AD8432

Rev. 0 | Page 24 of 28

DIFFERENTIAL-TO-SINGLE-ENDED CONVERSION

Some applications require the low noise and high dynamic

range of the AD8432; however, they may also require a single-

ended output, rather than a differential output. The AD8129

and AD8130 differential receiver amplifier can be used for the

differential-to-single-ended conversion of the AD8432 output,

as shown in Figure 67.

The AD8129 is a low noise, high gain (10 or greater) amplifier

intended for applications over very long cables, where signal

attenuation is significant. The AD8130 is stable at a gain of 1

and can be used for applications where lower gains are required.

The AD8129 and AD8130 have user-adjustable gain, set by the

ratio of two resistors, to help compensate for losses in the

transmission line.

A transformer or balun can also be used to convert the differential

output of the AD8432 to a single-ended output. Transformers

have lower distortion; however, care must be taken to properly

match the impedance of the transformer. The test circuit for

distortion measurements in Figure 53 uses an ADTT1-1

transformer to perform differential-to-single-ended conversion.

–

–

+

+

1

8

4

5

6

7

2

BIAS

INL1

IND1

INH1

ENB

VPS1

VPS2

COMM

OPH1

OPL1

LNA1

IN1

20

Ω

499

Ω

499

Ω

20

Ω

15

Ω

0.1µF

0.1µF

0.1µF

0.1µF

0.1µF

0.1µF

GMH1

GOH1

GOL1

GML1

SERIES R IF DRIVING

HIGH CAP LOAD

AC-COUPLING CAPS

(AD8432 HAS 2.5V

OUTPUT BIAS)

AD8130

R’S PROVIDE BIAS CURRENT

PATH AND TERMINATION

IF NECESSARY

G = 12 dB

Figure 67. AD8432 Differential-to-Single-Ended Conversion Using the AD8129/AD8130 with Unity Gain