AD797

REV. C

–13–

Differential Line Receiver

The differential receiver circuit of Figure 43 is useful for many

applications from audio to MRI imaging. It allows extraction of

a low level signal in the presence of common-mode noise. As

shown in Figure 44, the AD797 provides this function with only

9 nV/

√Hz noise at the output. Figure 45 shows the AD797’s

20-bit THD performance over the audio band and 16-bit accu-

racy to 250 kHz.

20pF

USE POWER SUPPLY

BYPASSING SHOWN IN

FIGURE 32.

**

AD797

1k

Ω

**

**

1k

Ω

2

3

6

7

4

8

1k

Ω

DIFFERENTIAL

INPUT

20pF

OUTPUT

50pF*

*OPTIONAL

1k

Ω

Figure 43. Differential Line Receiver

16

6

10M

12

8

100

10

10

14

1M

100k

10k

1k

FREQUENCY — Hz

Figure 44. Output Voltage Noise Spectral Density for

Differential Line Receiver

A General Purpose ATE/Instrumentation Input/Output

Driver

The ultralow noise and distortion of the AD797 may be com-

bined 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 of Figure 46 combines the

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

–90

–130

300k

–120

300

100

–110

–100

100k

30k

10k

3k

1k

0.003

0.0003

0.001

FREQUENCY – Hz

WITH

OPTIONAL

MEASUREMENT

LIMIT

WITHOUT

OPTIONAL

0.0001

Figure 45. Total Harmonic Distortion (THD) vs. Frequency

for Differential Line Receiver

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 high resolution A/D converters and

as an output driver in automatic test equipment (ATE) systems.

Using a 100 kHz sine wave, the circuit will drive a 600

Ω load to

a level of 7 V rms with less than –109 dB THD, and a 10 k

Ω

load at less than –117 dB THD.

1k

Ω

USE POWER SUPPLY

BYPASSING SHOWN IN

FIGURE 32.

**

INPUT

22pF

OUTPUT

2k

Ω

649

Ω

649

Ω

R2

AD797

**

2

7

3

4

6

**

AD811

**

2

7

3

4

6

**

2

Figure 46. A General Purpose ATE/lnstrumentation Input/

Output Driver