Ultralow Distortion,

Ultralow Noise Op Amp

AD797

Rev. F

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FEATURES

Low noise

0.9 nV/√Hz typical (1.2 nV/√Hz maximum) input voltage

noise at 1 kHz

50 nV p-p input voltage noise, 0.1 Hz to 10 Hz

Low distortion

−120 dB total harmonic distortion at 20 kHz

Excellent ac characteristics

800 ns settling time to 16 bits (10 V step)

110 MHz gain bandwidth (G = 1000)

8 MHz bandwidth (G = 10)

280 kHz full power bandwidth at 20 V p-p

20 V/μs slew rate

Excellent dc precision

80 μV maximum input offset voltage

Specified for ±5 V and ±15 V power supplies

High output drive current of 50 mA

APPLICATIONS

Professional audio preamplifiers

IR, CCD, and sonar imaging systems

Spectrum analyzers

Ultrasound preamplifiers

Seismic detectors

Σ-Δ ADC/DAC buffers

PIN CONFIGURATION

AD797

TOP VIEW

DECOMPENSATION

AND DISTORTION

NEUTRALIZATION

OUTPUT

OFFSET NULL

8

7

6

5

Figure 1. 8-Lead Plastic Dual In-Line Package [PDIP] and

8-Lead Standard Small Outline Package [SOIC]

GENERAL DESCRIPTION

The AD797 is a very low noise, low distortion operational

amplifier ideal for use as a preamplifier. The low noise of

0.9 nV/√Hz and low total harmonic distortion of −120 dB at

audio bandwidths give the AD797 the wide dynamic range

necessary for preamps in microphones and mixing consoles.

Furthermore, the AD797’s excellent slew rate of 20 V/μs and

110 MHz gain bandwidth make it highly suitable for low

frequency ultrasound applications.

The AD797 is also useful in infrared (IR) and sonar imaging

applications, where the widest dynamic range is necessary. The

low distortion and 16-bit settling time of the AD797 make it

ideal for buffering the inputs to Σ-Δ ADCs or the outputs of

high resolution DACs, especially when the device is used in

critical applications such as seismic detection or in spectrum

analyzers. Key features such as a 50 mA output current drive

and the specified power supply voltage range of ±5 V to ±15 V

make the AD797 an excellent general-purpose amplifier.

5

0

10M

3

1

100

2

10

4

1M

100k

10k

1k

FREQUENCY (Hz)

Figure 2. AD797 Voltage Noise Spectral Density

–90

–130

300k

–120

300

100

–110

–100

100k

30k

10k

3k

1k

FREQUENCY (Hz)

0.001

0.0003

0.0001

MEASUREMENT

LIMIT

Figure 3. THD vs. Frequency