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| a FEATURES High DC Precision 75 V max Offset Voltage 1 V/ C max Offset Voltage Drift 150 pA max Input Bias Current 0.2 pA/ C typical IB Drift Low Noise 0.5 V p-p typical Noise, 0.1 Hz to 10 Hz Low Power 600 A max Supply Current per Amplifier Chips & MIL-STD-883B Processing Available Available in Tape and Reel in Accordance with EIA-481A Standard Single Version: AD705, Dual Version: AD706 PRIMARY APPLICATIONS Industrial/Process Controls Weigh Scales ECG/EKG Instrumentation Low Frequency Active Filters Quad Picoampere Input Current Bipolar Op Amp AD704 CONNECTION DIAGRAMS 14-Pin Plastic DIP (N) 14-Pin Cerdip (Q) Packages OUTPUT -IN + IN +VS + IN -IN OUTPUT 1 2 3 4 5 6 7 2 3 1 4 14 13 12 OUTPUT -IN + IN -VS + IN -IN OUTPUT OUTPUT -IN + IN +V S + IN -IN OUTPUT NC 1 2 3 4 5 6 7 8 NC = NO CONNECT 2 3 1 4 16-Pin SOIC (R) Package 16 15 14 OUTPUT -IN + IN -VS + IN -IN OUTPUT NC AD704 (TOP VIEW) 11 10 9 8 AD704 (TOP VIEW) 13 12 11 10 9 (E) Package 20-Terminal LCC OUT1 OUT4 -IN1 NC -IN4 3 2 1 20 19 PRODUCT DESCRIPTION The AD704 is a quad, low power bipolar op amp that has the low input bias current of a BiFET amplifier but which offers a significantly lower IB drift over temperature. It utilizes Superbeta bipolar input transistors to achieve picoampere input bias current levels (similar to FET input amplifiers at room temperature), while its IB typically only increases by 5x at +125C (unlike a BiFET amp, for which IB doubles every 10C resulting in a 1000x increase at +125C). Furthermore the AD704 achieves 75 V offset voltage and low noise characteristics of a precision bipolar input op amp. 100 +IN1 4 NC 5 +VS 6 NC 7 +IN2 8 AMP 1 AMP 4 18 +IN4 17 NC 16 -VS 15 NC 14 +IN3 AD704 AMP 2 AMP 3 9 -IN2 10 OUT2 11 NC 12 OUT3 13 -IN3 NC = NO CONNECT 10 TYPICAL I B - nA TYPICAL JFET AMP 1 Since it has only 1/20 the input bias current of an AD OP07, the AD704 does not require the commonly used "balancing" resistor. Furthermore, the current noise is 1/5 that of the AD OP07 which makes the AD704 usable with much higher source impedances. At 1/6 the supply current (per amplifier) of the AD OP07, the AD704 is better suited for today's higher density circuit boards and battery powered applications. The AD704 is an excellent choice for use in low frequency active filters in 12- and 14-bit data acquisition systems, in precision instrumentation, and as a high quality integrator. The AD704 is internally compensated for unity gain and is available in five performance grades. The AD704J and AD704K are rated over the commercial temperature range of 0C to +70C. The AD704A and AD704B are rated over the industrial temperature of -40C to +85C. The AD704T is rated over the military temperature range of -55C to +125C and is available processed to MIL-STD-883B, Rev. C. 0.1 AD704T 0.01 -55 +25 TEMPERATURE - C +125 Figure 1. Input Bias Current Over Temperature REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703 AD704-SPECIFICATIONS (@ T = +25 C, V A CM = 0 V, and 15 V dc, unless otherwise noted) AD704K/B Min Typ Max 30 50 0.2 132 126 0.3 80 0.2 75 150 1.0 112 108 150 200 200 300 30 0.4 80 80 100 150 200 300 130 200 300 400 110 104 110 106 104 104 110 106 150 150 50 0.4 80 100 Min AD704T Typ Max 30 80 132 126 0.3 80 1.0 600 700 150 200 400 500 150 250 400 600 200 250 100 150 1.0 Units V V V/C dB dB V/month pA pA pA/C pA pA pA pA pA/C pA pA V V pA pA dB dB dB dB dB Model Conditions INPUT OFFSET VOLTAGE Initial Offset Offset vs. Temp, Average TC vs. Supply (PSRR) TMIN -TMAX Long Term Stability INPUT BIAS CURRENT 1 vs. Temp, Average TC TMIN -TMAX TMIN -TMAX INPUT OFFSET CURRENT vs. Temp, Average TC TMIN -TMAX TMIN -TMAX MATCHING CHARACTERISTICS Offset Voltage TMIN -TMAX Input Bias Current2 TMIN -TMAX Common-Mode Rejection 3 TMIN -TMAX Power Supply Rejection 4 Crosstalk5 FREQUENCY RESPONSE UNITY GAIN Crossover Frequency Slew Rate, Unity Gain Slew Rate INPUT IMPEDANCE Differential Common-Mode INPUT VOLTAGE RANGE Common-Mode Voltage Common-Mode Rejection Ratio INPUT CURRENT NOISE INPUT VOLTAGE NOISE TMIN -TMAX f = 10 Hz RLOAD = 2 k AD704J/A Min Typ Max 50 100 0.2 132 126 0.3 100 0.3 150 250 1.5 TMIN -TMAX 100 VS = 2 to 18 V VS = 2.5 to 18 V 100 VCM = 0 V VCM = 13.5 V VCM = 0 V VCM = 13.5 V VCM = 0 V VCM = 13.5 V VCM = 0 V VCM = 13.5 V 112 108 270 300 300 400 80 0.6 100 100 250 300 300 400 250 400 500 600 94 94 94 94 150 G = -1 TMIN -TMAX 0.8 0.15 0.1 40 2 300 2 13.5 14 100 132 98 128 3 50 0.5 17 15 200 150 200 150 2000 1500 1000 1000 0.8 0.15 0.1 40 2 300 2 13.5 14 114 132 108 128 3 50 0.5 17 15 400 300 300 200 2000 1500 1000 1000 2.0 22 400 300 200 100 0.8 0.15 0.1 40 2 300 2 13.5 14 110 132 108 128 3 50 0.5 17 15 2000 1500 1000 1000 2.0 22 MHz V/s V/s M pF G pF V dB dB pA p-p fA/Hz V p-p nV/Hz nV/Hz V/mV V/mV V/mV V/mV VCM = 13.5 V TMIN -TMAX 0.1 to 10 Hz f = 10 Hz 0.1 to 10 Hz f = 10 Hz f = 1 kHz VO = 12 V RLOAD = 10 k TMIN -TMAX VO = 10 V RLOAD = 2 k TMIN -TMAX 22 OPEN-LOOP GAIN -2- REV. A AD704 Model Conditions OUTPUT CHARACTERISTICS Voltage Swing Current CAPACITIVE LOAD Drive Capability POWER SUPPLY Rated Performance Operating Range Quiescent Current TMIN -TMAX TRANSISTOR COUNT # of Transistors RLOAD = 10 k TMIN -TMAX Short Circuit Gain = + 1 AD704J/A Min Typ Max AD704K/B Min Typ Max Min AD704T Typ Max Units 13 14 15 10,000 15 1.5 1.6 180 13 14 15 10,000 15 1.5 1.6 180 13 14 15 10,000 15 1.5 1.6 180 V mA pF V V mA mA 2.0 18 2.4 2.6 2.0 18 2.4 2.6 2.0 18 2.4 2.6 NOTES 1 Bias current specifications are guaranteed maximum at either input. 2 Input bias current match is the maximum difference between corresponding inputs of all four amplifiers. 3 CMRR match is the difference of VOS/VCM between any two amplifiers, expressed in dB. 4 PSRR match is the difference between VOS/VSUPPLY for any two amplifiers, expressed in dB. 5 See Figure 2a for test circuit. All min and max specifications are guaranteed. Specifications subject to change without notice. ABSOLUTE MAXIMUM RATINGS 1 METALIZATION PHOTOGRAPH Dimensions shown in inches and (mm). Contact factory for latest dimensions. Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V Internal Power Dissipation (+25C) . . . . . . . . . . . See Note 2 Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VS Differential Input Voltage3 . . . . . . . . . . . . . . . . . . . . . . . 0.7 V Output Short Circuit Duration (Single Input) . . . . . Indefinite Storage Temperature Range (Q) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65C to +150C (N, R) . . . . . . . . . . . . . . . . . . . . . . . . . . . -65C to +125C Operating Temperature Range AD704J/K . . . . . . . . . . . . . . . . . . . . . . . . . . . 0C to +70C AD704A/B . . . . . . . . . . . . . . . . . . . . . . . . . -40C to +85C AD704T . . . . . . . . . . . . . . . . . . . . . . . . . . -55C to +125C Lead Temperature Range (Soldering 10 seconds) . . . . +300C NOTES 1 Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2 Specification is for device in free air: 14-Pin Plastic Package: JA = 150C/Watt 14-Pin Cerdip Package: JA = 110C/Watt 16-Pin SOIC Package: JA = 100C/Watt 20-Terminal LCC Package: JA = 150C/Watt 3 The input pins of this amplifier are protected by back-to-back diodes. If the differential voltage exceeds 0.7 volts, external series protection resistors should be added to limit the input current to less than 25 mA. 9k 1k -80 AMP4 -100 CROSSTALK - dB AMP2 AMP3 -120 INPUT * SIGNAL 1k 1/4 AD704 OUTPUT +V S 2.5k 0.1 F COM 0.1 F -V S 1F 1F AD704 PIN 4 -140 AD704 PIN 11 -160 10 100 1k FREQUENCY - Hz 10k 100k ALL 4 AMPLIFIERS ARE CONNECTED AS SHOWN INPUT (SUCH THAT AMPLIFIER'S OUTPUT IS AT MAX *THE SIGNAL WITHOUT CLIPPING THESLEW LIMITING) IS APPLIED TO ONE AMPLITUDE OR AMPLIFIER AT A TIME. THE OUTPUTS OF THE OTHER THREE AMPLIFIERS ARE THEN MEASURED FOR CROSSTALK. Figure 2b. Crosstalk vs. Frequency Figure 2a. Crosstalk Test Circuit REV. A -3- AD704-Typical Characteristics (@ +25 C, V = S 15 V, unless otherwise noted) ORDERING GUIDE Model AD704JN AD704JR AD704JR-/REEL AD704KN AD704AN AD704AQ AD704AR AD704AR-REEL AD704BQ AD704SE/883B AD704TQ AD704TQ/883B Temperature Range 0C to +70C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -55C to +125C -55C to +125C -55C to +125C Package Option* N-14 R-16 Tape and Reel N-14 N-14 Q-14 R-16 Tape and Reel Q-14 E-20A Q-14 Q-14 Chips are also available. *E = Leadless Ceramic Chip Carrier; N = Plastic DIP; Q = Cerdip; R = Small Outline (SOIC). 50 50 50 PERCENTAGE OF UNITS PERCENTAGE OF UNITS 30 30 PERCENTAGE OF UNITS -80 +160 40 40 40 30 20 20 20 10 10 10 0 -80 -40 0 +40 +80 INPUT OFFSET VOLTAGE - V 0 -160 0 +80 INPUT BIAS CURRENT - pA 0 -120 -60 0 +60 +120 INPUT OFFSET CURRENT - pA Figure 3. Typical Distribution of Input Offset Voltage Figure 4. Typical Distribution of Input Bias Current Figure 5. Typical Distribution of Input Offset Current INPUT COMMON-MODE VOLTAGE LIMIT - Volts (REFERRED TO SUPPLY VOLTAGES) +V S -0.5 -1.0 -1.5 35 30 25 20 15 10 5 0 100 OFFSET VOLTAGE DRIFT - V/C OUTPUT VOLTAGE - Volts p-p SOURCE RESISTANCE MAY BE EITHER BALANCED OR UNBALANCED 10 +1.5 +1.0 +0.5 -VS 0 5 10 15 20 SUPPLY VOLTAGE - Volts 1.0 0.1 1k 10k 100k FREQUENCY - Hz 1M 1k 10k 100k 1M 10M 100M SOURCE RESISTANCE - Figure 6. Input Common-Mode Voltage Range vs. Supply Voltage Figure 7. Large Signal Frequency Response Figure 8. Offset Voltage Drift vs. Source Resistance -4- REV. A AD704 50 CHANGE IN OFFSET VOLTAGE - V 4 120 100 3 INPUT BIAS CURRENT - pA PERCENTAGE OF UNITS 40 80 POSITIVE I B 60 30 2 20 40 NEGATIVE I B 20 1 10 0 -0.8 -0.4 0 +0.4 +0.8 INPUT OFFSET VOLTAGE DRIFT - V/C 0 0 1 2 3 4 5 WARM-UP TIME - Minutes 0 -15 -10 -5 0 5 10 15 COMMON MODE VOLTAGE - Volts Figure 9. Typical Distribution of Offset Voltage Drift Figure 10. Change in Input Offset Voltage vs. Warm-Up Time Figure 11. Input Bias Current vs. Common-Mode Voltage 1000 1000 VOLTAGE NOISE - nV/ Hz CURRENT NOISE - fA/ 100 Hz 100 10 10 100 20M 10k VOUT 1 1 10 100 FREQUENCY - Hz 1000 1 1 10 100 1000 FREQUENCY - Hz Figure 12. Input Noise Voltage Spectral Density Figure 13. Input Noise Current Spectral Density Figure 14. 0.1 Hz to 10 Hz Noise Voltage 500 +160 +140 180 160 V S = 15V T A = +25C QUIESCENT CURRENT - A 450 FIGURE 15 CMR - dB +120 VS = 15V +100 +80 +60 +40 140 120 100 -PSR 80 +PSR 60 40 400 +125C +25C 350 -55C 300 0 5 10 15 20 +20 0 0.1 PSR - dB 1 10 100 1k 10k FREQUENCY - Hz 100k 1M 20 0.1 1 10 SUPPLY VOLTAGE - Volts 100 1k 10k FREQUENCY - Hz 100k 1M Figure 15. Quiescent Supply Current vs. Supply Voltage (per Amplifier) Figure 16. Common-Mode Rejection vs. Frequency Figure 17. Power Supply Rejection vs. Frequency REV. A -5- AD704 10M 140 0 30 60 PHASE 80 60 40 GAIN 20 0 180 90 120 150 OUTPUT VOLTAGE SWING - Volts (REFERRED TO SUPPLY VOLTAGES) +VS -0.5 -1.0 -1.5 R L= 10k OPEN-LOOP VOLTAGE GAIN - dB 120 100 OPEN-LOOP VOLTAGE GAIN +25 C 1M +125 C PHASE SHIFT - Degrees -55 C +1.5 +1.0 +0.5 -VS 0 5 15 10 SUPPLY VOLTAGE - Volts 20 100k 1 -20 2 4 6 8 10 LOAD RESISTANCE - k 100 0.01 0.1 1 10 100 1k 10k 100k 1M 10M FREQUENCY - Hz Figure 18. Open-Loop Gain vs. Load Resistance Over Temperature Figure 19. Open-Loop Gain and Phase vs. Frequency Figure 20. Output Voltage Swing vs. Supply Voltage CLOSED-LOOP OUTPUT IMPEDANCE - Ohms 1000 RF +VS 0.1 F 100 90 100 10 A V = -1000 1 A V = +1 0.1 1/4 AD704 V IN 0.1 F RL 2k CL V OUT 10 0% 0.01 I OUT = +1mA 0.001 1 10 100 1k FREQUENCY - Hz 10k 100k SQUARE WAVE INPUT -VS 2V 50s Figure 21. Closed-Loop Output Impedance vs. Frequency Figure 22a. Unity Gain Follower (For Large Signal Applications, Resistor RF Limits the Current Through the Input Protection Diodes) 5s 100 90 Figure 22b. Unity Gain Follower Large Signal Pulse Response RF = 10 k, CL = 1,000 pF 10k 5s 100 90 +V S 0.1 F 10k V IN 1/4 AD704 RL 2.5k VOUT CL 10 0% 10 0% SQUARE WAVE INPUT 0.1 F 20mV 20mV -VS Figure 22c. Unity Gain Follower Small Signal Pulse Response RF = 0 , CL = 100 pF Figure 22d. Unity Gain Follower Small Signal Pulse Response RF = 0 , CL = 1,000 pF Figure 23a. Unity Gain Inverter Connection -6- REV. A AD704 2V 100 90 50s 100 90 5S 100 90 5S 10 0% 10 0% 10 0% 20mV 20mV Figure 23b. Unity Gain Inverter Large Signal Pulse Response, CL = 1,000 pF Figure 23c. Unity Gain Inverter Small Signal Pulse Response, CL = 100 pF C1 4C2 1 _________ R6 __ C1C2 Figure 23d. Unity Gain Inverter Small Signal Pulse Response, CL = 1,000 pF 49.9k R2 Q2 = = 2.4k R5 47.5k R4 Ct 6.34k R3 +VS RG 6.34k R1 R6 = R7 1 = _________ R8 C3C4 R8 = R9 1M R6 1M R7 C2 0.1 F -VS R10 C5 2M 0.01F C1 1M R8 1M R9 C4 C3 OUTPUT 0.1 F 1/4 AD704 DC CMRR TRIM (5k POT) -V IN +VIN 1/4 AD704 1/4 AD704 1/4 AD704 R2 2R2 __ ___ INSTRUMENTATION AMPLIFIER GAIN = 1 + + (FOR R1 = R3, R2 = R4 + R5) R1 RG ALL RESISTORS METAL FILM, 1% R11 C6 OPTIONAL BALANCE RESISTOR NETWORKS CAN BE REPLACED WITH A SHORT CAPACITORS C2 AND C4 ARE SOUTHERN ELECTRONICS MPCC, POLYCARBONATE, 5%, 50 VOLT Figure 24. Gain of 10 Instrumentation Amplifier with Post Filtering The instrumentation amplifier with post filtering (Figure 24) combines two applications which benefit greatly from the AD704. This circuit achieves low power and dc precision over temperature with a minimum of components. The instrumentation amplifier circuit offers many performance benefits including BiFET level input bias currents, low input offset voltage drift and only 1.2 mA quiescent current. It will operate for gains G 2, and at lower gains it will benefit from the fact that there is no output amplifier offset and noise contribution as encountered in a 3 op amp design. Good low frequency CMRR is achieved even without the optional AC CMRR trim (Figure 25). Table I provides resistance values for 3 common circuit gains. For other gains, use the following equations: R2 = R4 + R5 = 49.9 k 49.9 k R1 = R3 = 0.9 G - 1 Table I. Resistance Values for Various Gains Circuit Gain (G) RG (Max Value of Trim Potentiometer) Bandwidth (-3 dB), Hz R1 & R3 10 100 1,000 160 6.34 k 526 56.2 166 k 16.6 k 1.66 k GAIN = 10, 0.2V p-p COMMON-MODE INPUT COMMON MODE REJECTION - dB 140 120 100 80 TYPICAL MONOLITHIC IN AMP CIRCUIT TRIMMED USING CAPACITOR C t 60 40 WITHOUT CAPACITOR C t 20 0 1 10 100 FREQUENCY - Hz 1k 10k Max Value of RG = Ct 99.8 k 0.06 G 1 2 (R3) 5 x 105 Figure 25. Common-Mode Rejection vs. Frequency with and without Capacitor Ct REV. A -7- __ OPTIONAL AC CMRR TRIM GAIN TRIM (500k POT) Q1 = C3 4C4 2M 0.01F 50k 5k 0.5k AD704 The 1 Hz, 4-pole active filter offers dc precision with a minimum of components and cost. The low current noise, IOS, and IB allow the use of 1 M resistors without sacrificing the 1 V/C drift of the AD704. This means lower capacitor values may be used, reducing cost and space. Furthermore, since the AD704's IB is as low as its IOS, over most of the MIL temperature range, most applications do not require the use of the normal balancing resistor (with its stability capacitor). Adding the optional balancing resistor enhances performance at high temperatures, as shown in Figure 26. Table II gives capacitor values for several common low pass responses. 180 120 OFFSET VOLTAGE OF FILTER CIRCUIT (RTI) - V WITHOUT OPTIONAL BALANCE RESISTOR, R3 60 0 -60 -120 -180 -40 0 +40 +80 o TEMPERATURE - C +120 Figure 26. VOS vs. Temperature Performance of the 1 Hz Filter Circuit Table II. 1 Hz, 4-Pole Low-Pass Filter Recommended Component Values Desired Low Pass Response Bessel Butterworth 0.1 dB Chebychev 0.2 dB Chebychev 0.5 dB Chebychev 1.0 dB Chebychev Section 1 Frequency (Hz) 1.43 1.00 0.648 0.603 0.540 0.492 Q 0.522 0.541 0.619 0.646 0.705 0.785 Section 2 Frequency (Hz) 1.60 1.00 0.948 0.941 0.932 0.925 Q 0.806 1.31 2.18 2.44 2.94 3.56 C1 ( F) 0.116 0.172 0.304 0.341 0.416 0.508 C2 ( F) 0.107 0.147 0.198 0.204 0.209 0.206 C3 ( F) 0.160 0.416 0.733 0.823 1.00 1.23 C4 ( F) 0.0616 0.0609 0.0385 0.0347 0.0290 0.0242 Specified Values are for a -3 dB point of 1.0 Hz. For other frequencies simply scale capacitors C1 through C4 directly; i.e., for 3 Hz Bessel response, C1 = 0.0387 F, C2 = 0.0357 F, C3 = 0.0533 F, C4 = 0.0205 F. OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 14-Pin Cerdip (Q) Package 14-Pin Plastic DIP (N) Package 16-Pin Plastic SO (R) Package 20-Terminal LCCC (E) Package 0.100 (2.54) 0.064 (1.63) 0.358 (9.09) 0.342 (8.69) 0.040 (1.02) x 45 REF 3 PLCS NO. 1 PIN INDEX 0.050 (1.27) BSC 0.028 (0.71) 0.022 (0.56) 0.020 (0.51) x 45 REF -8- REV. A PRINTED IN U.S.A. C1476-24-10/90 WITH OPTIONAL BALANCE RESISTOR, R3 |
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