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AD549 d
Datasheet
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Analog Devices AD549 d Datasheet

Ultralow Input Bias Current

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 µV/°C max (AD549K) 20 µV/°C max (AD549J)
Low power
700 µA max supply current
Low input voltage noise
4 µV p-p 0.1 Hz to 10 Hz
MIL-STD-883B parts available

APPLICATIONS

Electrometer amplifiers Photodiode preamp pH electrode buffer Vacuum ion gauge measurement

PRODUCT DESCRIPTION

The AD5491 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 part’s ultralow input current is achieved with Topgate JFET technology, a process development exclusive to Analog Devices, Inc. This technology allows fabrication of extremely low input current JFETs compatible with a standard junction isolated bipolar process. The 10 results from the bootstrapped input stage, ensures that the input current is essentially independent of common-mode voltage.
The AD549 is suited for applications that require 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 electrometer op amps, allowing designers to upgrade the performance of present systems at little additional cost.
15
Ω common-mode impedance, which
Operational Amplifier
AD549

CONNECTION DIAGRAM

GUARD PIN, CONNECTED TO CASE
NC
OFFSET NULL
INVERTING
INPUT
NONINVERTING
INPUT
NC = NO CONNECTION
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 terminals, minimizing stray leakage to the case.
The AD549 is available in four performance grades. The J, K, and L versions are rated over the commercial temperature range of 0°C to +70°C. The S grade is specified over the military temperature 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 µV/°C (AD549K), and 1 mV and 20 µV/°C (AD549J).
3. A maximum quiescent supply current of 700 µA minimizes
heating effects on input current and offset voltage.
4. AC specifications include 1 MHz unity gain bandwidth
and 3 V/µs slew rate. Settling time for a 10 V input step is 5 µs to 0.01%.
1
2
3
1
8
AD549
4
V–
10kΩ
VOS TRIM
Figure 1.
V+
7
5
OFFSET NULL
5
4
6
OUTPUT
–15V
00511-001
Rev. D
1
Protected by Patent No. 4,639,683.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
www.analog.com
AD549
TABLE OF CONTENTS
Specifications..................................................................................... 3
Common-Mode Input Voltage Overload................................ 12
Absolute Maximum Ratings............................................................ 5
ESD Caution.................................................................................. 5
Typical Performance Characteristics ............................................. 6
Functional Description ..................................................................10
Minimizing Input Current ........................................................ 10
Circuit Board Notes ................................................................... 10
Offset Nulling.............................................................................. 11
AC Response with High Value Source and Feedback Resistance
.................................................................................... 12
REVISION HISTORY
5/04—Data Sheet Changed from Rev. C to Rev. D
Updated Format..............................................................Universal
Changes to Features...................................................................... 1
Updated Outline Dimensions................................................... 18
Added Ordering Guide.............................................................. 18
Differential Input Voltage Overload ........................................ 13
Input Protection ......................................................................... 13
Sample and Difference Circuit to Measure Electrometer Leakage Currents
Photodiode Interface ................................................................. 14
Temperature Compensated pH Probe Amplifier................... 17
Outline Dimensions....................................................................... 18
Ordering Guide .......................................................................... 18
........................................................................ 13
10/02—Data Sheet Changed from Rev. B to Rev. C.
Deleted PRODUCT HIGHLIGHTS #5..........................................1
Edits to SPECIFICATIONS..............................................................3
Deleted METALLIZATION PHOTOGRAPH ..............................3
Updated OUTLINE DIMENSIONS .............................................13
7/02—Data Sheet Changed from Rev. A to Rev. B.
Edits to SPECIFICATIONS..............................................................2
Rev. D | Page 2 of 20
AD549

SPECIFICATIONS

@ 25°C and VS = ±15 V dc, unless otherwise noted. 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.
Table 1.
AD549J AD549K AD549L AD549S Parameter Min Typ Max Min Typ Max Min Typ Max Min Typ Max Unit
INPUT BIAS CURRENT1
Either Input, VCM = 0 V 150 Either Input, VCM = ±10 V 150 250 75 100 40 60 75 100 fA Either Input at T
, VCM = 0 V 11 4.2 2.8 420 pA
MAX
Offset Current 50 30 20 30 fA Offset Current at T
2.2 1.3 0.85 125 pA
MAX
INPUT OFFSET VOLTAGE2
Initial Offset 0.5 Offset at T
MAX
vs. Temperature 10 vs. Supply 32 vs. Supply, T
MIN
to T
32
MAX
Long-Term Offset Stability 15 15 15 15 µV/month
INPUT VOLTAGE NOISE
f = 0.1 Hz to 10 Hz 4 4 f = 10 Hz 90 90 90 90
f = 100 Hz 60 60 60 60 f = 1 kHz 35 35 35 35 f = 10 kHz 35 35 35 35
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
INPUT IMPEDANCE
Differential
V
= ±1 1013||1 1013||1 1013||1 1013||1 Ω||pF
DIFF
Common Mode
VCM = ±10 1015||0.8 1015||0.8 1015||0.8 1015||0.8 Ω||pF
OPEN-LOOP GAIN
VO @ ±10 V, RL = 10 kΩ
1000
300
VO @ ±10 V, RL = 10 kΩ,
T
to T
MAX
MIN
VO = ±10 V, RL = 2 kΩ
300 800 300 800 300 800 300 800 V/mV
250
100
VO = ±10 V, RL = 2 kΩ,
T
to T
MIN
MAX
80 200 80 200 80 200 25 150 V/mV
INPUT VOLTAGE RANGE
Differential3 ±20 ±20 ±20 ±20 V Common-Mode Voltage
−10
Common-Mode Rejection Ratio
V = +10 V, −10 V T
to T
MAX
MIN
90
80
80
76
OUTPUT CHARACTERISTICS
Voltage @ RL = 10 kΩ,
T
to T
MAX
MIN
Voltage @ RL = 2 kΩ, T Short-Circuit Current T
to T
MIN
9 9 9 6 mA
MAX
MIN
to T
−12 +12 −12 +12 −12 +12 −12 +12 V
MAX
−10 15
20
Load Capacitance Stability
G = +1 4000 4000 4000 4000 pF
75
250
0.15
1.0
1.9
2
20
10
100
10
100
300
100
+10 −10
90 80
+10 −10 35 15
100
0.25
0.4 5 32 32
6
1000
250
+10 −10
100 90
20
+10 −10 35 15
40
0.3
5 10 10
60
0.5
0.9 10 32 32
75
0.3
10 10 32
100
0.5
2.0 15 32 50
fA
mV mV µV/°C µV/V µV/V
4 4 µV p-p
nV/√
Hz
nV/√
Hz
nV/√
Hz
nV/√
Hz
fA/√
Hz
1000
300
250
100
100
90
90
80
20
+10 −10
+10 −10 35 15
1000 V/mV
300
250 V/mV
100
100 dB
90
90 dB
80
20
+10
+10 35
V
V mA
Rev. D | Page 3 of 20
AD549
AD549J AD549K AD549L AD549S Parameter Min Typ Max Min Typ Max Min Typ Max Min Typ Max Unit
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/µs Settling Time, 0.1% 4.5 4.5 4.5 4.5 µs Settling Time, 0.01% 5 5 5 5 µs Overload Recovery, 50%
Overdrive, G = −1
POWER SUPPLY
Rated Performance ±15 ±15 ±15 ±15 V Operating Quiescent Current 0.60
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) Chips AD549JH AD549KH AD549LH AD549SH/883B
1
Bias current specifications are guaranteed after five minutes of operation at TA = 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 five minutes of operation at TA = 25°C.
3
Defined as max continuous voltage between the inputs, such that neither input exceeds ±10 V from ground.
2 2 2 2 µs
±5
±18 ±5
0.70
0.60
±18 ±5
0.60
0.70
±18 ±5
0.70
0.60
±18
0.70
V mA
Rev. D | Page 4 of 20
AD549

ABSOLUTE MAXIMUM RATINGS

Table 2.
Parameter Rating
Supply Voltage ±18 V Internal Power Dissipation 500 mW Input Voltage Output Short Circuit Duration Indefinite Differential Input Voltage +VS and −VS 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
1
±18 V
1
For supply voltages less than ±18 V, the absolute maximum input voltage is
equal to the supply voltage

ESD 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 this product 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.
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; 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.
Rev. D | Page 5 of 20
AD549

TYPICAL PERFORMANCE CHARACTERISTICS

20
800
15
+V
IN
10
–V
INPUT VOLTAGE (V)
5
0
0 5 10 15 20
SUPPLY VOLTAGE (V)
IN
Figure 2. Input Voltage Range vs. Supply Voltage
20
25°C
= 10kΩ
R
L
15
10
5
OTUPUT VOLTAGE SWING (V)
0
0 5 10 15 20
SUPPLY VOLTAGE (V)
Figure 3. Output Voltage Swing vs. Supply Voltage
30
700
600
500
AMPLIFIER QUIESCENT CURRENT (µA)
00511-002
400
0 5 10 15 20
SUPPLY VOLTAGE (±V)
00511-005
Figure 5. Quiescent Current vs. Supply Voltage
120
+V
OUT
–V
OUT
00511-003
110
100
90
80
COMMON-MODE REJECTION RATIO (dB)
70
–20 –10 0 10 20
INPUT COMMON-MODE VOLTAGE (V)
00511-006
Figure 6. CMRR vs. Input Common-Mode Voltage
3000
25
20
15
10
5
OTUPUT VOLTAGE SWING (V p-p)
0
10 100 1k 10k 100k
LOAD RESISTANCE (Ω)
VS =±15V
Figure 4. Output Voltage Swing vs. Load Resistance
00511-004
Rev. D | Page 6 of 20
1000
300
OPEN-LOOP GAIN (V/mV)
100
0 5 10 15 20
SUPPLY VOLTAGE (V)
Figure 7. Open-Loop Gain vs. Supply Voltage
00511-007
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