REV. E

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AD743

Ultralow Noise

BiFET Op Amp

FEATURES

Ultralow Noise Performance

2.9 nV/

0.38

V p-p, 0.1 Hz to 10 Hz

6.9 fA/

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

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

–IN

+IN

NC

OFFSET

NULL

OFFSET

NULL

NC

NC

NC

NULL

–IN

+IN

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

(

)

(– – –)

( — )

O

E

Figure 1. Input Voltage Noise vs. Source Resistance