CONNECTION DIAGRAM
AD549
OFFSET NULL
OUTPUT
NC
V
OFFSET
NULL
NONINVERTING
INPUT
6
7
1
3
4
5
2
8
V+
GUARD PIN, CONNECTED TO CASE
INVERTING
INPUT
1
4
5
V
OS
TRIM
15V
10k
NC = NO CONNECTION
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.
a
Ultralow Input Bias Current
Operational Amplifier
AD549*
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
FEATURES
Ultralow Bias Current: 60 fA max (AD549L)
250 fA max (AD549J)
Input Bias Current Guaranteed Over Common-Mode
Voltage Range
Low Offset Voltage: 0.25 mV max (AD549K)
1.00 mV max (AD549J)
Low Offset Drift: 5 V/ C max (AD549K)
20 V/ C max (AD549J)
Low Power: 700 A max Supply Current
Low Input Voltage Noise: 4 V p-p 0.1 Hz to 10 Hz
MIL-STD-883B Parts Available
APPLICATIONS
Electrometer Amplifiers
Photodiode Preamp
pH Electrode Buffer
Vacuum lon Gage Measurement
PRODUCT DESCRIPTION
The AD549 is a monolithic electrometer operational amplifier
with very low input bias current. Input offset voltage and input
offset voltage drift are laser trimmed for precision performance.
The AD549's ultralow input current is achieved with "Topgate"
JFET technology, a process development exclusive to Analog
Devices. This technology allows the fabrication of extremely low
input current JFETs compatible with a standard junction-
isolated bipolar process. The 10
15
common-mode impedance,
a result of the bootstrapped input stage, insures that the input
current is essentially independent of common-mode voltage.
The AD549 is suited for applications requiring very low input
current and low input offset voltage. It excels as a preamp for a
wide variety of current output transducers such as photodiodes,
photomultiplier tubes, or oxygen sensors. The AD549 can also
be used as a precision integrator or low droop sample and hold.
The AD549 is pin compatible with standard FET and electrom-
eter op amps, allowing designers to upgrade the performance of
present systems at little additional cost.
The AD549 is available in a TO-99 hermetic package. The case
is connected to Pin 8 so that the metal case can be independently
connected to a point at the same potential as the input termi-
nals, minimizing stray leakage to the case.
*Protected by Patent No. 4,639,683.
The AD549 is available in four performance grades. The J, K,
and L versions are rated over the commercial temperature range
0
C to +70
C. The S grade is specified over the military tem-
perature range of 55
C to +125
C and is available processed to
MIL-STD-883B, Rev C. Extended reliability PLUS screening is
also available. Plus screening includes 168-hour burn-in, as
well as other environmental and physical tests derived from
MIL-STD-883B, Rev C.
PRODUCT HIGHLIGHTS
1. The AD549's input currents are specified, 100% tested and
guaranteed after the device is warmed up. Input current is
guaranteed over the entire common-mode input voltage
range.
2. The AD549's input offset voltage and drift are laser trimmed
to 0.25 mV and 5
V/
C (AD549K), 1 mV and 20
V/
C
(AD549J).
3. A maximum quiescent supply current of 700
A minimizes
heating effects on input current and offset voltage.
4. AC specifications include 1 MHz unity gain bandwidth and
3 V/
s slew rate. Settling time for a 10 V input step is 5
s to
0.01%.
5. The AD549 is an improved replacement for the AD515,
OPA104, and 3528.
AD549SPECIFICATIONS
Model
AD549J
AD549K
AD549L
AD549S
Min
Typ
Max
Min
Typ
Max
Min
Typ
Max
Min
Typ
Max
Units
INPUT BIAS CURRENT
1
Either Input, V
CM
= 0 V
150
250
75
100
40
60
75
100
fA
Either Input, V
CM
=
10 V
150
250
75
100
40
60
75
100
fA
Either Input at T
MAX
,
V
CM
= 0 V
11
4.2
2.8
420
pA
Offset Current
50
30
20
30
fA
Offset Current at T
MAX
2.2
1.3
0.85
125
pA
INPUT OFFSET VOLTAGE
2
Initial Offset
0.5
1.0
0.15
0.25
0.3
0.5
0.3
0.5
mV
Offset at T
MAX
1.9
0.4
0.9
2.0
mV
vs. Temperature
10
20
2
5
5
10
10
15
V/
C
vs. Supply
32
100
10
32
10
32
10
32
V/V
vs. Supply, T
MIN
to T
MAX
32
100
10
32
10
32
32
50
V/V
Long-Term Offset Stability
15
15
15
15
V/Month
INPUT VOLTAGE NOISE
f = 0.1 Hz to 10 Hz
4
4
6
4
4
V p-p
f = 10 Hz
90
90
90
90
nV/
Hz
f = 100 Hz
60
60
60
60
nV/
Hz
f = 1 kHz
35
35
35
35
nV/
Hz
f = 10 kHz
35
35
35
35
nV/
Hz
INPUT CURRENT NOISE
f = 0.1 Hz to 10 Hz
0.7
0.5
0.36
0.5
fA rms
f = 1 kHz
0.22
0.16
0.11
0.16
fA/
Hz
INPUT IMPEDANCE
Differential
V
DIFF
=
1
10
13
1
10
13
1
10
13
1
10
13
1
pF
Common Mode
V
CM
=
10
10
15
0.8
10
15
0.8
10
15
0.8
10
15
0.8
pF
OPEN-LOOP GAIN
V
O
@
10 V, R
L
= 10 k
300
1000
300
1000
300
1000
300
1000
V/mV
V
O
@
10 V, R
L
= 10 k,
T
MIN
to T
MAX
300
800
300
800
300
800
300
800
V/mV
V
O
=
10 V, R
L
= 2 k
100
250
100
250
100
250
100
250
V/mV
V
O
=
10 V, R
L
= 2 k,
T
MIN
to T
MAX
80
200
80
200
80
200
25
150
V/mV
INPUT VOLTAGE RANGE
Differential
3
20
20
20
20
V
Common-Mode Voltage
10
+10
10
+10
10
+10
10
+10
V
Common-Mode Rejection Ratio
V = +10 V, 10 V
80
90
90
100
90
100
90
100
dB
T
MIN
to T
MAX
76
80
80
90
80
90
80
90
dB
OUTPUT CHARACTERISTICS
Voltage @ R
L
= 10 k,
T
MIN
to T
MAX
12
+12
12
+12
12
+12
12
+12
V
Voltage @ R
L
= 2 k,
T
MIN
to T
MAX
10
+10
10
+10
10
+10
10
+10
V
Short Circuit Current
15
20
35
15
20
35
15
20
35
15
20
35
mA
T
MIN
to T
MAX
9
9
9
6
mA
Load Capacitance Stability
G = +1
4000
4000
4000
4000
pF
FREQUENCY RESPONSE
Unity Gain, Small Signal
0.7
1.0
0.7
1.0
0.7
1.0
0.7
1.0
MHz
Full Power Response
50
50
50
50
kHz
Slew Rate
2
3
2
3
2
3
2
3
V/
s
Settling Time, 0.1%
4.5
4.5
4.5
4.5
s
0.01%
5
5
5
5
s
Overload Recovery,
50% Overdrive, G = 1
2
2
2
2
s
(@ +25 C and V
S
= +15 V dc, unless otherwise noted)
REV. A
2
Model
AD549J
AD549K
AD549L
AD549S
Min
Typ
Max
Min
Typ
Max
Min
Typ
Max
Min
Typ
Max
Units
POWER SUPPLY
Rated Performance
15
15
15
15
V
Operating
5
18
5
18
5
18
5
18
V
Quiescent Current
0.60
0.70
0.60
0.70
0.60
0.70
0.60
0.70
mA
TEMPERATURE RANGE
Operating, Rated Performance
0
+70
0
+70
0
+70
55
+125
C
Storage
65
+150
65
+150
65
+150
65
+150
C
PACKAGE OPTION
TO-99 (H-08A)
AD549JH
AD549KH
AD549LH
AD549SH, AD549SH/883B
Chips
AD549JChips
NOTES
1
Bias current specifications are guaranteed after 5 minutes of operation at T
A
= +25
C. Bias current increases by a factor of 2.3 for every 10
C rise in temperature.
2
Input offset voltage specifications are guaranteed after 5 minutes of operation at T
A
= +25
C.
3
Defined as max continuous voltage between the inputs such that neither input exceeds
10 V from ground.
Specifications subject to change without notice.
All min and max specifications are guaranteed. Specifications in boldface are tested on all production units at final electrical test. Results from those tests are used to
calculate outgoing quality levels.
METALIZATION PHOTOGRAPH
Dimensions shown in inches and (mm).
Contact factory for latest dimensions.
ABSOLUTE MAXIMUM RATINGS
1
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18 V
Internal Power Dissipation . . . . . . . . . . . . . . . . . . . . . . 500 mW
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18 V
2
Output Short Circuit Duration . . . . . . . . . . . . . . . . . Indefinite
Differential Input Voltage . . . . . . . . . . . . . . . . . . +V
S
and V
S
Storage Temperature Range (H) . . . . . . . . . . 65
C to +125
C
Operating Temperature Range
AD549J (K, L) . . . . . . . . . . . . . . . . . . . . . . . . 0
C to +70
C
AD549S . . . . . . . . . . . . . . . . . . . . . . . . . . 55
C to +125
C
Lead Temperature Range (Soldering 60 sec) . . . . . . . . +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.
2
For supply voltages less than
18 V, the absolute maximum input voltage is equal
to the supply voltage.
AD549
REV. A
3
WARNING!
ESD SENSITIVE DEVICE
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD549 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
AD549Typical Characteristics
SUPPLY VOLTAGE
V
INPUT VOLTAGE
V
20
15
10
5
0
0 5 10 15 20
+V
IN
V
IN
Figure 1. Input Voltage Range
vs. Supply Voltage
SUPPLY VOLTAGE
V
800
700
600
500
400
AMPLIFIER QUIESCENT CURRENT A
0 5 10 15 20
Figure 4. Quiescent Current
vs. Supply Voltage
TEMPERATURE
C
3000
OPEN-LOOP GAIN V/mV
55 25 5 35 65 95 125
1000
300
100
Figure 7. Open-Loop Gain vs.
Temperature
SUPPLY VOLTAGE
V
20
15
10
5
0
OUTPUT VOLTAGE SWING
V
0 5 10 15 20
+V
OUT
V
OUT
+25
C
R
L
= 10k
Figure 2. Output Voltage
Swing vs. Supply Voltage
INPUT COMMON-MODE VOLTAGE V
120
100
90
80
70
COMMON-MODE REJECTION RATIO dB
15 10 0 +10 +15
110
Figure 5. CMRR vs. Input
Common-Mode Voltage
WARM-UP TIME Minutes
30
|V
OS
| V
0 1 2 3 4 5 6 7
25
20
15
10
5
0
Figure 8. Change in Offset
Voltage vs. Warm-Up Time
LOAD RESISTANCE
30
25
20
10
0
10 100 1k 10k 100k
5
15
OUTPUT VOLTAGE SWING Volts p-p
V
S
=
15 VOLTS
Figure 3. Output Voltage
Swing vs. Load Resistance
SUPPLY VOLTAGE
V
3000
OPEN-LOOP GAIN V/mV
0 5 10 15 20
1000
300
100
Figure 6. Open-Loop Gain vs.
Supply Voltage
COMMON-MODE VOLTAGE
V
50
INPUT CURRENT fA
10 5 0 5 10
40
35
20
30
25
45
Figure 9. Input Bias Current
vs. Common-Mode Voltage
REV. A
4
AD549
REV. A
5
POWER SUPPLY VOLTAGE
V
50
INPUT CURRENT fA
0 5 10 15 20
40
35
20
30
25
45
Figure 10. Input Bias Current
vs. Supply Voltage
FREQUENCY Hz
100
80
60
40
40
OPEN LOOP GAIN dB
10 100 1k 10k 100k 1M 10M
20
0
20
100
80
60
40
40
20
0
20
PHASE MARGIN
Figure 13. Open-Loop
Frequency Response
FREQUENCY Hz
160
140
120
80
40
10 100 1k 10k
60
100
NOISE SPECTRAL DENSITY nV/
Hz
20
Figure 11. Input Voltage Noise
Spectral Density
OUTPUT VOLTAGE SWING V
FREQUENCY Hz
40
35
30
20
10
10 100 1k 10k 100k 1M
15
25
5
0
Figure 14. Large Signal
Frequency Response
SOURCE RESISTANCE
100k
INPUT NOISE VOLTAGE V p-p
100k 1M 10M 100M 1G 10G 100G
1k
100
0.1
10
1
10k
RESISTOR
JOHNSON NOISE
WHENEVER JOHNSON NOISE IS GREATER THAN
AMPLIFIER NOISE, AMPLIFIER NOISE CAN BE
CONSIDERED NEGLIGIBLE FOR THE APPLICATION
1kHz BANDWIDTH
10Hz
BANDWIDTH
AMPLIFIER GENERATED NOISE
Figure 12. Noise vs. Source
Resistance
FREQUENCY Hz
100
80
60
40
CMRR dB
10 100 1k 10k 100k 1M 10M
20
0
20
Figure 15. CMRR vs. Frequency
FREQUENCY Hz
120
100
80
60
20
PSRR dB
10 100 1k 10k 100k 1M 10M
40
20
0
+ SUPPLY
SUPPLY
Figure 16. PSRR vs. Frequency
SETTLING TIME s
10
5
0
5
10
OUTPUT VOLTAGE SWING V
0 1 2 3 4 5
5mV
10mV
1mV
1mV
5mV
10mV
Figure 17. Output Voltage
Swing and Error vs.
Settling Time
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