1 nV/√Hz Low Noise

Instrumentation Amplifier

AD8429

Rev. 0

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FEATURES

Low noise

1 nV/√Hz input noise

45 nV/√Hz output noise

High accuracy dc performance (AD8429BRZ)

90 dB CMRR minimum (G = 1)

50 μV maximum input offset voltage

0.02% maximum gain accuracy (G = 1)

Excellent ac specifications

80 dB CMRR to 5 kHz (G = 1)

15 MHz bandwidth (G = 1)

1.2 MHz bandwidth (G = 100)

22 V/μs slew rate

THD: −130 dBc (1 kHz, G = 1)

Versatile

±4 V to ±18 V dual supply

Gain set with a single resistor (G = 1 to 10,000)

Temperature range for specified performance

−40°C to +125°C

APPLICATIONS

Medical instrumentation

Precision data acquisition

Microphone preamplification

Vibration analysis

PIN CONNECTION DIAGRAM

TOP VIEW

(Not to Scale)

–IN

1

+IN

4

8

7

REF

6

5

AD8429

Figure 1.

GENERAL DESCRIPTION

The AD8429 is an ultralow noise, instrumentation amplifier

designed for measuring extremely small signals over a wide

temperature range (−40°C to +125°C).

The AD8429 excels at measuring tiny signals. It delivers ultralow

input noise performance of 1 nV/√Hz. The high CMRR of the

AD8429 prevents unwanted signals from corrupting the acqui-

sition. The CMRR increases as the gain increases, offering high

rejection when it is most needed. The high performance pin

configuration of the AD8429 allows it to reliably maintain high

CMRR at frequencies well beyond those of typical instrumentation

amplifiers.

The AD8429 reliably amplifies fast changing signals. Its current

feedback architecture provides high bandwidth at high gain, for

example, 1.2 MHz at G = 100. The design includes circuitry to im-

prove settling time after large input voltage transients. The AD8429

was designed for excellent distortion performance, allowing use in

demanding applications such as vibration analysis.

Gain is set from 1 to 10,000 with a single resistor. A reference

pin allows the user to offset the output voltage. This feature can

be useful to shift the output level when interfacing to a single

supply signal chain.

The AD8429 performance is specified over the extended industrial

temperature range of −40°C to +125°C. It is available in an 8-lead

plastic SOIC package.

1000

100

10

1

0.1

FREQUENCY (Hz)

1

10

100

1k

10k

100k

G = 1

G = 10

G = 100

G = 1k

Figure 2. RTI Voltage Noise Spectral Density vs. Frequency