® INA104 Very-High Accuracy INSTRUMENTATION AMPLIFIER FEATURES DESCRIPTION ● VERSATILE FOUR OP AMP DESIGN The INA104 is a high accuracy, multistage, integrated-circuit instrumentation amplifier designed for signal conditioning requirements where very high performance is desired. A multiamplifier, monolithic design, which uses BurrBrown’s ultra-low drift, low-noise technology, provides the highest performance with maximum versatility at the lowest cost and makes the INA104 ideal for even high volume applications. Burr-Brown’s compatible thin-film resistors and lasertrimming techniques are used for minimizing offset voltage and temperature drift. This advanced technique also maximizes common-mode rejection and gain accuracy. The INA104 also contains a fourth operational amplifier, specified separately, which can conveniently be used for some important applications such as single capacitor active low-pass filtering, easy output level shifting, common-mode voltage active guard drive, and increased gain (x 10,000 and greater). ● ULTRA-LOW VOLTAGE DRIFT: 0.25µV/°C, max ● LOW OFFSET VOLTAGE: 25µV, max ● LOW NONLINEARITY: 0.002%, max ● LOW NOISE: 13nV/√ Hz at f0 = 1kHz ● HIGH CMR: 106dB at 60Hz, min ● HIGH INPUT IMPEDANCE: 1010Ω ● LOW COST APPLICATIONS ● AMPLIFICATION OF SIGNALS FROM SOURCES SUCH AS: Strain Gages Thermocouples RTDs ● REMOTE TRANSDUCER AMPLIFIER ● LOW LEVEL SIGNAL CONDITIONER ● MEDICAL INSTRUMENTATION A3 A4 Output Inverting Input 8 Gain Gain Sense –In 14 9 20kΩ 18 10kΩ 10kΩ 10kΩ 10kΩ A1 17 12 A4 Summing Junction 11 Feedback Resistor 26kΩ CMV Sense Gain Gain Sense +In 4 5 26kΩ 20kΩ 1 10kΩ A3 A4 A4 Output 10kΩ 5kΩ A2 2 10 16 15 Offset Adjust Offset Adjust 13 +VCC 3 –VCC 6 Common 7 A4 Non-Inverting Input International Airport Industrial Park • Mailing Address: PO Box 11400 Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP • • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706 Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 ©1983 Burr-Brown Corporation PDS-488D Printed in U.S.A. May, 1995 SPECIFICATIONS—INSTRUMENTATION AMPLIFIER At TA = +25°C, VS = ±15V power supply and in circuit of Figure 1 unless otherwise noted. INA104AM PARAMETER MIN GAIN Range of Gain Gain Equation Error From Equation, DC(1) Gain Temp. Coefficient(2) G=1 G = 10 G = 100 G = 1000 Nonlinearity, DC RATED OUTPUT Voltage Current Output Impedance 1 ±10 ±5 INPUT OFFSET VOLTAGE Initial Offset at +25°C(3) vs Temperature vs Supply vs Time MIN 1000 * ±(0.15 –0.1/G) 2 20 22 22 ±(0.002 + 10–5G) 5 100 110 110 ±(0.005 + 2 x 10–5G) +11.5, –12.5 +11.5, –12.5 0.2 ±(1 + 50/G) ±(1 + 20/G) ±15 ±0.2 ±0.1 ±5 ±0.5 INPUT IMPEDANCE Differential Common-Mode MAX G = 1 + (40k/RG) ±(0.08 –0.05/G) ±25 ±200/G INPUT BIAS CURRENT Initial Bias Current (each input) vs Temperature vs Supply Initial Offset Current vs Temperature * * ±50 ±400/G ±2 ±20/G INPUT NOISE Input Voltage Noise fB = 0.1Hz to 10Hz Density, G = 1000 fO = 10Hz fO = 100Hz fO = 1kHz Input Current Noise fB = 0.01Hz to 10Hz Density fO = 10Hz fO = 100Hz fO = 1kHz 0.2 ±30 * * * * * * ±(0.001 + 10–5G) MAX MIN * * * * ±2 * ±30 UNITS * V/V V/V %of FS * * * * * ±(0.002 + 10–5G) * –10 –11 –11 ±(0.001 + 10–5G) * –50 –55 –55 ±(0.002 + 10–5G) * * * * * ±5 * * ±2 * * ±20 ±20 * * * * µV µV/°C µV/V µV/mo nA nA/°C nA/V nA nA/°C Ω || pF Ω || pF * * * * * ppm/°C ppm/°C ppm/°C ppm/°C % of FS, p-p V mA Ω ±10 ±100/G ±25 ±200/G ±0.25 ±10/G * * * * * * * MAX * * * 90 106 110 TYP * * * * * ±10 V * * * dB dB dB 0.8 * * µV, p-p 18 15 13 * * * * * * nV/√Hz nV/√Hz nV/√Hz 50 * * pA, p-p 0.8 0.46 0.35 * * * * * * pA/√Hz pA/√Hz pA/√Hz 300 140 25 2.5 * * * * * * * * kHz kHz kHz kHz 20 10 1 200 6.4 0.4 * * * * * * * * * * * * kHz kHz kHz Hz kHz V/µs * * 30 40 350 40 55 470 * * * * * * * * * * * * µs µs µs 30 50 500 45 70 650 * * * * * * * * * * * * µs µs µs ® INA104 TYP INA104CM ±10 ±100/G ±25 ±200/G ±0.75 ±10/G * * 1010 || 3 1010 || 3 INPUT VOLTAGE RANGE Range, Linear Response ±10 CMR with 1kΩ Source Imbalance DC to 60Hz, G = 1 80 DC to 60Hz, G = 10 96 DC to 60Hz, G = 100 to 1000 106 DYNAMIC RESPONSE Small Signal, ±3dB Flatness G=1 G = 10 G = 100 G = 1000 Small Signal, ±1% Flatness G=1 G = 10 G = 100 G = 1000 Full Power, G = 1 - 100 Slew Rate, G = 1 - 100 Settling Time (0.1%) G=1 G = 100 G = 1000 Settling Time (0.01%) G=1 G = 100 G = 1000 TYP INA104BM, SM 2 SPECIFICATIONS—OUTPUT AMPLIFIER, A4 At TA = +25°C, VS = ±15V power supply and in circuit of Figure 1 unless otherwise noted. INA104AM PARAMETER MIN TYP OPEN-LOOP GAIN, VO = ±100 Rated Load RL ≥ 2kΩ 100 RL ≥ 10kΩ 110 RATED OUTPUT Voltage at RL = 2kΩ RL = 10kΩ Current Output Impedance Load Capacitance (Unity-Gain Inverting) Short Circuit Current FREQUENCY RESPONSE Unity Gain, Small Signal Full Power Slew Rate Settling Time (Unity-Gain) 0.1% 0.01% 10 5 0.35 INA104BM, SM MAX MIN TYP 115 125 * * +13, –14.5 +13, –14.5 7.5 2 * * INA104CM MAX MIN TYP * * * * * * dB dB * * * * * * * * * V V mA kΩ * MAX UNITS 2000 10 * * * * pF mA 1 9 0.55 * * * * * * MHz kHz V/µs * * µs µs * 37 40 * * * INPUT OFFSET VOLTAGE Initial, TA = +25°C vs Temperature ±1 ±5 ±2 * * * * * * mV µV/°C INPUT BIAS CURRENT +55 +150 * * * * nA INPUT IMPEDANCE Differential Common-Mode 500 100 RESISTORS, 10kΩ Accuracy Drift Ratio Match Drift 0.5 30 0.06 5 INPUT VOLTAGE NOISE fB = 0.1Hz to 10Hz Density fO = 10Hz fO = 100Hz fO = 1kHz POWER SUPPLY Rated Voltage Voltage Range Quiescent Current TEMPERATURE RANGE Specification: AM, BM, CM SM Operation: AM, BM, CM, SM Storage: AM, BM, CM, SM θJC θJA ±5 * * 5 50 0.12 * * * * * * * * * * * * * kΩ MΩ * * * % ppm/°C % ppm/°C 1.5 * * µV, p-p 35 33 32 * * * * * * nV√ Hz nV√ Hz nV√ Hz ±15 * ±20 ±9.6 * –25 –55 +85 +125 –55 ±8.1 –65 * * * V V mA * * * * °C °C * * * °C * * * °C °C/W °C/W * * * * * * * +125 * +150 * * 115 130 * * * * * * Specifications same as for INA104AM. NOTES: (1) Typically the tolerance of RG will be the major source of gain error. (2) Not including the TCR of RG. (3) Adjustable to zero at any one gain. 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. ® 3 INA104 PIN CONFIGURATION ORDERING INFORMATION Top View PACKAGE TEMPERATURE RANGE 18-Pin Hermetic DIP 18-Pin Hermetic DIP 18-Pin Hermetic DIP 18-Pin Hermetic DIP –25°C to +85°C –25°C to +85°C –25°C to +85°C –55°C to +125°C DIP MODEL Gain Sense 1 18 Gain Sense +In 2 17 –In INA104AM INA104BM INA104CM INA104SM – Supply 3 16 Offset Adjust Common-Mode Voltage Sense 4 15 Offset Adjust Gain 5 14 Gain Common 6 13 +Supply Non-Inverting Input to A4 7 12 Summing Junction of A4 Output 8 11 Feedback Resistor MODEL Inverting Input to A4 9 10 Output of A4 INA104AM INA104BM INA104CM INA104SM PACKAGE INFORMATION(1) PACKAGE PACKAGE DRAWING NUMBER 18-Pin Hermetic DIP 18-Pin Hermetic DIP 18-Pin Hermetic DIP 18-Pin Hermetic DIP 108 108 108 108 NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix D of Burr-Brown IC Data Book. ABSOLUTE MAXIMUM RATINGS Supply ................................................................................................ ±20V Internal Power Dissipation ............................................................. 980mW Input Voltage Range ........................................................................... ±VCC Output Short-Circuit (to ground) .............................................. Continuous Operating Temperature ................................................. –40°C to +125°C Storage Temperature ..................................................... –40°C to +125°C Lead Temperature (soldering, 10s) ............................................... +300°C 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. USA OEM PRICES ® INA104 4 MODEL 1-24 25-99 100+ INA118P INA118PB INA118U INA118UB $5.40 8.10 5.40 8.10 $4.65 7.00 4.65 7.00 $3.85 5.80 3.85 5.80 TYPICAL PERFORMANCE CURVES At TA = +25°C, VCC = 15V, and in circuit of Figure 1, unless otherwise specified. CMR vs SOURCE IMBALANCE GAIN NONLINEARITY vs GAIN 120 G = 100 - 1000 G = 100 - 1000 G = 10 100 G = 10 0.003 Max CMR (dB) Gain Nonlinearity (% FS, p-p) 0.01 Typ G=1 80 G=1 0.001 60Hz DC 60 0.0003 40 1 10 100 10 1 1k 100 Gain (V/V) Source Resistance Imbalance (kΩ) TOTAL OFFSET VOLTAGE DRIFTvs GAIN GAIN vs FREQUENCY 3200 Output Voltage Drift (µV/°C) G = 1000 60 Gain (dB) 320 AM M ,S BM 32 G = 100 40 G = 10 20 1% Error G=1 CM 0 3.2 1 10 100 10 1k 100 1k 10k 100k 1M Frequency (Hz) Gain (V/V) GAIN ERROR vs FREQUENCY CMR vs FREQUENCY 100% 120 G = 100, 1000 G = 10 10% Gain Error (dB) CMR (dB) 100 G=1 80 Balanced Source G = 1000 1% G = 100 0.1% 60 G=1 G = 10 0.01% 40 1 10 100 1k 10 10k 100 1k 10k 100k Frequency (Hz) Frequency (Hz) ® 5 INA104 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VCC = 15V, and in circuit of Figure 1, unless otherwise specified. WARM-UP DRIFT vs TIME QUIESCENT CURRENT vs SUPPLY ±10 8 Quiescent Current (mA) Change Input Offset Voltage (µV) 10 6 4 2 ±9 ±8 ±7 ±6 0 0 3 6 9 12 15 0 ±5 Time (Minutes) ±10 ±15 ±20 Supply Voltage (V) STEP RESPONSE SETTLING TIME vs GAIN 1000 G = 1000 +5 Settling Time (µs) Output (V) RL = 2kΩ CL = 1000pF G=1 +10 0 –5 320 0.01% 0.1% 100 –10 1% 32 0 100 200 300 400 500 600 1 100 Gain (V/V) OUTPUT NOISE vs GAIN INPUT NOISE VOLTAGE vs FREQUENCY (100 ≤ GAIN ≤ 1000) 1k 1000 Input Noise Voltage (nV/√ Hz) 30 Output Noise Voltage (mV, rms) 10 Time (µs) 20 RS = 1MΩ 10 RS = 1000kΩ RS = 10kΩ RS = 0 100 10 1 0 1 10 100 1 1k ® INA104 10 100 Frequency (Hz) Gain (V/V) 6 1k DISCUSSION OF PERFORMANCE USING THE INA104 Figure 1 shows the simplest configuration of the INA104. The gain is set by the external resistor, RG, with a gain equation of G = 1 + (40k/RG). The accuracy and TCR of RG contribute directly to the gain accuracy and drift. For gains greater than unity, resistor RG is connected between pins 5 and 14. At high gains, where the value of RG becomes small, additional resistance (i.e., relays, sockets) in series with RG will contribute to gain error. Care should be taken to minimize this effect. However, this error can be virtually eliminated with the INA104 by using the Gain Sense circuit connection. Pins 1, 5, 14, and 18 are accessible so that a fourterminal connection can be made to RG. (Pins 1 and 18 are the voltage sense terminals, since no signal current flows into the operational amplifiers’ inputs.) This is useful at high gains, where the value of RG is small. The optional offset adjust capability is shown in Figure 1. The adjustment affects only the input stage component of the offset voltage. Thus, the null condition will be disturbed (if input offset is not adjusted to zero) when the gain is changed. Also, the input drift will be affected by approximately 0.31µV/°C per 100µV of input offset voltage that is trimmed. Therefore, care should be taken when considering use of the control for removal of other sources of offset. INSTRUMENTATION AMPLIFIERS Instrumentation amplifiers are closed-loop gain blocks whose committed circuitry accurately amplifies the voltage applied to their inputs. They respond only to the difference between the two input signals and exhibit extremely high input impedance, both differentially and common-mode. Feedback networks are packaged within the amplifier module. Only one external gain setting resistor must be added. An operational amplifier, on the other hand, is an open-loop, uncommitted device that requires external networks to close the loop. While operational amplifiers can be used to achieve the same basic function as instrumentation amplifiers, it is difficult to reach the same level of performance. Using operational amplifiers often leads to design trade-offs when it is necessary to amplify low level signals in the presence of commonmode voltages while maintaining high input impedances. THE INA104 A simplified schematic of the INA104 is shown on the front pages of this data sheet. It is a three-amplifier device which provides all the desirable characteristics of a premium performance instrumentation amplifier. In addition, it has features not normally found on integrated circuit instrumentation amplifiers. The input section (A1 and A2) incorporates high performance, low drift amplifier circuitry. The amplifiers are connected in the non-inverting configuration to provide the high input impedance (1010Ω) desirable in the instrumentation amplifier function. The offset voltage and offset voltage versus temperature is low due to the monolithic design and improved even further by the state-of-the-art, laser-trimming techniques. The output section (A3) is connected in a unity-gain difference amplifier configuration. A critical part of this stage is the matching of the four 10kΩ resistors which provide the difference function. These resistors must be initially well matched and the matching must be maintained over temperature and time in order to retain excellent common-mode rejection. (The 106dB minimum at 60Hz for gains greater than 100V/V is a significant improvement compared to most other integrated circuit instrumentation amplifiers.) All of the internal resistors are compatible, thin-film nichrome formed with the integrated circuit. The critical resistors are laser-trimmed to provide the desired high gain accuracy and common-mode rejection. Nichrome ensures long-term stability of trimmed resistors and excellent TCR and TCR tracking. This provides gain accuracy and common-mode rejection when the INA104 is operated over wide temperature ranges. The fourth op amp (A4) of the INA104 adds a great deal of versatility and convenience to the amplifier. It allows easy implementation of active low-pass filtering, output offsetting, and additional gain generation. The pin connections make the use of this stage optional and the specifications appear separately in the table of Specifications. This circuit may be used as replacement for the single potentiometer. It will adjust offset +VCC and leave drift unchanged. 2N2222 2MΩ Optional Offset Adjust +VCC 10MΩ 1µF Tantalum 13 17 18 E1 –In 100kΩ 16 100kΩ 16 15 Gain Sense 14 15 8 INA104 RG 1 2 EOUT 11 5 10 Gain Sense 7 6 (1) +In 3 EOUT = [1 = (40k/RG)] (E2 – E1) E2 –VCC 1µF Tantalum NOTE: (1) Connect pin 7 to common and pin 10 to pin 11 when Internal Amp A4 is not used. FIGURE 1. Basic Connection for the INA104 Including Optional Input Offset Null Potentiometer. ® 7 INA104 +VCC +VCC E8 = E6 13 17 13 EOUT = (E2 – E1)(1+ 40k/RG) + VOFFSET –In 17 18 E1 E1 14 5kΩ INA104 (1) RG 5 8 7 6 10 EOUT E2 R2 1kΩ Reference 8 7 1 12 EOUT 9 5 (1) A3 Output 6 R3 100kΩ 3 INA104 RG R1 1MΩ 10 +In 12 14 +15V 1 2 RF 18 2 3 E2 –15V –VCC –VCC A4, NOTE: (1) internal to the INA104. External amp (OPA27 or equivalent) may also be used. EOUT = (E1 – E2)[(1 + (40k/RG)](RF /10k) NOTE: (1) A4 inverts the output of the Instrumentation Amplifier, pin 8 to pin 10. Therefore, the equation for EOUT shows E1 – E2 instead of E2 – E1. FIGURE 2. Optional Output Offset Nulling or Offsetting Using an Amplifier (Low Impedance to Pin 6). FIGURE 3. Additional Gain From Output Stage. OPTIONAL OFFSET ADJUSTMENT PROCEDURE TYPICAL APPLICATIONS It is frequently desirable to null the input component of offset (Figure 1) and occasionally that of the output (Figure 2). The quality of the potentiometer will affect the results, therefore, choose one with good temperature and mechanical-resistance stability. The procedure is as follows: 1. Set E1 = E2 = 0V (be sure a good ground return path exists to the input). 2. Set the gain to the desired value (greater than 1) by choosing RG. 3. Adjust the 100kΩ potentiometer in Figure 1 until the output reads 0V ±1mV or desired setting. Note that the offset will change when the gain is changed. 4. If the output component of offset is to be removed or if it is desired to establish an intentional offset, adjust the 100kΩ potentiometer in Figure 2 until the output reads 0V ±1mV or desired setting. Note that the offset will not change with gain, but be sure to use a stable amplifier with good DC characteristics. The range of adjustment is ±15mV as shown. For larger ranges, change the ratio of R1 to R2. The op amp is used to maintain a low resistance (<0.1Ω) from pin 6 to Common to avoid CMR degradation. Many applications of instrumentation amplifiers involve the amplification of low-level differential signals from bridges and transducers such as strain gages, thermocouples, and RTDs. Some of the important parameters include commonmode rejection (differential cancellation of common-mode offset and noise), input impedance, offset voltage and drift, gain accuracy, linearity, and noise. The INA104 accomplishes all of these with high precision. Figure 3 shows how the output stage may be used to provide additional gain. If gains greater than 1000V/V (10,000 up to 100,000 and greater) are desired, it is better to place some gain in the output amplifier rather than the input stage due +VCC 13 EOUT = (E1 – E2)[1 + (40k/RG)] + 2VREF 17 18 E1 11 14 10 BASIC CIRCUIT CONNECTION The basic circuit connection for the INA104 is shown in Figure 1. The output voltage is a function of the differential input voltage times the gain. Figure 1 does not include additional internal op amp A4. Power supply bypassing with a 1µF tantalum capacitor or equivalent is always recommended. EOUT 9 5 8 7 1 (1) 6 2 VREF 3 E2 In applications which do not use the fourth internal amplifier (A4—pins 7, 9, 10, 11, and 12), pin 7 should be connected to Common and pins 10 and 11 should be connected together. This will prevent the output of A4 from saturating (“locking-up”) and affecting the offset of the instrumentation amplifier, A1, A2, and A3. –VCC –VCC NOTE: (1) A4 inverts, see Figure 3. FIGURE 4. Output Offsetting. ® INA104 INA104 RG 8 +VCC R R = a convenient value (<100kΩ typically) +VCC 13 17 Shield –In 18 14 5 E1 4 7 1 2 E2 8 5kΩ INA104 (1) RG EOUT CMV Sense 6 10 +In 3 12 EOUT = [E2 – E1 + (ECM/CMRR)](1 + 40k/RG) ECM –VCC NOTE: Internal Op Amp, A4, or External Amp (OPA27 or equivalent). FIGURE 5. Use of Guard Drive. +VCC +VCC fP = (1/2πCF104)Hz CF in farads used with A4. 13 13 CF 17 17 18 18 12 E1(f) 14 E1 10 INA104 RG 5 10 EOUT (1) 8 7 1 (1) 6 6 2 2 EOUT 9 5 8 7 INA104 RG 9 1 11 14 11 Current Booster 3553 or BUF634 Used with A4 3 3 E2 E2(f) –VCC NOTE: (1) A4 inverts, see Figure 3. EOUT = (E1 – E2)[1 + (40k/RG)][1/(1 + 2πf 104 –VCC x CF)] NOTE: (1) A4 inverts. See Figure 3. FIGURE 6. Active Low-Pass Filtering. FIGURE 7. Output Power Boosting. to the low values of RG required (RG < 40Ω for (1 + 40k/RG) > 1000). Note, however, that accuracy can degrade due to high amplification of offset, drift, and noise errors. Output offsetting (“zero suppression” or “zero elevation”) may be more easily accomplished with the INA104 than with most other IC instrumentation amplifiers as shown in Figure 4. The use of the extra internal op amp, A4, means that CMR of the instrumentation amp is not disturbed, and that a convenient value of variable resistor can be used. The circuit shown in Figure 2 can also be used to achieve the desired offsetting by scaling the resistors R1 and R2. A low impedance path from pin 6 to Common should be provided to achieve the high CMR specified. Resistance above 0.1Ω will cause the CMR to fall below 106dB. Amplifier A4 also allows active low-pass filtering to be implemented conveniently with a single capacitor. Filtering can be used for noise reduction or band-limiting of the output signal as shown in Figure 6. The common-mode voltage from the 26kΩ resistors in the input section appears at pin 4. Figure 5 shows how this voltage can be used to drive the shield of the input cable. Since the cable is driven at the common-mode voltage, the effects of distributed capacitance is reduced and the AC system common-mode rejection may be improved. Amplifier A4 buffers the CMV at pin 4 from the input cable. Some typical application circuits are shown in Figures 9 through 11. ® 9 INA104 GENERAL RECOMMENDED HANDLING PROCEDURES FOR INTEGRATED CIRCUITS All semiconductor devices are vulnerable, in varying degrees, to damage from the discharge of electrostatic energy. Such damaging can cause performance degradation or failure, either immediate or latent. As a general practice, we recommend the following handling procedures to reduce the risk of electrostatic damage. 2. Ground all operators, equipment, and work stations. 3. Transport and ship microcircuits, or products incorporating microcircuits, in static-free, shielded containers. 4. Connect together all leads of each device by means of a conductive material, when the device is not connected into a circuit. 1. Remove static-generating materials, such as untested plastics, from all areas that handle microcircuits. 5. Control relative humidity to as high a value as practical (50% is recommended). +VCC V Optional Offset Adjust 100kΩ 13 R Transducer or Sensor Shield Resistance Bridge E2 17 R R E1 R –In 15 18 EO = [1 + (40k/RG)] (E2 – E1) 16 14 ∆E 8 INA104 RG IN + EOUT – 5 1 6 2 +In 3 –VCC FIGURE 8. Amplification of a Differential Voltage From a Resistance Bridge. +VCC 13 17 Noise (60Hz Hum) Shield E –In 18 1 14 9 Transducer or Analog Signal INA104 RG 5 10 6 Transformer 2 (1) –VCC FIGURE 9. Amplification of a Transformer Coupled Analog Signal. ® INA104 +In 3 NOTE: (1) Guard drive could be used to improve circuit AC CMR. See Figure 5. 10 EOUT1 7 1 E 2 Noise (60Hz Hum) 8 11 EOUT2 +15V (from isolated power supply with bypassing) 13 High voltage protection diodes are IN459. +15V 17 E1 330kΩ G = 1000 –In 18 INA104 14 +15V LA RG 40.04Ω 1mVp-p RA 330kΩ –15V 8 5 1 RL –15V 1MΩ EOUT 1Vp-p 6 CMV Sense 7 3 To isolation stage 4 2 +In E2 5kΩ (1) 12 10 –15V (from isolated 1MΩ - 10MΩ power supply with bypassing) NOTE: (1) Internal Op Amp, A4, or External Amp (OPA27 or equivalent). Right Leg Driver Amp gives higher AC CMR. FIGURE 10. ECG Amplifier or Recorder Pre-Amp for Biological Signals. 17 –In Isolation Amplifier 18 14 ∆EIN 8 INA104 RG 11 5 10 7 1 2 ISO100, 3650, or 3656(1) EOUT 3 6 +In 13 –15V(2) +15V(2) Input Common +15V Isolated Power Supply 722 +15V Output Common –15V NOTES: (1) Does not require an external ISO P/S. (2) Bypass as shown in Figure 1. FIGURE 11. Precision Isolated Instrumentation Amplifier. ® 11 INA104