Analog Devices AD546 Datasheet
1 pA Monolithic Electrometer
a
FEATURES
DC PERFORMANCE
1 mV max Input Offset Voltage
Low Offset Drift: 20 mV/8C
1 pA max Input Bias Current
Input Bias Current Guaranteed Over Full
Common-Mode Voltage Range
AC PERFORMANCE
3 V/ms Slew Rate
1 MHz Unity Gain Bandwidth
Low Input Voltage Noise: 4 mV p-p, 0.1 Hz to 10 Hz
Available in a Low Cost, 8-Pin Plastic Mini-DIP
Standard Op Amp Pinout
APPLICATIONS
Electrometer Amplifiers
Photodiode Preamps
pH Electrode Buffers
Log Ratio Amplifiers
Operational Amplifier
AD546*
CONNECTION DIAGRAM
8-Pin Plastic
Mini-DIP Package
PRODUCT DESCRIPTION
The AD546 is a monolithic electrometer combining the virtues
of low (1 pA) input bias current with the cost effectiveness of a
plastic mini-DIP package. Both input offset voltage and input
offset voltage drift are laser trimmed, providing very high performance for such a low cost amplifier.
Input bias currents are reduced significantly by using “topgate”
JFET technology. The 10
resulting from a bootstrapped input stage, insures that input
bias current is essentially independent of common-mode voltage
variations.
The AD546 is suitable for applications requiring both minimal
levels of input bias current and low input offset voltage. Applications for the AD546 include use as a buffer amplifier for current output transducers such as photodiodes and pH probes. It
may also be used as a precision integrator or as a low droop rate
sample and hold amplifier. The AD546 is pin compatible with
standard op amps; its plastic mini-DIP package is ideal for use
with automatic insertion equipment.
The AD546 is available in two performance grades, all rated
over the 0°C to +70°C commercial temperature range, and
packaged in an 8-pin plastic mini-DIP.
*Covered by Patent No. 4,639,683.
15
Ω common-mode impedance,
PRODUCT HIGHLIGHTS
1. The input bias current of the AD546 is specified, 100%
tested and guaranteed with the device in the fully warmed-up
condition.
2. The input offset voltage of the AD546 is laser trimmed to
less than 1 mV (AD546K).
3. The AD546 is packaged in a standard, low cost, 8-pin
mini-DIP.
4. A low quiescent supply current of 700 µA minimizes any
thermal effects which might degrade input bias current and
input offset voltage specifications.
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
AD546–SPECIFICATIONS
(@ +258C and 615 V dc, unless otherwise noted)
AD546J AD546K
Model Conditions Min Typ Max Min Typ Max Units
INPUT BIAS CURRENT
1
Either Input VCM = 0 V 0.2 1 0.2 0.5 pA
Either Input V
= ±10 V 0.1 1 0.2 0.5 pA
CM
Either Input
@ T
MAX
Either Input V
Offset Current V
VCM = 0 V 40 20 pA
= ±10 V 40 20 pA
CM
= 0 V 0.17 0.09 pA
CM
Offset Current
@ T
MAX
VCM = 0 V 13 7 pA
INPUT OFFSET
Initial Offset 21pA
Offset @ T
MAX
32mV
vs. Temperature 20 20 µV/°C
vs. Supply 100 100 µV/V
vs. Supply T
MIN–TMAX
100 100 µV/V
Long-Term Stability 20 20 µV/Month
INPUT VOLTAGE NOISE f = 0.1 Hz to 10 Hz 4 4 µV p-p
f = 10 Hz 90 90 nV/√
f = 100 Hz 60 60 nV/√
Hz
Hz
f = 1 kHz 35 35 nV/√Hz
f = 10 kHz 35 35 nV/√Hz
INPUT CURRENT NOISE f = 0.1 Hz to 10 Hz 1.3 1.3 fA rms
f = 1 kHz 0.4 0.4 fA/√Hz
INPUT IMPEDANCE
Differential V
Common Mode V
OPEN LOOP GAIN V
T
MIN–TMAX
T
MIN–TMAX
INPUT VOLTAGE RANGE
Differential
3
= ±1 V 10
DIFF
= ±10 V 10
CM
= ±10 V
O
R
= 10 kΩ 300 1000 300 1000 V/mV
LOAD
V
= ±10 V
O
R
= 10 kΩ 300 800 300 800 V/mV
LOAD
V
= ±10 V
O
R
= 2 kΩ 100 250 100 250 V/mV
LOAD
V
= ±10 V
O
R
= 2 kΩ 80 200 80 200 V/mV
LOAD
13
i110
15
i0.8 10
13
i1 ΩipF
15
i0.8 ΩipF
±20 ± 20 V
Common-Mode Voltage –10 +10 –10 +10 V
Common-Mode Rejection Ratio V
= ±10 V 80 90 84 100 dB
CM
T
MIN
to T
MAX
76 80 76 80 dB
OUTPUT CHARACTERISTICS
Voltage R
= 10 kΩ –12 +12 –12 +12 V
LOAD
R
= 2 kΩ –10 +10 –10 +10 V
LOAD
Current Short Circuit 15 20 35 15 20 35 mA
Load Capacitance Stability Gain = +1 4000 4000 pF
–2–
REV. A
AD546
WARNING!
ESD SENSITIVE DEVICE
AD546J AD546K
Model Conditions Min Typ Max Min Typ Max Units
FREQUENCY RESPONSE
Gain BW, Small Signal G = –1 0.7 1.0 0.7 1.0 MHz
Full Power Response V
Slew Rate, Unity Gain G = –1 2 3 2 3 V/µs
Settling Time to 0.1% 4.5 4.5 µs
Overload Recovery 50% Overdrive
POWER SUPPLY
Rated Performance ±15 ± 15 V
Operating Range 65 618 65 618 V
Quiescent Current 0.60 0.7 0.60 0.7 mA
Transistor Count # of Transistors 50 50
PACKAGE OPTIONS
Plastic Mini-DIP (N-8) AD546JN AD546KN
NOTES
1
Bias current specifications are guaranteed maximum, at either input, after 5 minutes of operation at T
every 10°C rise in temperature.
2
Input offset voltage specifications are guaranteed after 5 minutes of operation at TA = +25°C.
3
Defined as max continuous voltage between inputs, such that neither exceeds ± 10 V from ground.
Specifications subject to change without notice.
Specifications in boldface are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels. All min and
max specifications are guaranteed, although only those shown in boldface are tested on all production units.
= 20 V p-p 50 50 kHz
O
to 0.01% 5 5 µs
Gain = –1 2 2 µs
= +25°C. Bias current increases by a factor of 2.3 for
A
ABSOLUTE MAXIMUM RATINGS
1
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±18 V
Internal Power Dissipation . . . . . . . . . . . . . . . . . . . . . .500 mW
Input Voltage
2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±18 V
Output Short Circuit Duration . . . . . . . . . . . . . . . . . Indefinite
Differential Input Voltage . . . . . . . . . . . . . . . . . . +V
and –V
S
S
Storage Temperature Range . . . . . . . . . . . . . –65°C to +125°C
Operating Temperature Range . . . . . . . . . . . . . . 0°C to +70°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.
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 AD546 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.
REV. A
–3–
AD546–Typical Characteristics
RL = 10kΩ
SUPPLY VOLTAGE ± V
OPEN LOOP GAIN – V/mV
3000
1000
100
05 20
10 15
300
(VS = 615 V, unless otherwise noted)
20
15
+V
IN
10
–V
5
INPUT VOLTAGE RANGE ± V
0
05 20
SUPPLY VOLTAGE ± V
IN
10 15
Figure 1. Input Voltage Range
vs. Supply Voltage
800
700
600
20
+25oC
= 10kΩ
R
L
15
10
5
OUTPUT VOLTAGE RANGE ± V
0
05 20
SUPPLY VOLTAGE ± V
+V
OUT
–V
OUT
10 15
Figure 2. Output Voltage Range
vs. Supply Voltage
120
110
100
90
30
25
20
15
10
5
OUTPUT VOLTAGE SWING – Volts p-p
0
100
LOAD RESISTANCE – Ω
VS = ± 15 VOLTS
Figure 3. Output Voltage Swing
vs. Resistive Load
100k10k1k10
500
QUIESCENT CURRENT – µA
400
05 20
10 15
SUPPLY VOLTAGE ± V
Figure 4. Quiescent Current vs.
Supply Voltage
3000
1000
300
OPEN LOOP GAIN – V/mV
RL = 10kΩ
100
–25 125
–55
5356595
TEMPERATURE – oC
Figure 7. Open Loop Gain vs.
Temperature
80
COMMON MODE REJECTION RATIO – dB
70
–15
INPUT COMMON MODE VOLTAGE – V
Figure 5. CMRR vs. Input
Common-Mode Voltage
30
25
20
15
∆ |VOS| –µV
10
5
0
01 7
23456
WARM-UP TIME – Minutes
Figure 8. Change in Offset
Voltage vs. Warm-Up Time
+15–10 0 +10
Figure 6. Open Loop Gain vs.
Supply Voltage
300
250
200
150
INPUT BIAS CURRENT – fA
100
–10 –5 10
COMMON-MODE VOLTAGE – Volts
05
+25oC
Figure 9. Input Bias Current vs.
Common-Mode Voltage
–4–
REV. A
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