AD797

Data Sheet

Rev. K | Page 16 of 19

Differential Line Receiver

The differential receiver circuit of Figure 47 is useful for many

applications, from audio to MRI imaging. The circuit allows

extraction of a low level signal in the presence of common-

mode noise. As shown in Figure 48, the AD797 provides this

function with only 9 nV/√Hz noise at the output. Figure 49

shows the AD797 20-bit THD performance over the audio band

and the 16-bit accuracy to 250 kHz.

**

**

AD797

6

2

3

1kΩ

DIFFERENTIAL

INPUT

1kΩ

1kΩ

1kΩ

20pF

50pF*

20pF

–VS

+VS

4

7

8

VOUT

OPTIONAL

USE THE POWER SUPPLY BYPASSING

SHOWN IN FIGURE 35.

*

**

Figure 47. Differential Line Receiver

16

6

10M

12

8

100

10

10

14

1M

100k

10k

1k

FREQUENCY (Hz)

Figure 48. Output Voltage Noise Spectral Density

for Differential Line Receiver

FREQUENCY (Hz)

–90

300k

–120

–130

300

100

–110

–100

100k

30k

10k

3k

1k

0.003

0.0003

0.001

0.0001

WITHOUT

OPTIONAL

50pF CN

WITH

OPTIONAL

50pF CN

MEASUREMENT

LIMIT

Figure 49. Total Harmonic Distortion (THD) vs. Frequency

for Differential Line Receiver

A General-Purpose ATE/Instrumentation I/O Driver

The ultralow noise and distortion of the AD797 can be

combined with the wide bandwidth, slew rate, and load drive

of a current feedback amplifier to yield a very wide dynamic

range general-purpose driver. The circuit shown in Figure 50

combines the AD797 with the AD811 in just such an application.

Using the component values shown, this circuit is capable of

better than −90 dB THD with a ±5 V, 500 kHz output signal.

The circuit is, therefore, suitable for driving a high resolution

ADC as an output driver in automatic test equipment (ATE)

systems. Using a 100 kHz sine wave, the circuit drives a 600 Ω

load to a level of 7 V rms with less than −109 dB THD and a

10 kΩ load at less than −117 dB THD.

*

7

*

*

*

+VS

+VS

–VS

AD797

22pF

2kΩ

649Ω

649Ω

1kΩ

R2

6

3

4

2

7

AD811

6

2

4

3

–VS

*USE THE POWER SUPPLY BYPASSING SHOWN IN FIGURE 35.

VOUT

VIN

Figure 50. A General-Purpose ATE/Instrumentation I/O Driver