AD8615/AD8616/AD8618

Rev. C | Page 12 of 20

OVERLOAD RECOVERY TIME

Overload recovery time is the time it takes the output of the

amplifier to come out of saturation and recover to its linear

region. Overload recovery is particularly important in applica-

tions where small signals must be amplified in the presence of

large transients. Figure 40 and Figure 41 show the positive and

negative overload recovery times of the AD8616. In both cases,

the time elapsed before the AD8616 comes out of saturation is

less than 1 μs. In addition, the symmetry between the positive

and negative recovery times allows excellent signal rectification

without distortion to the output signal.

TIME (1

μs/DIV)

–50mV

+2.5V

0V

0V

Figure 40. Positive Overload Recovery

TIME (1

μs/DIV)

+50mV

–2.5V

0V

0V

Figure 41. Negative Overload Recovery

D/A CONVERSION

The AD8616 can be used at the output of high resolution DACs.

Their low offset voltage, fast slew rate, and fast settling time

make the parts suitable to buffer voltage output or current

output DACs.

Figure 42 shows an example of the AD8616 at the output of the

AD5542. The AD8616’s rail-to-rail output and low distortion

help maintain the accuracy needed in data acquisition systems

and automated test equipment.

AD5542

OUT

UNIPOLAR

OUTPUT

AGND

DGND

REFS

1/2

AD8616

REFF

SERIAL

INTERFACE

0.1

μF

0.1

μF

10

μF

5V

2.5V

+

CS

DIN

SCLK

LDAC

Figure 42. Buffering DAC Output

LOW NOISE APPLICATIONS

Although the AD8618 typically has less than 8 nV/√Hz of

voltage noise density at 1 kHz, it is possible to reduce it fur-

ther. A simple method is to connect the amplifiers in parallel,

as shown in Figure 43. The total noise at the output is divided

by the square root of the number of amplifiers. In this case, the

total noise is approximately 4 nV/√Hz at room temperature.

The 100 Ω resistor limits the current and provides an effective

output resistance of 50 Ω.

V–

R3

100

Ω

R1

10

Ω

V+

3

2

1

R2

1k

Ω

V–

R6

100

Ω

R4

10

Ω

V+

3

2

1

R5

1k

Ω

V–

R9

100

Ω

R7

10

Ω

V+

3

2

1

R8

1k

Ω

V–

R12

100

Ω

R10

10

Ω

V+

3

2

1

R11

1k

Ω

Figure 43. Noise Reduction