Picoampere Input Current
Bipolar Op Amp
a
AD705
FEATURES
DC PERFORMANCE
CONNECTION DIAGRAM
25 V max Offset Voltage (AD705T)
0.6 V/؇C max Drift (AD705K/T)
100 pA max Input Bias Current (AD705K)
600 pA max IB Over MIL Temperature Range (AD705T)
114 dB min CMRR (AD705K/T)
114 dB min PSRR (AD705T)
200 V/mV min Open Loop Gain
0.5 V p-p typ Noise, 0.1 Hz to 10 Hz
600 A max Supply Current
Plastic Mini-DIP (N)
Cerdip (Q) and
Plastic SOIC (R) Packages
OFFSET
NULL
OFFSET
NULL
TOP VIEW
1
2
3
4
8
7
6
5
–IN
+IN
V–
V+
OUTPUT
OVER
COMP
AD705
AC PERFORMANCE
0.15 V/µs Slew Rate
800 kHz Unity Gain Crossover Frequency
10,000 pF Capacitive Load Drive Capability
Low Cost
Available in 8-Pin Plastic Mini-DlP, Hermetic Cerdip
and Surface Mount (SOIC) Packages
MIL-STD-883B Processing Available
Dual Version Available: AD706
Quad Version: AD704
levels, the commonly used “balancing” resistor (connected be-
tween the noninverting input of a bipolar op amp and ground) is
not required.
The AD705 is an excellent choice for use in low frequency ac-
tive filters in 12- and 14-bit data acquisition systems, in preci-
sion instrumentation and as a high quality integrator.
APPLICATIONS
The AD705 is internally compensated for unity gain and is
available in five performance grades. The AD705J and AD705K
are rated over the commercial temperature range of 0°C to
+70°C. The AD705A and AD705B are rated over the industrial
temperature range of –40°C to +85°C. The AD705T is rated
over the military temperature range of –55°C to +125°C and is
available processed to MIL-STD-883B, Rev. C.
Low Frequency Active Filters
Precision Instrumentation
Precision Integrators
PRODUCT DESCRIPTION
The AD705 is a low power bipolar op amp that has the low in-
put bias current of a BiFET amplifier but which offers a signifi-
cantly lower IB drift over temperature. The AD705 offers many
of the advantages of BiFET and bipolar op amps without their
inherent disadvantages. It utilizes superbeta bipolar input tran-
sistors to achieve the picoampere input bias current levels of
FET input amplifiers (at room temperature), while its IB typi-
cally only increases 5 times vs. BiFET amplifiers which exhibit a
1000X increase over temperature. This means that, at room
temperature, while a typical BiFET may have less IB than the
AD705, the BiFET’s input current will increase to a level of
several nA at +125°C. Superbeta bipolar technology also per-
mits the AD705 to achieve the microvolt offset voltage and low
noise characteristics of a precision bipolar input amplifier.
The AD705 is offered in three varieties of 8-pin package: plastic
DIP, hermetic cerdip and surface mount (SOIC). “J” grade
chips are also available.
PRODUCT HIGHLIGHTS
1. The AD705 is a low drift op amp that offers BiFET level
input bias currents, yet has the low IB drift of a bipolar ampli-
fier. It upgrades the performance of circuits using op amps
such as the LT1012.
2. The combination of Analog Devices’ advanced superbeta
processing technology and factory trimming provides both
low drift and high dc precision.
3. The AD705 can be used in applications where a chopper am-
plifier would normally be required but without the chopper’s
inherent noise and other problems.
The AD705 is a high quality replacement for the industry-
standard OP07 amplifier while drawing only one sixth of its
power supply current. Since it has only 1/20th the input bias
current of an OP07, the AD705 can be used with much higher
source impedances, while providing the same level of dc preci-
sion. In addition, since the input bias currents are at picoAmp
REV. B
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.
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Tel: 617/329-4700
Fax: 617/326-8703