75 mV max Offset Voltage
1 mV/8C max Offset Voltage Drift
150 pA max Input Bias Current
0.2 pA/8C typical I
Drift
B
OUTPUT
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
OUTPUT
PRIMARY APPLICATIONS
Industrial/Process Controls
Weigh Scales
ECG/EKG Instrumentation
Low Frequency Active Filters
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 I
drift over temperature. It utilizes Super-
B
beta bipolar input transistors to achieve picoampere input bias
current levels (similar to FET input amplifiers at room temperature), while its I
(unlike a BiFET amp, for which I
typically only increases by 5× at +125°C
B
doubles every 10°C resulting
B
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.
CONNECTION DIAGRAMS
14-Pin Plastic DIP (N)
14-Pin Cerdip (Q) Packages
1
–IN
2
14
+
3
IN
+V
+
IN
–IN
AD704
S
4
(TOP VIEW)
5
6
2
7
14
OUTPUT
13
–IN
+
12
IN
–V
11
S
+
10
IN
–IN
9
3
8
OUTPUT
(E) Package
16-Pin SOIC
(R) Package
OUTPUT
1
–IN
2
14
+
IN
3
4
S
5
6
7
8
NC = NO CONNECT
AD704
(TOP VIEW)
2
3
+V
+
IN
–IN
OUTPUT
NCNC
20-Terminal LCC
16
OUTPUT
15
–IN
+
14
IN
13
–V
+
12
IN
11
–IN
10
OUTPUT
9
S
100
Since it has only 1/20 the input bias current of an AD OP07, the
AD704 does not require the commonly used “balancing”
10
B
1
TYPICAL I – nA
0.1
TYPICAL JFET AMP
AD704T
0.01
–55+25+125
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.
TEMPERATURE – °C
Figure 1. Input Bias Current Over Temperature
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 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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700Fax: 617/326-8703
AD704–SPECIFICATIONS
(@ TA = +258C, VCM = 0 V, and 615 V dc, unless otherwise noted)
ModelAD704J/AAD704K/BAD704T
ConditionsMinTypMaxMinTypMaxMinTypMaxUnits
INPUT OFFSET VOLTAGE
Initial Offset50150307530100µV
OffsetT
MIN–TMAX
1002505015080150µV
vs. Temp, Average TC0.21.50.21.01.0µV/°C
vs. Supply (PSRR)V
Lead Temperature Range (Soldering 10 seconds) . . . . +300°C
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.
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.
Ω
9k
Ω
1k
1/4
INPUT
*
SIGNAL
1k
ALL 4 AMPLIFIERS ARE CONNECTED AS SHOWN
THE SIGNAL INPUT (SUCH THAT THE AMPLIFIER'S OUTPUT IS AT MAX
*
AMPLITUDE WITHOUT CLIPPING OR SLEW LIMITING) IS APPLIED TO ONE
AMPLIFIER AT A TIME. THE OUTPUTS OF THE OTHER THREE AMPLIFIERS ARE
THEN MEASURED FOR CROSSTALK.
AD704
Ω
OUTPUT
Ω
2.5k
COM
+V
–V
S
0.1 µF
0.1 µF
S
1µF
1µF
AD704
PIN 4
AD704
PIN 11
–80
AMP4
–100
AMP2
–120
CROSSTALK – dB
–140
–160
101001k10k
FREQUENCY – Hz
AMP3
100k
Figure 2b. Crosstalk vs. Frequency
AD704
REV. A
Figure 2a. Crosstalk Test Circuit
–3–
AD704–Typical Characteristics
100
10
1.0
0.1
1k10k100k1M10M
100M
SOURCE RESISTANCE – Ω
SOURCE RESISTANCE
MAY BE EITHER BALANCED
OR UNBALANCED
OFFSET VOLTAGE DRIFT – µV/°C
ModelTemperature RangePackage Option*
AD704JN0°C to +70°CN-14
AD704JR0°C to +70°CR-16
AD704JR-/REEL0°C to +70°CTape and Reel
AD704KN0°C to +70°CN-14
AD704AN–40°C to +85°CN-14
AD704AQ–40°C to +85°CQ-14
AD704AR–40°C to +85°CR-16
AD704AR-REEL–40°C to +85°CTape and Reel
AD704BQ–40°C to +85°CQ-14
AD704SE/883B–55°C to +125°CE-20A
AD704TQ–55°C to +125°CQ-14
AD704TQ/883B–55°C to +125°CQ-14
Chips are also available.
*E = Leadless Ceramic Chip Carrier; N = Plastic DIP; Q = Cerdip;
R = Small Outline (SOIC).
(@ +258C, VS = 615 V, unless otherwise noted)
ORDERING GUIDE
50
40
30
20
PERCENTAGE OF UNITS
10
0
Figure 3. Typical Distribution of
Input Offset Voltage
+V
–0.5
–1.0
–1.5
+1.5
+1.0
+0.5
(REFERRED TO SUPPLY VOLTAGES)
–V
INPUT COMMON-MODE VOLTAGE LIMIT – Volts
Figure 6. Input Common-Mode
Voltage Range vs. Supply Voltage
–40
–80
INPUT OFFSET VOLTAGE – µV
S
S
05101520
SUPPLY VOLTAGE – Volts
0+40
+80
50
40
30
20
PERCENTAGE OF UNITS
10
0
–80
–160
INPUT BIAS CURRENT – pA
0+80
+160
Figure 4. Typical Distribution of
Input Bias Current
35
30
25
20
15
10
OUTPUT VOLTAGE – Volts p-p
5
0
1k
10k100k
FREQUENCY – Hz
1M
Figure 7. Large Signal Frequency
Response
50
40
30
20
PERCENTAGE OF UNITS
10
0
–120–600+60+120
INPUT OFFSET CURRENT – pA
Figure 5. Typical Distribution of
Input Offset Current
Figure 8. Offset Voltage Drift vs.
Source Resistance
–4–
REV. A
AD704
120
100
80
60
40
20
0
–15–10–505
10
15
COMMON MODE VOLTAGE – Volts
INPUT BIAS CURRENT – pA
NEGATIVE I
B
POSITIVE I
B
20
0.1
1
10
100
1k 10k 100k
1M
FREQUENCY – Hz
180
160
140
120
100
80
60
40
PSR – dB
+PSR
–PSR
V = ±15V
S
T = +25°C
A
FIGURE 15
50
40
30
20
PERCENTAGE OF UNITS
10
0
–0.8–0.40+0.4+0.8
INPUT OFFSET VOLTAGE DRIFT – µV/°C
Figure 9. Typical Distribution of
Offset Voltage Drift
1000
100
10
VOLTAGE NOISE – nV/ Hz
4
3
2
1
CHANGE IN OFFSET VOLTAGE – µV
0
012345
WARM-UP TIME – Minutes
Figure 10. Change in Input Off-
set Voltage vs. Warm-Up Time
1000
100
100Ω
10
CURRENT NOISE – fA/ Hz
20MΩ
10kΩ
V
OUT
Figure 11. Input Bias Current vs.
Common-Mode Voltage
1
500
450
400
350
QUIESCENT CURRENT – µA
300
REV. A
1101001000
FREQUENCY – Hz
Figure 12. Input Noise Voltage
Spectral Density
+125°C
+25°C
–55°C
0
5
SUPPLY VOLTAGE – ±Volts
1015
20
Figure 15. Quiescent Supply
Current vs. Supply Voltage (per
Amplifier)
1
110
FREQUENCY – Hz
100
Figure 13. Input Noise Current
Spectral Density
+160
+140
+120
V = ± 15V
S
+100
+80
CMR – dB
+60
+40
+20
0
0.1110 100
FREQUENCY – Hz
1k10k 100k
Figure 16. Common-Mode
Rejection vs. Frequency
–5–
1000
Figure 14. 0.1 Hz to 10 Hz Noise
Voltage
1M
Figure 17. Power Supply Rejection
vs. Frequency
AD704
05
10
1520
+0.5
+1.0
+1.5
–1.5
–1.0
–0.5
+V
S
SUPPLY VOLTAGE – ±Volts
OUTPUT VOLTAGE SWING – Volts
(REFERRED TO SUPPLY VOLTAGES)
–V
S
R = 10kΩ
L
10
0%
50µs
2V
100
90
1/4
AD704
SQUARE
WAVE INPUT
0.1 µF
0.1 µF
V
OUT
C
L
RL
2.5kΩ
–V
S
V
IN
+V
S
10kΩ
10kΩ
10M
–55 C
+25 C
1M
OPEN-LOOP VOLTAGE GAIN
100k
2
1
LOAD RESISTANCE – kΩ
468
10
+125 C
Figure 18. Open-Loop Gain vs.
Load Resistance Over Temperature
1000
100
10
1
0.1
0.01
0.001
CLOSED-LOOP OUTPUT IMPEDANCE – Ohms
110100
A = –1000
V
FREQUENCY – Hz
1k10k100k
A = +1
V
I = +1mA
OUT
Figure 21. Closed-Loop Output
Impedance vs. Frequency
140
120
100
100
80
60
40
20
OPEN-LOOP VOLTAGE GAIN – dB
0
–20
0.01 0.1 1 10 1001k10k 100k 1M 10M
FREQUENCY – Hz
PHASE
GAIN
Figure 19. Open-Loop Gain and Phase
vs. Frequency
R
F
+V
S
0.1 µF
1/4
V
IN
SQUARE
WAVE INPUT
AD704
–V
S
2kΩ
0.1 µF
Figure 22a. Unity Gain Follower
(For Large Signal Applications,
Resistor R
Limits the Current
F
Through the Input Protection
Diodes)
R
0
30
60
90
120
150
180
PHASE SHIFT – Degrees
Figure 20. Output Voltage Swing vs.
Supply Voltage
V
L
OUT
C
L
Figure 22b. Unity Gain Follower
Large Signal Pulse Response
RF = 10 kΩ, CL = 1,000 pF
100
90
10
0%
20mV
Figure 22c. Unity Gain Follower
Small Signal Pulse Response
= 0Ω, CL = 100 pF
R
F
5µs
100
90
10
0%
20mV
Figure 22d. Unity Gain Follower
Small Signal Pulse Response
= 0Ω, CL = 1,000 pF
R
F
–6–
5µs
Figure 23a. Unity Gain Inverter
Connection
REV. A
AD704
2V
100
90
10
0%
50µs
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
GAIN TRIM
(500k POT)
2R2
___
RG
49.9k
R2
1/4
AD704
–V
1MΩ
1MΩ
R6
R7
C2
0.1 µF
S
6.34k
R1
R2
__
R1
5µS
C1
__
Q =
4C2
1
1
_________
=
ω
R6 C1C2
R6 = R7
C1
1/4
AD704
R10
2MΩ
0.01µF
C5
OPTIONAL BALANCE RESISTOR
NETWORKS CAN BE REPLACED
WITH A SHORT
5µS
100
90
10
0%
20mV
Figure 23d. Unity Gain Inverter Small
Signal Pulse Response, C
C3
__
Q =
4C4
2
1
_________
=
ω
R8 C3C4
R8 = R9
1MΩ
R8
1MΩ
R9
C3
C4
1/4
AD704
R11
2MΩ
0.01µF
C6
CAPACITORS C2 AND C4 ARE
SOUTHERN ELECTRONICS MPCC,
POLYCARBONATE, ±5%, 50 VOLT
OUTPUT
= 1,000 pF
L
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:
Figure 25. Common-Mode Rejection vs. Frequency with
and without Capacitor C
t
REV. A
–7–
AD704
0.358 (9.09)
0.342 (8.69)
NO. 1 PIN
INDEX
0.040 (1.02)
x 45° REF
3 PLCS
0.020 (0.51)
x 45° REF
0.050
(1.27)
BSC
0.100 (2.54)
0.064 (1.63)
0.028 (0.71)
0.022 (0.56)
180
120
60
0
–60
–120
–180
–40
0
+40+80
+120
OFFSET VOLTAGE
OF FILTER CIRCUIT (RTI) – µV
WITHOUT OPTIONAL
BALANCE RESISTOR, R3
TEMPERATURE – C
o
WITH OPTIONAL
BALANCE RESISTOR, R3
The 1 Hz, 4-pole active filter offers dc precision with a minimum of components and cost. The low current noise, I
I
allow the use of 1 MΩ resistors without sacrificing the
B
1 µV/°C drift of the AD704. This means lower capacitor values
may be used, reducing cost and space. Furthermore, since the
AD704’s I
is as low as its IOS, over most of the MIL tempera-
B
ture 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.
Table II. 1 Hz, 4-Pole Low-Pass Filter Recommended Component Values
0.1 dB Chebychev0.6480.6190.9482.180.3040.1980.7330.0385
0.2 dB Chebychev0.6030.6460.9412.440.3410.2040.8230.0347
0.5 dB Chebychev0.5400.7050.9322.940.4160.2091.000.0290
1.0 dB Chebychev0.4920.7850.9253.560.5080.2061.230.0242
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.
OS
, and
Figure 26. VOS vs. Temperature Performance of the 1 Hz
Filter Circuit
C1476–24–10/90
14-Pin Cerdip (Q) Package
16-Pin Plastic SO (R) Package
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
14-Pin Plastic DIP (N) Package
20-Terminal LCCC (E) Package
PRINTED IN U.S.A.
–8–
REV. A
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