a FEATURES High DC Precision 75 V max Offset Voltage V/ C max Offset Voltage Drift 5 pa max Input Bias Current.2 pa/ C typical I B Drift Low Noise.5 V p-p typical Noise,. Hz to Hz Low Power 6 A max Supply Current per Amplifier Chips & MIL-STD-883B Processing Available Available in Tape and Reel in Accordance with EIA-48A Standard Single Version: AD75, Dual Version: AD76 PRIMARY APPLICATIONS Industrial/Process Controls Weigh Scales ECG/EKG Instrumentation Low Frequency Active Filters PRODUCT DESCRIPTION The 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 I B 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 I B typically only increases by 5 at +25 C (unlike a BiFET amp, for which I B doubles every C resulting in a increase at +25 C). Furthermore the achieves 75 µv offset voltage and low noise characteristics of a precision bipolar input op amp. TYPICAL I na B. TYPICAL JFET AMP. 55 +25 +25 TEMPERATURE C T Figure. Input Bias Current Over Temperature 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. Quad Picoampere Input Current Bipolar Op Amp 4-Pin Plastic DIP (N) 4-Pin Cerdip (Q) Packages 2 4 + IN 3 2 + IN 4 VS (TOP VIEW) + IN 5 + IN 6 2 3 9 7 8 +IN 4 NC 5 6 NC 7 +IN2 8 CONNECTION DIAGRAMS 4 3 6-Pin SOIC (R) Package One Technology Way, P.O. Box 96, Norwood, MA 262-96, U.S.A. Tel: 67/329-47 Fax: 67/326-873 2 4 5 + IN 3 4 + IN 4 3 VS (TOP VIEW) + IN 5 2 + IN NC 6 7 2 3 6 8 9 NC = NO CONNECT (E) Package 2-Terminal LCC 3 2 2 9 9 2 3 2 OUT AMP AMP 2 OUT2 NC NC OUT4 AMP 4 AMP 3 OUT3 4 3 8 +IN4 7 NC 6 5 NC 4 +IN3 NC = NO CONNECT Since it has only /2 the input bias current of an AD OP7, the does not require the commonly used balancing resistor. Furthermore, the current noise is /5 that of the AD OP7 which makes the usable with much higher source impedances. At /6 the supply current (per amplifier) of the AD OP7, the is better suited for today s higher density circuit boards and battery powered applications. The is an excellent choice for use in low frequency active filters in 2- and 4-bit data acquisition systems, in precision instrumentation, and as a high quality integrator. The is internally compensated for unity gain and is available in five performance grades. The J and K are rated over the commercial temperature range of C to +7 C. The A and B are rated over the industrial temperature of 4 C to +85 C. The T is rated over the military temperature range of 55 C to +25 C and is available processed to MIL-STD-883B, Rev. C. NC
SPECIFICATIONS (@ T A = +25 C, V CM = V, and 5 V dc, unless otherwise noted) Model J/A K/B T Conditions Min Typ Max Min Typ Max Min Typ Max Units INPUT OFFSET VOLTAGE Initial Offset 5 5 3 75 3 µv Offset T MIN T MAX 25 5 5 8 5 µv vs. Temp, Average TC.2.5.2.. µv/ C vs. Supply (PSRR) V S = ±2 to ±8 V 32 2 32 2 32 db T MIN T MAX V S = ±2.5 to ±8 V 26 8 26 8 26 db Long Term Stability.3.3.3 µv/month INPUT BIAS CURRENT V CM = V 27 8 5 8 2 pa V CM = ±3.5 V 3 2 25 pa vs. Temp, Average TC.3.2. pa/ C T MIN T MAX V CM = V 3 2 6 pa T MIN T MAX V CM = ±3.5 V 4 3 7 pa INPUT OFFSET CURRENT V CM = V 8 25 3 5 5 pa V CM = ±3.5 V 3 5 2 pa vs. Temp, Average TC.6.4.4 pa/ C T MIN T MAX V CM = V 3 8 2 8 4 pa T MIN T MAX V CM = ±3.5 V 4 8 3 5 pa MATCHING CHARACTERISTICS Offset Voltage 25 3 5 µv T MIN T MAX 4 2 25 µv Input Bias Current 2 5 3 4 pa T MIN T MAX 6 4 6 pa Common-Mode Rejection 3 94 4 db T MIN T MAX 94 4 4 db Power Supply Rejection 4 94 db T MIN T MAX 94 6 6 db Crosstalk 5 f = Hz R LOAD = 2 kω 5 5 5 db FREQUENCY RESPONSE UNITY GAIN Crossover Frequency.8.8.8 MHz Slew Rate, Unity Gain G =.5.5.5 V/µs Slew Rate T MIN T MAX... V/µs INPUT IMPEDANCE Differential 4 2 4 2 4 2 MΩ pf Common-Mode 3 2 3 2 3 2 GΩ pf INPUT VOLTAGE RANGE Common-Mode Voltage ±3.5 ±4 ±3.5 ±4 ±3.5 ±4 V Common-Mode Rejection Ratio V CM = ±3.5 V 32 4 32 32 db T MIN T MAX 98 28 8 28 8 28 db INPUT CURRENT NOISE. to Hz 3 3 3 pa p-p f = Hz 5 5 5 fa/ Hz INPUT VOLTAGE NOISE. to Hz.5.5 2..5 2. µv p-p f = Hz 7 7 7 nv/ Hz f = khz 5 22 5 22 5 22 nv/ Hz OPEN-LOOP GAIN V O = ±2 V R LOAD = kω 2 2 4 2 4 2 V/mV T MIN T MAX 5 5 3 5 3 5 V/mV V O = ± V R LOAD = 2 kω 2 3 2 V/mV T MIN T MAX 5 2 V/mV 2
CROSSTALK db METALIZATION PHOTOGRAPH Dimensions shown in inches and (mm). Contact factory for latest dimensions. 8 2 4 AMP2 AMP4 AMP3 6 k k k Figure 2b. Crosstalk vs. Frequency Model J/A K/B T Conditions Min Typ Max Min Typ Max Min Typ Max Units CHARACTERISTICS Voltage Swing R LOAD = kω T MIN T MAX ±3 ±4 ± 3 ±4 ±3 ±4 V Current Short Circuit ±5 ±5 ±5 ma CAPACITIVE LOAD Drive Capability Gain = +,,, pf POWER SUPPLY Rated Performance ±5 ±5 ±5 V Operating Range ±2. ±8 ±2. ±8 ±2. ±8 V Quiescent Current.5 2.4.5 2.4.5 2.4 ma T MIN T MAX.6 2.6.6 2.6.6 2.6 ma TRANSISTOR COUNT # of Transistors 8 8 8 NOTES 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 V OS / V CM between any two amplifiers, expressed in db. 4 PSRR match is the difference between V OS / V SUPPLY 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 Supply Voltage................................ ±8 V Internal Power Dissipation (+25 C)........... See Note 2 Input Voltage................................... ±V S Differential Input Voltage 3....................... ±.7 V Output Short Circuit Duration (Single Input)..... Indefinite Storage Temperature Range (Q).............................. 65 C to +5 C (N, R)........................... 65 C to +25 C Operating Temperature Range J/K........................... C to +7 C A/B......................... 4 C to +85 C T.......................... 55 C to +25 C Lead Temperature Range (Soldering seconds).... +3 C NOTES 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: 4-Pin Plastic Package: θ JA = 5 C/Watt 4-Pin Cerdip Package: θ JA = C/Watt 6-Pin SOIC Package: θ JA = C/Watt 2-Terminal LCC Package: θ JA = 5 C/Watt 3 The input pins of this amplifier are protected by back-to-back diodes. If the differential voltage exceeds ±.7 volts, external series protection resistors should be added to limit the input current to less than 25 ma. INPUT * SIGNAL * kω kω 9kΩ /4 2.5kΩ ALL 4 AMPLIFIERS ARE CONNECTED AS SHOWN PIN 4. µf µf COM. µf µf THE SIGNAL INPUT (SUCH THAT THE AMPLIFIER'S IS AT MAX AMPLITUDE WITHOUT CLIPPING OR SLEW LIMITING) IS APPLIED TO ONE AMPLIFIER AT A TIME. THE S OF THE OTHER THREE AMPLIFIERS ARE THEN MEASURED FOR CROSSTALK. PIN Figure 2a. Crosstalk Test Circuit 3
VOLTAGE Volts p-p Typical Characteristics (@ +25 C, V S = 5 V, unless otherwise noted) ORDERING GUIDE Model Temperature Range Package Option* JN C to +7 C N-4 JR C to +7 C R-6 JR-/REEL C to +7 C Tape and Reel KN C to +7 C N-4 AN 4 C to +85 C N-4 AQ 4 C to +85 C Q-4 AR 4 C to +85 C R-6 AR-REEL 4 C to +85 C Tape and Reel BQ 4 C to +85 C Q-4 SE/883B 55 C to +25 C E-2A TQ 55 C to +25 C Q-4 TQ/883B 55 C to +25 C Q-4 Chips are also available. *E = Leadless Ceramic Chip Carrier; N = Plastic DIP; Q = Cerdip; R = Small Outline (SOIC). 5 5 5 PERCENTAGE OF UNITS 4 3 2 PERCENTAGE OF UNITS 4 3 2 PERCENTAGE OF UNITS 4 3 2 8 4 +4 +8 6 8 +8 +6 2 6 +6 +2 INPUT OFFSET VOLTAGE µv INPUT BIAS CURRENT pa 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).5..5 +.5 +. +.5 5 5 2 SUPPLY VOLTAGE Volts 35 3 25 2 5 5 k k k M OFFSET VOLTAGE DRIFT µv/ C. SOURCE RESISTANCE MAY BE EITHER BALANCED OR UNBALANCED. k k k M M M SOURCE RESISTANCE Ω 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
VOLTAGE NOISE nv/ Hz 5 4 2 PERCENTAGE OF UNITS 4 3 2 CHANGE IN OFFSET VOLTAGE µv 3 2 INPUT BIAS CURRENT pa 8 6 4 2 POSITIVE I B NEGATIVE I B.8.4 +.4 +.8 INPUT OFFSET VOLTAGE DRIFT µv/ C 2 3 4 5 WARM-UP TIME Minutes 5 5 5 5 COMMON MODE VOLTAGE Volts Figure 9. Typical Distribution of Offset Voltage Drift Figure. Change in Input Offset Voltage vs. Warm-Up Time Figure. Input Bias Current vs. Common-Mode Voltage CURRENT NOISE fa/ Hz Ω 2MΩ kω V OUT Figure 2. Input Noise Voltage Spectral Density Figure 3. Input Noise Current Spectral Density Figure 4.. Hz to Hz Noise Voltage 5 +6 8 +4 6 V = ±5V S T = +25 C A QUIESCENT CURRENT µa 45 4 35 +25 C +25 C FIGURE 5 CMR db +2 + +8 +6 +4 V S = ± 5V PSR db 4 2 8 6 +PSR PSR 55 C +2 4 3 5 5 2 SUPPLY VOLTAGE ±Volts. k k k M 2. k k k M Figure 5. Quiescent Supply Current vs. Supply Voltage (per Amplifier) Figure 6. Common-Mode Rejection vs. Frequency Figure 7. Power Supply Rejection vs. Frequency 5
OPEN-LOOP VOLTAGE GAIN M M 55 C +25 C +25 C OPEN-LOOP VOLTAGE GAIN db 4 2 8 6 4 2 GAIN PHASE 3 6 9 2 5 8 PHASE SHIFT Degrees VOLTAGE SWING Volts (REFERRED TO SUPPLY VOLTAGES).5..5 +.5 +. +.5 R = kω L k 2 4 6 8 LOAD RESISTANCE kω Figure 8. Open-Loop Gain vs. Load Resistance Over Temperature 2.. k k k M M Figure 9. Open-Loop Gain and Phase vs. Frequency 5 5 2 SUPPLY VOLTAGE ±Volts Figure 2. Output Voltage Swing vs. Supply Voltage CLOSED-LOOP IMPEDANCE Ohms.. A = V A = + V I OUT = +ma. k k k V IN SQUARE WAVE INPUT /4 R F. µf. µf R 2kΩ L C L V OUT 9 % 2V 5µs Figure 2. Closed-Loop Output Impedance vs. Frequency Figure 22a. Unity Gain Follower (For Large Signal Applications, Resistor R F Limits the Current Through the Input Protection Diodes) Figure 22b. Unity Gain Follower Large Signal Pulse Response R F = kω, C L =, pf 5µs 5µs k 9 % 9 % V IN k SQUARE WAVE INPUT /4. µf. µf R L 2.5k C L V OUT 2mV 2mV Figure 22c. Unity Gain Follower Small Signal Pulse Response R F = Ω, C L = pf Figure 22d. Unity Gain Follower Small Signal Pulse Response R F = Ω, C L =, pf Figure 23a. Unity Gain Inverter Connection 6
2V 5µs 5µS 5µS 9 9 9 % % % 2mV 2mV Figure 23b. Unity Gain Inverter Large Signal Pulse Response, C L =, pf Figure 23c. Unity Gain Inverter Small Signal Pulse Response, C L = pf Figure 23d. Unity Gain Inverter Small Signal Pulse Response, C L =, pf OPTIONAL AC CMRR TRIM 2.4k R5 47.5k R4 6.34k R3 R G GAIN TRIM (5k POT) 6.34k R 49.9k R2 C Q = 4C2 ω = R6 CC2 R6 = R7 Q 2 = ω = R8 C3C4 R8 = R9 C3 4C4 DC CMRR TRIM (5k POT) V IN Ct. µf /4 /4. µf MΩ R6 MΩ R7 C2 C /4 MΩ R8 MΩ R9 C4 C3 /4 +V IN R2 2R2 INSTRUMENTATION AMPLIFIER GAIN = + + R RG (FOR R = R3, R2 = R4 + R5) ALL RESISTORS METAL FILM, % R C5 2MΩ.µF OPTIONAL BALANCE RESISTOR NETWORKS CAN BE REPLACED WITH A SHORT R C6 2MΩ.µF CAPACITORS C2 AND C4 ARE SOUTHERN ELECTRONICS MPCC, POLYCARBONATE, ±5%, 5 VOLT Figure 24. Gain of Instrumentation Amplifier with Post Filtering The instrumentation amplifier with post filtering (Figure 24) combines two applications which benefit greatly from the. 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.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 kω R = R3 = 49.9 kω.9 G Max Value of R G = 99.8 k.6 G C t 2 π (R3) 5 5 Table I. Resistance Values for Various Gains Circuit Gain R G (Max Value Bandwidth (G) R & R3 of Trim Potentiometer) ( 3 db), Hz 6.34 kω 66 kω 5k 526 Ω 6.6 kω 5k, 56.2 Ω.66 kω.5k COMMON MODE REJECTION db 6 4 2 8 6 4 2 GAIN =,.2V p-p COMMON-MODE INPUT TYPICAL MONOLITHIC IN AMP CIRCUIT TRIMMED USING CAPACITOR Ct WITHOUT CAPACITOR Ct k k Figure 25. Common-Mode Rejection vs. Frequency with and without Capacitor C t 7
The Hz, 4-pole active filter offers dc precision with a minimum of components and cost. The low current noise, I OS, and I B allow the use of MΩ resistors without sacrificing the µv/ C drift of the. This means lower capacitor values may be used, reducing cost and space. Furthermore, since the s I B is as low as its I OS, 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. OFFSET VOLTAGE OF FILTER CIRCUIT (RTI) µv Table II. Hz, 4-Pole Low-Pass Filter Recommended Component Values 8 2 6 6 2 8 WITHOUT OPTIONAL BALANCE RESISTOR, R3 WITH OPTIONAL BALANCE RESISTOR, R3 4 +4 +8 +2 TEMPERATURE o C Figure 26. V OS vs. Temperature Performance of the Hz Filter Circuit C476 24 /9 Section Section 2 Desired Low Frequency Frequency C C2 C3 C4 Pass Response (Hz) Q (Hz) Q ( F) ( F) ( F) ( F) Bessel.43.522.6.86.6.7.6.66 Butterworth..54..3.72.47.46.69. db Chebychev.648.69.948 2.8.34.98.733.385.2 db Chebychev.63.646.94 2.44.34.24.823.347.5 db Chebychev.54.75.932 2.94.46.29..29. db Chebychev.492.785.925 3.56.58.26.23.242 Specified Values are for a 3 db point of. Hz. For other frequencies simply scale capacitors C through C4 directly; i.e., for 3 Hz Bessel response, C =.387 µf, C2 =.357 µf, C3 =.533 µf, C4 =.25 µf. OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 4-Pin Cerdip (Q) Package 4-Pin Plastic DIP (N) Package 6-Pin Plastic SO (R) Package. (2.54).64 (.63) 2-Terminal LCCC (E) Package.358 (9.9).342 (8.69).4 (.2) x 45 REF 3 PLCS PRINTED IN U.S.A..5 (.27) BSC NO. PIN INDEX.28 (.7).22 (.56).2 (.5) x 45 REF 8