US/Canada Only) * Cable: BBRCORP * Telex: 066-6491 * FAX: (520) 889-1510 * Immediate Product Info: (800) 548-6132 (R) (c) 1992 Burr-Brown Corporation PDS-1143E 1 Printed in U.S.A. March, 1998 INA111 SBOS015 SPECIFICATIONS ELECTRICAL At TA = +25C, VS = 15V, RL = 2k, unless otherwise noted. INA111BP, BU PARAMETER CONDITIONS MIN TYP MAX MIN INA111AP, AU TYP MAX UNITS INPUT Offset Voltage, RTI Initial TA = +25C vs Temperature TA = TMIN to TMAX vs Power Supply VS = 6V to 18V Impedance, Differential Common-Mode Input Common-Mode Range VDIFF = 0V Common-Mode Rejection VCM = 10V, RS = 1k G=1 G = 10 G = 100 G = 1000 BIAS CURRENT OFFSET CURRENT NOISE VOLTAGE, RTI f = 100Hz f = 1kHz f = 10kHz fB = 0.1Hz to 10Hz Noise Current f = 10kHz GAIN Gain Equation Range of Gain Gain Error G = 1000, RS = 0 10 80 96 106 106 100 500/G 2 10/G 2 +10/G 1012 || 6 1012 || 3 12 90 110 115 115 2 0.1 13 10 10 1 0.8 1 + (50k/RG) 500 2000/G 5 100/G 30 + 100/G T 75 90 100 100 20 10 200 500/G 2 20/G T T T T T T T T T T T T T T T T 1000 5000/G 10 100/G T V V/C V/V || pF || pF V dB dB dB dB T T pA pA nV/Hz nV/Hz nV/Hz Vp-p fA/Hz V/V V/V % % % % ppm/C ppm/C % % % % of of of of FSR FSR FSR FSR 1 G = 1, RL = 10k G = 10, RL = 10k G = 100, RL = 10k G = 1000, RL = 10k G=1 G=1 G = 10 G = 100 G = 1000 IO = 5mA, TMIN to TMAX 11 0.01 0.1 0.15 0.25 1 25 0.0005 0.001 0.001 0.005 12.7 1000 +30/-25 2 2 450 50 17 2 2 4 30 1 6 VIN = 0V -40 -40 100 15 3.3 Gain vs Temperature 50k Resistance(1) Nonlinearity 10000 0.02 0.5 0.5 1 10 100 0.005 0.005 0.005 0.02 T T T T T T T T T T T T T T T T T T T T T T T T T T 0.05 T 0.7 2 T T T 0.01 0.01 0.04 OUTPUT Voltage Load Capacitance Stability Short Circuit Current FREQUENCY RESPONSE Bandwidth, -3dB V pF mA MHz MHz kHz kHz V/s s s s s s T T T T V mA C C C/W Slew Rate Settling Time, 0.01% Overload Recovery POWER SUPPLY Voltage Range Current TEMPERATURE RANGE Specification Operating JA G=1 G = 10 G = 100 G = 1000 VO = 10V, G = 2 to 100 G=1 G = 10 G = 100 G = 1000 50% Overdrive 18 4.5 85 125 T T T T T T T Specification same as INA111BP. NOTE: (1) Temperature coefficient of the "50k" term in the gain equation. 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. (R) INA111 2 PIN CONFIGURATIONS Top View DIP ELECTROSTATIC DISCHARGE SENSITIVITY 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. 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. ORDERING INFORMATION PRODUCT PACKAGE 8-Pin Plastic DIP 8-Pin Plastic DIP SOL-16 Surface-Mount SOL-16 Surface-Mount TEMPERATURE RANGE -40C -40C -40C -40C to to to to +85C +85C +85C +85C INA111AP INA111BP INA111AU INA111BU RG V-IN V + IN 1 2 3 4 8 7 6 5 RG V+ VO Ref V- Top View NC RG NC V-IN V+IN NC V- NC 1 2 3 4 5 6 7 8 SOL-16 Surface Mount 16 NC 15 RG 14 NC 13 V+ 12 Feedback 11 VO 10 Ref 9 NC PACKAGE INFORMATION PRODUCT INA111AP INA111BP INA111AU INA111BU PACKAGE 8-Pin Plastic 8-Pin Plastic 16-Pin Surface 16-Pin Surface DIP DIP Mount Mount PACKAGE DRAWING NUMBER(1) 006 006 211 211 ABSOLUTE MAXIMUM RATINGS(1) Supply Voltage .................................................................................. 18V Input Voltage Range .......................................... (V-) -0.7V to (V+) +15V Output Short-Circuit (to ground) .............................................. Continuous Operating Temperature ................................................. -40C to +125C Storage Temperature ..................................................... -40C to +125C Junction Temperature .................................................................... +150C Lead Temperature (soldering, 10s) ............................................... +300C NOTE: Stresses above these ratings may cause permanent damage. NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (R) 3 INA111 TYPICAL PERFORMANCE CURVES At TA = +25C, VS = 15V, unless otherwise noted. GAIN vs FREQUENCY 10k COMMON-MODE REJECTION vs FREQUENCY 120 Common-Mode Rejection (dB) G = 1k 1k G = 100 100 G = 10 100 80 60 G = 100 40 G = 10 20 G=1 0 Gain (V/V) G = 1k 10 G=1 1 0.1 1k 10k 100k Frequency (Hz) 1M 10M 10 100 1k 10k 100k 1M Frequency (Hz) INPUT COMMON-MODE VOLTAGE RANGE vs OUTPUT VOLTAGE 15 Common-Mode Voltage (V) 10 5 0 -5 -10 -15 -15 y A1 ed b Limit ut Swing tp + Ou VD/2 POWER SUPPLY REJECTION vs FREQUENCY 120 - + - + (Any Gain) VO Power Supply Rejection (dB) Limit + Ou ed by A tput Swin2 g 100 80 60 40 20 0 G = 1k G = 100 G = 10 G=1 VD/2 VCM Lim it - O ed by utpu A t Sw 2 ing -10 A3 - Output Swing Limit A3 + Output Swing Limit by A 1 g in ited Lim put Sw t Ou - -5 0 5 10 15 10 100 1k 10k 100k 1M Output Voltage (V) Frequency (Hz) INPUT-REFERRED NOISE VOLTAGE vs FREQUENCY 1k 100 SETTLING TIME vs GAIN Input-Referred Noise Voltage (nV/Hz) 100 G=1 Settling Time (s) 10 0.01% G = 10 10 G = 100, 1k 0.1% 1 1 10 100 Frequency (Hz) 1k 10k 1 1 10 Gain (V/V) 100 1000 (R) INA111 4 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25C, VS = 15V, unless otherwise noted. OFFSET VOLTAGE WARM-UP vs TIME 75 Referred-to-Input VOS Change (V) INPUT BIAS CURRENT vs TEMPERATURE 300 200 100 0 -100 Referred-to-Input VOS Change (V) 10n 1n Input Bias Current (A) Ib IOS 50 25 0 -25 G=1 -50 -75 0 1 2 3 4 5 Time From Power Supply Turn-On (Minutes) 100p 10p 1p 0.1p 0.01p -75 -50 -25 0 25 50 75 100 125 Temperature (C) G 10 -200 -300 INPUT BIAS CURRENT vs DIFFERENTIAL INPUT VOLTAGE -10m -1m -15.7V -10m INPUT BIAS CURRENT vs COMMON-MODE INPUT VOLTAGE -15.7V Input Bias Current (A) -100 -10 G=1 +1p G = 10 +10p +100p -20 -15 -10 -5 0 5 10 Differential Overload Voltage (V) NOTE: One input grounded. G = 1k G = 100 +15.7V 15 20 G=1 G = 10 G = 100 G = 1k Input Bias Current (A) -1m -100 -10 +1p +15.7V +10p -20 -15 -10 -5 0 5 10 15 20 Common-Mode Voltage (V) MAXIMUM OUTPUT VOLTAGE SWING vs FREQUENCY 30 Peak-to-Peak Amplitude (V) 25 20 15 10 5 0 1k 10k 100k Frequency (Hz) 1M 10M 50 OUTPUT CURRENT LIMIT vs TEMPERATURE Short-Circuit Current (mA) 40 30 -ICL 20 +ICL 10 0 -75 -50 -25 0 25 50 75 100 125 Temperature (C) (R) 5 INA111 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25C, VS = 15V, unless otherwise noted. QUIESCENT CURRENT vs TEMPERATURE 3.5 1 TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY VO = 3Vrms, RL = 2k Measurement BW = 80kHz Quiescent Current (mA) 3.4 THD + N (%) 0.1 G = 1k Single-Ended Drive G = 1 3.3 0.01 G = 100 G = 10 3.2 0.001 3.1 0.0001 Differential Drive G = 1 3.0 -75 -50 -25 0 25 50 75 100 125 Temperature (C) 20 100 1k Frequency (Hz) 10k 20k LARGE SIGNAL RESPONSE, G = 100 SMALL SIGNAL RESPONSE, G = 1 +10 +0.1 0 0 -0.1 -10 0 10 Time (s) 20 0 10 Time (s) 20 LARGE SIGNAL RESPONSE, G = 100 SMALL SIGNAL RESPONSE, G = 1 +10 +0.1 0 0 -10 -0.1 0 10 Time (s) 20 0 10 Time (s) 20 (R) INA111 6 APPLICATION INFORMATION Figure 1 shows the basic connections required for operation of the INA111. Applications with noisy or high impedance power supplies may require decoupling capacitors close to the device pins as shown. The output is referred to the output reference (Ref) terminal which is normally grounded. This must be a low-impedance connection to assure good common-mode rejection. A resistance of 2 in series with the Ref pin will cause a typical device with 90dB CMR to degrade to approximately 80dB CMR (G = 1). SETTING THE GAIN Gain of the INA111 is set by connecting a single external resistor, RG: G = 1 + 5 0k RG The 50k term in equation 1 comes from the sum of the two internal feedback resistors. These are on-chip metal film resistors which are laser trimmed to accurate absolute values. The accuracy and temperature coefficient of these resistors are included in the gain accuracy and drift specifications of the INA111. The stability and temperature drift of the external gain setting resistor, RG, also affects gain. RG's contribution to gain accuracy and drift can be directly inferred from the gain equation (1). Low resistor values required for high gain can make wiring resistance important. Sockets add to the wiring resistance, which will contribute additional gain error (possibly an unstable gain error) in gains of approximately 100 or greater. DYNAMIC PERFORMANCE The typical performance curve "Gain vs Frequency" shows that the INA111 achieves wide bandwidth over a wide range of gain. This is due to the current-feedback topology of the INA111. Settling time also remains excellent over wide gains. (1) Commonly used gains and resistor values are shown in Figure 1. V+ 0.1F Pin numbers are for DIP package. - VIN 2 A1 1 25k RG 8 25k A2 10k 10k 5 Ref A3 6 + 7 INA111 - VO = G * (VIN - VIN) + 10k 10k 50k G=1+ RG Load VO - + VIN 3 4 0.1F DESIRED GAIN 1 2 5 10 20 50 100 200 500 1000 2000 5000 10000 RG () No Connection 50.00k 12.50k 5.556k 2.632k 1.02k 505.1 251.3 100.2 50.05 25.01 10.00 5.001 NEAREST 1% RG () No Connection 49.9k 12.4k 5.62k 2.61k 1.02k 511 249 100 49.9 24.9 10 4.99 Also drawn in simplified form: V- - VIN RG + VIN INA111 Ref VO FIGURE 1. Basic Connections (R) 7 INA111 The INA111 exhibits approximately 6dB rise in gain at 2MHz in unity gain. This is a result of its current-feedback topology and is not an indication of instability. Unlike an op amp with poor phase margin, the rise in response is a predictable +6dB/octave due to a response zero. A simple pole at 700kHz or lower will produce a flat passband response (see Input Filtering). The INA111 provides excellent rejection of high frequency common-mode signals. The typical performance curve, "Common-Mode Rejection vs Frequency" shows this behavior. If the inputs are not properly balanced, however, common-mode signals can be converted to differential sig- + nals. Run the VIN and VIN connections directly adjacent each other, from the source signal all the way to the input pins. If possible use a ground plane under both input traces. Avoid running other potentially noisy lines near the inputs. NOISE AND ACCURACY PERFORMANCE The INA111's FET input circuitry provides low input bias current and high speed. It achieves lower noise and higher accuracy with high impedance sources. With source impedances of 2k to 50k the INA114 may provide lower offset voltage and drift. For very low source impedance (1k), the INA103 may provide improved accuracy and lower noise. OFFSET TRIMMING The INA111 is laser trimmed for low offset voltage and drift. Most applications require no external offset adjustment. Figure 2 shows an optional circuit for trimming the output offset voltage. The voltage applied to Ref terminal is summed at the output. Low impedance must be maintained at this node to assure good common-mode rejection. The op amp shown maintains low output impedance at high frequency. Trim circuits with higher source impedance should be buffered with an op amp follower circuit to assure low impedance on the Ref pin. INPUT BIAS CURRENT RETURN PATH The input impedance of the INA111 is extremely high-- approximately 1012. However, a path must be provided for the input bias current of both inputs. This input bias current is typically less than 10pA. High input impedance means that this input bias current changes very little with varying input voltage. Input circuitry must provide a path for this input bias current if the INA111 is to operate properly. Figure 3 shows various provisions for an input bias current path. Without a bias current return path, the inputs will float to a potential which exceeds the common-mode range of the INA111 and the input amplifiers will saturate. If the differential source resistance is low, the bias current return path can be connected to one input (see the thermocouple example in Figure 3). With higher source impedance, using two resistors provides a balanced input with possible advantages of lower input offset voltage due to bias current and better high-frequency common-mode rejection. Crystal or Ceramic Transducer INA111 1M 1M Thermocouple INA111 10k INA111 VIN RG + VIN INA111 Ref - VO V+ 100A 1/2 REF200 Center-tap provides bias current return. OPA177 10mV Adjustment Range 100(1) 10k (1) FIGURE 3. Providing an Input Common-Mode Current Path. INPUT COMMON-MODE RANGE The linear common-mode range of the input op amps of the INA111 is approximately 12V (or 3V from the power supplies). As the output voltage increases, however, the linear input range will be limited by the output voltage swing of the input amplifiers, A1 and A2. The common-mode range is related to the output voltage of the complete amplifier-- see performance curve "Input Common-Mode Range vs Output Voltage". 100(1) NOTE: (1) For wider trim range required in high gains, scale resistor values larger V- 100A 1/2 REF200 FIGURE 2. Optional Trimming of Output Offset Voltage. (R) INA111 8 A combination of common-mode and differential input voltage can cause the output of A1 or A2 to saturate. Figure 4 shows the output voltage swing of A1 and A2 expressed in terms of a common-mode and differential input voltages. For applications where input common-mode range must be maximized, limit the output voltage swing by connecting the INA111 in a lower gain (see performance curve "Input Common-Mode Voltage Range vs Output Voltage"). If necessary, add gain after the INA111 to increase the voltage swing. Input-overload often produces an output voltage that appears normal. For example, consider an input voltage of +14V on one input and +15V on the other input will obviously exceed the linear common-mode range of both input amplifiers. Since both input amplifiers are saturated to the nearly the same output voltage limit, the difference voltage measured by the output amplifier will be near zero. The output of the INA111 will be near 0V even though both inputs are overloaded. INPUT PROTECTION Inputs of the INA111 are protected for input voltages from 0.7V below the negative supply to 15V above the positive power supply voltages. If the input current is limited to less than 1mA, clamp diodes are not required; internal junctions will clamp the input voltage to safe levels. If the input source can supply more than 1mA, use external clamp diodes as shown in Figure 5. The source current can be limited with series resistors R1 and R2 as shown. Resistor values greater than 10k will contribute noise to the circuit. A diode formed with a 2N4117A transistor as shown in Figure 5 assures low leakage. Common signal diodes such as the 1N4148 may have leakage currents far greater than the input bias current of the INA111 and are usually sensitive to light. INPUT FILTERING The INA111's FET input allows use of an R/C input filter without creating large offsets due to input bias current. Figure 6 shows proper implementation of this input filter to preserve the INA111's excellent high frequency commonmode rejection. Mismatch of the common-mode input capacitance (C1 and C2), either from stray capacitance or V+ D1 VIN R1 + VIN - D2 R2 RG INA111 VO D3 D4 V+ 2N4117A 1pA Leakage Diodes: = FIGURE 5. Input Protection Voltage Clamp. VCM - G * VD 2 V+ INA111 A1 VD 2 10k 25k RG 25k A2 VCM G * VD 2 10k 10k A3 10k G=1+ 50k RG VO = G * VD VD 2 VCM + V- FIGURE 4. Voltage Swing of A1 and A2. (R) 9 INA111 mismatched values, causes a high frequency common-mode signal to be converted to a differential signal. This degrades common-mode rejection. The differential input capacitor, C3, reduces the bandwidth and mitigates the effects of mismatch in C1 and C2. Make C3 much larger than C1 and C2. If properly matched, C1 and C2 also improve CMR. OUTPUT VOLTAGE SENSE (SOL-16 Package Only) The surface-mount version of the INA111 has a separate output sense feedback connection (pin 12). Pin 12 must be connected, usually to the output terminal, pin 11, for proper operation. (This connection is made internally on the DIP version of the INA111.) The output feedback connection can be used to sense the output voltage directly at the load for best accuracy. Figure 8 shows how to drive a load through series interconnection resistance. Remotely located feedback paths may cause instability. This can be generally be eliminated with a high frequency feedback path through C1. Surface-mount package version only. - VIN RG + VIN Feedback INA111 Ref C1 1000pF Load Equal resistance here preserves good common-mode rejection. FIGURE 8. Remote Load and Ground Sensing. C1 C2 RG INA111 Ref VO R1 R2 fc = f-3 d B = C1 VIN C3 - R1 1 C 4 R1 C 3 + 1 2 VO 1 2R1C1 NOTE: To preserve good low frequency CMR, make R1 = R2 and C1 = C2. R2 + VIN INA111 Ref FIGURE 9. High-Pass Input Filter. C2 R1 = R2 C1 = C2 C3 10C1 6V to 18V Isolated Power V+ V- 15V FIGURE 6. Input Low-Pass Filter. - VIN INA111 +10V + VIN ISO122 VO Ref G = 500 Bridge RG 100 INA111 Ref VO Isolated Common FIGURE 10. Galvanically Isolated Instrumentation Amplifier. FIGURE 7. Bridge Transducer Amplifier. (R) INA111 10 VIN OPA177 - VIN + RG INA111 Ref C1 0.1F VO C1 50nF R1 1M R1 10k INA111 RG R2 VIN G * R2 OPA602 1 f-3dB = 2R1C1 = 1.59Hz Ref IL = Make G 10 where G = 1 + 50k RG Load FIGURE 11. AC-Coupled Instrumentation Amplifier. FIGURE 12. Voltage Controlled Current Source. VIN + VIN - 22.1k 22.1k 511 INA111 Ref VO 100 NOTE: Driving the shield minimizes CMR degradation due to unequally distributed capacitance on the input line. The shield is driven at approximately 1V below the common-mode input voltage. OPA602 For G = 100 RG = 511 // 2(22.1k) effective RG = 505 FIGURE 13. Shield Driver Circuit. +5V + - MPC800 MUX Channel 8 VIN + - RG INA111 Ref ADS574 12 Bits Out Channel 1 VIN FIGURE 14. Multiplexed-Input Data Acquisition System. (R) 11 INA111 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 (c) 2000, Texas Instruments Incorporated |
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