AD8615/AD8616/AD8618
5V
2.5V
OVERLOAD RECOVERY TIME
10µF
+
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 applications 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
V
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 further. 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
V+
V–
1
–50mV
R1
2
100Ω
10Ω
TIME (1µs/DIV)
R2
Figure 40. Positive Overload Recovery
1kΩ
3
2
R6
V+
V–
1
1
1
V
R
A
= ±2.5V
= 10kΩ
= 100
= 50mV
S
R4
L
100Ω
V
10Ω
V
IN
R5
–
2.5V
V
OUT
0V
0V
1kΩ
3
2
R9
V+
V–
R7
100Ω
10Ω
R8
1kΩ
+50mV
3
2
R12
V+
V–
R10
TIME (1µs/DIV)
100Ω
10Ω
Figure 41. Negative Overload Recovery
R11
D/A CONVERSION
1kΩ
The AD8616 can be used at the output of high resolution DACs.
The low offset voltage, fast slew rate, and fast settling time make
the part suitable to buffer voltage output or current output
DACs.
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. E | Page 12 of 20
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