AD830

REV. A

–12–

SUPPLIES, BYPASSING AND GROUNDING (FIGURE 29)

The AD830 is capable of operating over a wide range of supply

voltages, both single and dual supplies. The coupling may be dc

or ac provided the input and output voltages stay within the

specified common-mode voltage limits. For dual supplies, the

device works from

±4 V to ±16.5 V. Single supply operation is

possible over +8 V to +33 V. It is also possible to operate the

part with split supply voltages (e.g., +24 V, –5 V) for special

applications such as level shifting. The primary constraint is that

the total potential between the two supplies does not exceed

33 V.

Inclusion of power supply bypassing capacitors is necessary to

achieve stable behavior and the specified performance. It is es-

pecially important when driving low resistance loads. At a mini-

mum, connect a 0.1

µF ceramic capacitor at the supply lead of

the AD830 package. In addition, for the best by passing, we rec-

ommend connecting a 0.01

µF ceramic capacitor and 4.7 µF

tantalum capacitor to the supply lead going to the AD830.

0.1

µF

LOAD

GND

LEAD

AND

0.01

µF

4.7

µF

AND

LOAD

GND

LEAD

(a)

(b)

Figure 29. Supply Decoupling Options

The AD830 is designed by its functionality to be capable of

rejecting noise and dissimilar potentials in the ground lines.

Therefore, proper care is necessary to realize the benefits of the

differential amplification of the part. Separation of the input and

output grounds is crucial in rejection of the common mode

noise at the inputs and eliminating any ground drops on the in-

put signal line. For example, connecting the ground of a coaxial

cable to the AD830 output common (board ground) could de-

grade the CMR and also introduce power-down loading on

cable grounds. However, it is also necessary as in any electronic

system, to provide a return path for bias currents back to their

original power supply. This is accomplished by providing a con-

nection between the differing grounds through a modest imped-

Ω).

Single Supply Operation

The AD830 is capable of operating in single power supply appli-

cations down to a voltage of +8 V, with the generalized connec-

tion shown in Figure 30. There is a constraint on the

common-mode voltage at the input and output which estab-

lishes the range for these voltages. Direct coupling may be used

for input and output voltages which lie in these ranges. Any gain

network applied needs to be referred to the output common

connection or have an appropriate offset voltage. In situations

where the signal lies at a common voltage outside the common

mode range of the AD830 direct coupling will not work, so ac

coupling should be used. A tested application included later in

this data sheet (Figure 42), shows how to easily accomplish cou-

pling to the AD830. For single supply operation where direct

coupling is desired the input and output common-mode curves

(Figures 31 and 32) should be used.

5

8

4

1

2

3

7

6

A=1

AD830

G

M

C

+

–

V

P

+

–

+

–

V

OUT

V

OCM

V

ICM

V

IN

V

G

M

Figure 30. General Single Supply Connection

30

0

2.0

4

0

12

16

24

1.6

1.2

0.8

0.4

DIFFERENTIAL INPUT VOLTAGE – V

PEAK

8

28

20

V

V

V

TO GND

Figure 31. Input Common-Mode Range for Single Supply

0

30

4

10

12

16

24

26

22

18

14

SUPPLY VOLTAGE – Volts

8

28

20

TO V

P

TO GND

Figure 32. Output Swing Limit for Single Supply