Datasheet

AD8615/AD8616/AD8618
Rev. E | 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 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.
TIME (1µs/DIV)
V
S
= ±2.5V
R
L
= 10kΩ
A
V
= 100
V
IN
= 50mV
–50mV
+2.5V
0
V
0
V
0
4648-040
Figure 40. Positive Overload Recovery
TIME (1µs/DIV)
V
S
=±2.5V
R
L
= 10kΩ
A
V
= 100
V
IN
= 50mV
+50mV
– 2.5V
0V
0V
04648-041
Figure 41. Negative Overload Recovery
D/A CONVERSION
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 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
V
OUT
UNIPOLAR
OUTPUT
AGNDDGND
REFS
1/2
AD8616
REFFV
DD
SERIAL
INTERFACE
0.1
µF
0.1µF
10µF
5
V
2.5
V
+
CS
DIN
SCLK
LDAC
0
4648-042
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 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–
R3
100Ω
R1
10Ω
V+
V
IN
3
2
1
R2
1kΩ
V–
R6
100Ω
R4
10Ω
V+
3
2
1
R5
1kΩ
V–
R9
100Ω
R7
10Ω
V+
3
2
1
R8
1kΩ
V–
R12
100Ω
R10
10Ω
V+
3
2
1
R11
1kΩ
V
OUT
04648-043
Figure 43. Noise Reduction