a Quad Picoampere Input Current Bipolar Op Amp AD704 FEATURES High DC Precision 75 mV max Offset Voltage 1 mV/8C max Offset Voltage Drift 150 pA max Input Bias Current 0.2 pA/8C typical IB Drift Low Noise 0.5 mV p-p typical Noise, 0.1 Hz to 10 Hz Low Power 600 mA 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 CONNECTION DIAGRAMS 14-Pin Plastic DIP (N) 14-Pin Cerdip (Q) Packages OUTPUT 1 –IN 2 + IN 3 +VS 4 14 1 4 AD704 16-Pin SOIC (R) Package OUTPUT OUTPUT 1 13 –IN –IN 2 12 + IN + IN 3 11 –V S +V S 4 5 –IN 6 OUTPUT 7 2 4 AD704 15 –IN 14 + IN 13 –V S 12 + IN 11 –IN 10 + IN + IN 5 9 –IN –IN 6 8 OUTPUT OUTPUT 7 10 NC 8 9 3 PRIMARY APPLICATIONS Industrial/Process Controls Weigh Scales ECG/EKG Instrumentation Low Frequency Active Filters 1 OUTPUT (TOP VIEW) (TOP VIEW) + IN 16 2 3 OUTPUT NC NC = NO CONNECT –IN1 OUT1 NC OUT4 –IN4 (E) Package 20-Terminal LCC 3 2 1 20 19 PRODUCT DESCRIPTION 100 TYPICAL I B – nA TYPICAL JFET AMP 1 0.1 AD704T +25 18 +IN4 NC 5 AMP 1 +VS 6 NC 7 17 NC AMP 4 16 –VS AD704 AMP 2 AMP 3 15 NC +IN2 8 9 10 11 12 13 OUT2 NC OUT3 –IN3 14 +IN3 NC = NO CONNECT 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. 10 0.01 –55 +IN1 4 –IN2 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 5× at +125°C (unlike a BiFET amp, for which IB doubles every 10°C resulting in a 1000× increase at +125°C). Furthermore the AD704 achieves 75 µV offset voltage and low noise characteristics of a precision bipolar input op amp. +125 TEMPERATURE – °C Figure 1. Input Bias Current Over Temperature 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 0°C to +70°C. The AD704A and AD704B are rated over the industrial temperature of –40°C to +85°C. The AD704T is rated over the military temperature range of –55°C to +125°C and is available processed to MIL-STD-883B, Rev. C. 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 = +258C, V A 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 CM = 0 V, and 615 V dc, unless otherwise noted) AD704J/A Min Typ Max AD704K/B Min Typ Max 50 100 0.2 132 126 0.3 150 250 1.5 30 50 0.2 132 126 0.3 75 150 1.0 100 270 300 80 150 200 TMIN –TMAX 100 VS = ± 2 to ± 18 V VS = ± 2.5 to ± 18 V 100 VCM = 0 V VCM = ± 13.5 V 0.3 VCM = 0 V VCM = ± 13.5 V VCM = 0 V VCM = ± 13.5 V 80 0.6 100 100 VCM = 0 V VCM = ± 13.5 V Input Bias Current2 TMIN –TMAX Common-Mode Rejection 3 TMIN –TMAX Power Supply Rejection 4 FREQUENCY RESPONSE UNITY GAIN Crossover Frequency Slew Rate, Unity Gain Slew Rate TMIN –TMAX f = 10 Hz RLOAD = 2 kΩ INPUT IMPEDANCE Differential Common-Mode INPUT VOLTAGE RANGE Common-Mode Voltage Common-Mode Rejection Ratio VCM = ± 13.5 V TMIN –TMAX 250 300 30 0.4 80 80 300 400 94 94 94 94 G = –1 TMIN –TMAX µV µV µV/°C dB dB µV/month 200 250 pA pA pA/°C pA pA 1.0 600 700 100 150 50 0.4 80 100 200 300 110 104 110 106 150 200 400 500 150 250 400 600 104 104 110 106 pA pA pA/°C pA pA µV µV pA pA dB dB dB dB 150 150 150 dB 0.8 0.15 0.1 0.8 0.15 0.1 0.8 0.15 0.1 MHz V/µs V/µs 40i2 300i2 40i2 300i2 40i2 300i2 MΩipF GΩipF ± 13.5 ± 14 100 132 98 128 ± 13.5 ± 14 114 132 108 128 0.1 to 10 Hz f = 10 Hz 3 50 3 50 INPUT VOLTAGE NOISE 0.1 to 10 Hz f = 10 Hz f = 1 kHz 0.5 17 15 0.5 17 15 VO = ± 12 V RLOAD = 10 kΩ TMIN –TMAX VO = ± 10 V RLOAD = 2 kΩ TMIN –TMAX 80 Units 100 150 1.0 132 126 0.3 130 200 300 400 INPUT CURRENT NOISE OPEN-LOOP GAIN 112 108 200 300 250 400 500 600 TMIN –TMAX AD704T Typ Max 30 80 0.2 300 400 MATCHING CHARACTERISTICS Offset Voltage Crosstalk5 112 108 Min 22 ± 13.5 ± 14 110 132 108 128 V dB dB 3 50 2.0 0.5 17 15 22 pA p-p fA/√Hz 2.0 22 µV p-p nV/√Hz nV/√Hz 200 150 2000 1500 400 300 2000 1500 400 300 2000 1500 V/mV V/mV 200 150 1000 1000 300 200 1000 1000 200 100 1000 1000 V/mV V/mV –2– REV. A AD704 Model Conditions OUTPUT CHARACTERISTICS Voltage Swing RLOAD = 10 kΩ TMIN –TMAX Short Circuit Current CAPACITIVE LOAD Drive Capability AD704J/A Min Typ Max AD704K/B Min Typ Max Min ± 13 ± 13 ± 13 Gain = + 1 10,000 POWER SUPPLY Rated Performance Operating Range Quiescent Current ± 2.0 TRANSISTOR COUNT ± 14 ± 15 ± 15 TMIN –TMAX 1.5 1.6 # of Transistors 180 ± 14 ± 15 AD704T Typ Max 10,000 ± 18 2.4 2.6 ± 2.0 ± 15 1.5 1.6 ± 18 2.4 2.6 ± 2.0 ± 14 ± 15 V mA 10,000 pF ± 15 1.5 1.6 180 ± 18 2.4 2.6 180 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 Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 18 V Internal Power Dissipation (+25°C) . . . . . . . . . . . See Note 2 Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± VS Differential Input Voltage3 . . . . . . . . . . . . . . . . . . . . . . . ± 0.7 V Output Short Circuit Duration (Single Input) . . . . . Indefinite Storage Temperature Range (Q) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to +150°C (N, R) . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to +125°C Operating Temperature Range AD704J/K . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C AD704A/B . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to +85°C AD704T . . . . . . . . . . . . . . . . . . . . . . . . . . –55°C to +125°C Lead Temperature Range (Soldering 10 seconds) . . . . +300°C Dimensions shown in inches and (mm). Contact factory for latest dimensions. 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: θJA = 150°C/Watt 14-Pin Cerdip Package: θJA = 110°C/Watt 16-Pin SOIC Package: θJA = 100°C/Watt 20-Terminal LCC Package: θJA = 150°C/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. –80 AMP4 CROSSTALK – dB –100 9k Ω 1k Ω 1/4 AD704 INPUT * SIGNAL OUTPUT AD704 PIN 4 +V S 2.5k Ω 1k Ω 0.1 µF COM 0.1 µF AMP3 –120 –140 1µF –160 AD704 PIN 11 10 100 1k 10k 100k FREQUENCY – Hz ALL 4 AMPLIFIERS ARE CONNECTED AS SHOWN SIGNAL INPUT (SUCH THAT THE AMPLIFIER'S OUTPUT IS AT MAX *THE AMPLITUDE WITHOUT CLIPPING OR SLEW LIMITING) IS APPLIED TO ONE Figure 2b. Crosstalk vs. Frequency AMPLIFIER AT A TIME. THE OUTPUTS OF THE OTHER THREE AMPLIFIERS ARE THEN MEASURED FOR CROSSTALK. Figure 2a. Crosstalk Test Circuit REV. A AMP2 1µF –V S –3– Units V V mA mA AD704–Typical Characteristics (@ +258C, V = 615 V, unless otherwise noted) S ORDERING GUIDE Model Temperature Range Package Option* AD704JN AD704JR AD704JR-/REEL AD704KN AD704AN AD704AQ AD704AR AD704AR-REEL AD704BQ AD704SE/883B AD704TQ AD704TQ/883B 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –55°C to +125°C –55°C to +125°C –55°C to +125°C 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 50 50 40 40 40 30 20 10 30 20 10 0 30 20 10 0 –80 –40 0 +80 +40 0 –160 INPUT OFFSET VOLTAGE – µV –80 0 +80 +160 –120 Figure 4. Typical Distribution of Input Bias Current –1.0 –1.5 +1.5 +1.0 +0.5 30 25 20 15 10 5 0 –VS 0 5 10 15 20 SUPPLY VOLTAGE – Volts Figure 6. Input Common-Mode Voltage Range vs. Supply Voltage +60 +120 100 OFFSET VOLTAGE DRIFT – µV/°C OUTPUT VOLTAGE – Volts p-p –0.5 0 Figure 5. Typical Distribution of Input Offset Current 35 +V S –60 INPUT OFFSET CURRENT – pA INPUT BIAS CURRENT – pA Figure 3. Typical Distribution of Input Offset Voltage INPUT COMMON-MODE VOLTAGE LIMIT – Volts (REFERRED TO SUPPLY VOLTAGES) PERCENTAGE OF UNITS 50 PERCENTAGE OF UNITS PERCENTAGE OF UNITS Chips are also available. *E = Leadless Ceramic Chip Carrier; N = Plastic DIP; Q = Cerdip; R = Small Outline (SOIC). SOURCE RESISTANCE MAY BE EITHER BALANCED OR UNBALANCED 10 1.0 0.1 1k 10k 100k FREQUENCY – Hz 1M Figure 7. Large Signal Frequency Response –4– 1k 10k 100k 1M 10M 100M SOURCE RESISTANCE – Ω Figure 8. Offset Voltage Drift vs. Source Resistance REV. A AD704 120 4 40 30 20 10 0 100 3 2 1 0 2 3 4 POSITIVE I B 60 40 NEGATIVE I B 20 5 –10 –5 0 10 5 15 COMMON MODE VOLTAGE – Volts WARM-UP TIME – Minutes Figure 9. Typical Distribution of Offset Voltage Drift Figure 11. Input Bias Current vs. Common-Mode Voltage Figure 10. Change in Input Offset Voltage vs. Warm-Up Time 1000 Hz 1000 100 CURRENT NOISE – fA/ 10 100 100Ω 10 10kΩ 20MΩ VOUT 1 1 1 10 100 FREQUENCY – Hz 1 1000 Figure 12. Input Noise Voltage Spectral Density 1000 FIGURE 15 +160 180 +140 160 +120 140 CMR – dB VS = ± 15V 400 +125°C +100 +80 +60 –55°C 5 10 15 20 SUPPLY VOLTAGE – ±Volts Figure 15. Quiescent Supply Current vs. Supply Voltage (per Amplifier) REV. A T A = +25°C 120 100 –PSR +PSR 350 0 V S = ±15V 80 +25°C 300 Figure 14. 0.1 Hz to 10 Hz Noise Voltage Figure 13. Input Noise Current Spectral Density 500 450 100 10 FREQUENCY – Hz PSR – dB VOLTAGE NOISE – nV/ Hz 1 80 0 –15 0 –0.8 –0.4 0 +0.4 +0.8 INPUT OFFSET VOLTAGE DRIFT – µV/°C QUIESCENT CURRENT – µA INPUT BIAS CURRENT – pA CHANGE IN OFFSET VOLTAGE – µV PERCENTAGE OF UNITS 50 +40 60 +20 40 0 0.1 1 10 100 1k 10k FREQUENCY – Hz 100k 1M Figure 16. Common-Mode Rejection vs. Frequency –5– 20 0.1 1 10 100 1k 10k FREQUENCY – Hz 100k 1M Figure 17. Power Supply Rejection vs. Frequency AD704 +25 C 1M +125 C 120 30 +VS 60 100 PHASE 80 90 60 120 150 40 GAIN 180 20 0 1 2 4 6 8 10 LOAD RESISTANCE – kΩ 0.01 0.1 100 Figure 18. Open-Loop Gain vs. Load Resistance Over Temperature 1 R L= 10kΩ –0.5 –1.0 –1.5 +1.5 +1.0 +0.5 –VS –20 100k CLOSED-LOOP OUTPUT IMPEDANCE – Ohms 0 OUTPUT VOLTAGE SWING – Volts (REFERRED TO SUPPLY VOLTAGES) –55 C 140 PHASE SHIFT – Degrees OPEN-LOOP VOLTAGE GAIN – dB OPEN-LOOP VOLTAGE GAIN 10M 10 100 1k 10k 100k 1M 10M FREQUENCY – Hz 0 Figure 19. Open-Loop Gain and Phase vs. Frequency 5 15 10 SUPPLY VOLTAGE – ±Volts 20 Figure 20. Output Voltage Swing vs. Supply Voltage RF 1000 +VS 100 0.1 µF 100 90 10 A V = –1000 1/4 AD704 1 V OUT RL 2kΩ V IN A V = +1 CL 0.1 0.1 µF 10 0% SQUARE WAVE INPUT 0.01 I OUT = +1mA 2V –VS 50µs 0.001 1 10 100 1k FREQUENCY – Hz 10k 100k 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) Figure 22b. Unity Gain Follower Large Signal Pulse Response RF = 10 kΩ, CL = 1,000 pF 10kΩ 5µs 5µs +V S 100 90 100 90 0.1 µF 10kΩ V IN 1/4 AD704 VOUT RL 2.5kΩ 10 10 0% 0% 20mV SQUARE WAVE INPUT CL 0.1 µF 20mV –VS Figure 22c. Unity Gain Follower Small Signal Pulse Response RF = 0 Ω, CL = 100 pF Figure 22d. Unity Gain Follower Small Signal Pulse Response RF = 0 Ω, CL = 1,000 pF –6– Figure 23a. Unity Gain Inverter Connection REV. A AD704 5µS 50µs 5µS 100 90 100 90 100 90 10 10 10 0% 0% 0% 20mV Figure 23c. Unity Gain Inverter Small Signal Pulse Response, CL = 100 pF 47.5k R4 Ct DC CMRR TRIM (5k POT) Q1 = GAIN TRIM (500k POT) OPTIONAL AC CMRR TRIM 6.34k R3 +VS RG 6.34k R1 ω 49.9k R2 = Figure 23d. Unity Gain Inverter Small Signal Pulse Response, CL = 1,000 pF C1 4C2 1 _________ __ Figure 23b. Unity Gain Inverter Large Signal Pulse Response, CL = 1,000 pF 2.4k R5 20mV R6 Q2 = ω C1C2 R6 = R7 1 = _________ R8 C3C4 R8 = R9 0.1 µF 1MΩ R6 1/4 AD704 1MΩ R7 C2 1/4 AD704 C1 1MΩ R8 1/4 AD704 C3 1MΩ R9 –VS R10 R2 __ 2R2 INSTRUMENTATION AMPLIFIER GAIN = 1 + + ___ (FOR R1 = R3, R2 = R4 + R5) R1 RG 2MΩ 0.01µF C5 OUTPUT 1/4 AD704 C4 0.1 µF –V IN +VIN C3 4C4 __ 2V R11 C6 2MΩ 0.01µF ALL RESISTORS METAL FILM, 1% 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 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: Table I. Resistance Values for Various Gains Circuit Gain (G) R1 & R3 RG (Max Value of Trim Potentiometer) Bandwidth (–3 dB), Hz 10 100 1,000 6.34 kΩ 526 Ω 56.2 Ω 166 kΩ 16.6 kΩ 1.66 kΩ 50k 5k 0.5k 160 GAIN = 10, 0.2V p-p COMMON-MODE INPUT COMMON MODE REJECTION – dB 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. R2 = R4 + R5 = 49.9 kΩ 49.9 kΩ R1 = R3 = 0.9 G − 1 Max Value of RG = Ct ≈ REV. A 99.8 k 0.06 G 140 CIRCUIT TRIMMED USING CAPACITOR C t 120 100 80 TYPICAL MONOLITHIC IN AMP 60 40 WITHOUT CAPACITOR C t 20 0 1 10 100 FREQUENCY – Hz 1k 10k Figure 25. Common-Mode Rejection vs. Frequency with and without Capacitor Ct 1 2 π (R3) 5 × 105 –7– 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 MΩ resistors without sacrificing the 1 µV/°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. 120 WITHOUT OPTIONAL BALANCE RESISTOR, R3 60 0 WITH OPTIONAL BALANCE RESISTOR, R3 C1476–24–10/90 OFFSET VOLTAGE OF FILTER CIRCUIT (RTI) – µV 180 –60 –120 –180 –40 0 +120 +40 +80 o TEMPERATURE – C 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 Section 1 Frequency (Hz) Bessel Butterworth 0.1 dB Chebychev 0.2 dB Chebychev 0.5 dB Chebychev 1.0 dB Chebychev 1.43 1.00 0.648 0.603 0.540 0.492 Q Section 2 Frequency (Hz) Q C1 (mF) C2 (mF) C3 (mF) C4 (mF) 0.522 0.541 0.619 0.646 0.705 0.785 1.60 1.00 0.948 0.941 0.932 0.925 0.806 1.31 2.18 2.44 2.94 3.56 0.116 0.172 0.304 0.341 0.416 0.508 0.107 0.147 0.198 0.204 0.209 0.206 0.160 0.416 0.733 0.823 1.00 1.23 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 µF, C2 = 0.0357 µF, C3 = 0.0533 µF, C4 = 0.0205 µF. OUTLINE DIMENSIONS 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) NO. 1 PIN INDEX PRINTED IN U.S.A. Dimensions shown in inches and (mm). 0.040 (1.02) x 45° REF 3 PLCS 0.028 (0.71) 0.022 (0.56) 0.050 (1.27) BSC 0.020 (0.51) x 45° REF –8– REV. A