AD8615/AD8616/AD8618
5V
2.5V
OVERLOAD RECOVERY TIME
10
μF
+
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.
0.1μF
0.1μF
SERIAL
INTERFACE
V
REFF
REFS
DD
1/2
AD8616
CS
UNIPOLAR
OUTPUT
DIN
AD5542
OUT
SCLK
LDAC
DGND
AGND
Figure 42. Buffering DAC Output
LOW NOISE APPLICATIONS
V
R
A
= ±2.5V
= 10kΩ
= 100
S
L
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
+2.5V
V
= 50mV
IN
0V
0V
3
V
IN
R3
–50mV
V+
V–
1
1
1
1
R1
2
100Ω
10Ω
TIME (1μs/DIV)
R2
Figure 40. Positive Overload Recovery
1kΩ
V
= ±2.5V
S
3
R
= 10kΩ
= 100
= 50mV
L
V
R6
V+
V–
A
V
R4
2
IN
100Ω
10Ω
–2.5V
0V
0V
R5
V
OUT
1kΩ
3
2
R9
V+
V–
R7
100Ω
10Ω
R8
+50mV
1kΩ
3
2
TIME (1μs/DIV)
R12
V+
V–
R10
100Ω
Figure 41. Negative Overload Recovery
10Ω
D/A CONVERSION
R11
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.
1kΩ
Figure 43. Noise Reduction
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.
Rev. C | Page 12 of 20
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