REV. E
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AD743
Ultralow Noise
BiFET Op Amp
FEATURES
Ultralow Noise Performance
2.9 nV/
√
Hz at 10 kHz
0.38 V p-p, 0.1 Hz to 10 Hz
6.9 fA/
√
Hz Current Noise at 1 kHz
Excellent DC Performance
0.5 mV Max Offset Voltage
250 pA Max Input Bias Current
1000 V/mV Min Open-Loop Gain
AC Performance
2.8 V/s Slew Rate
4.5 MHz Unity-Gain Bandwidth
THD = 0.0003% @ 1 kHz
Available in Tape and Reel in Accordance with
EIA-481A Standard
APPLICATIONS
Sonar Preamplifiers
High Dynamic Range Filters (>140 dB)
Photodiode and IR Detector Amplifiers
Accelerometers
CONNECTION DIAGRAMS
8-Lead PDIP (N) 16-Lead SOIC (R)
AD743
8
TOP VIEW
TOP VIEW
1
2
3
7
6
8
5
4
OUT
NULL
NC
+V
S
+V
S
NC = NO CONNECT
NC = NO CONNECT
AD743
8
1
2
3
4
NC
NC
NC
OUTPUT
NC
NC
8
7
6
5
9
10
11
12
13
14
16
15
–V
S
–IN
+IN
NC
OFFSET
NULL
OFFSET
NULL
NC
NC
NC
NULL
–IN
+IN
–V
S
GENERAL DESCRIPTION
The AD743 is an ultralow noise, precision, FET input, monolithic
operational amplifier. It offers a combination of the ultralow volt-
age noise generally associated with bipolar input op amps and
the very low input current of a FET input device. Furthermore,
the AD743 does not exhibit an output phase reversal when the
negative common-mode voltage limit is exceeded.
The AD743’s guaranteed, maximum input voltage noise of
4.0 nV/√Hz at 10 kHz is unsurpassed for a FET input mono-
lithic op amp, as is the maximum 1.0 µV p-p, 0.1 Hz to 10 Hz
noise. The AD743 also has excellent dc performance with 250 pA
maximum input bias current and 0.5 mV maximum offset voltage.
The AD743 is specifically designed for use as a preamp in capaci-
tive sensors, such as ceramic hydrophones. The AD743J is rated
over the commercial temperature range of 0°C to 70°C.
The AD743 is available in a 16-lead SOIC and 8-lead PDIP.
PRODUCT HIGHLIGHTS
1. The low offset voltage and low input offset voltage drift of the
AD743 coupled with its ultralow noise performance mean
that the AD743 can be used for upgrading many applications
now using bipolar amplifiers.
2. The combination of low voltage and low current noise make
the AD743 ideal for charge sensitive applications such as
accelerometers and hydrophones.
3. The low input offset voltage and low noise level of the AD743
provide >140 dB dynamic range.
4. The typical 10 kHz noise level of 2.9 nV/√Hz permits a three
op amp instrumentation amplifier, using three AD743s, to be
built which exhibits less than 4.2 nV/√Hz noise at 10 kHz
and which has low input bias currents.
100 1k 10k 100k
1
10
100
1000
1M 10M
SOURCE RESISTANCE (⍀)
OP27 AND
RESISTOR
AD743 AND
RESISTOR
RESISTOR NOISE ONLY
AD743 AND RESISTOR
OR
OP27 AND RESISTOR
(
)
(– – –)
( — )
R
SOURCE
R
SOURCE
O
E
IN
P
U
T V
O
LTA
G
E
N
O
IS
E
(nV
/
H
z
)
Figure 1. Input Voltage Noise vs. Source Resistance
