AD817
H IGH SP EED D AC BUFFER
(10.24 V for a 1 kΩ resistor). Note that since the DAC gener-
ates a positive current to ground, the voltage at the amplifier
output will be negative. A 100 Ω series resistor between the
noninverting amplifier input and ground minimizes the offset
effects of op amp input bias currents.
T he wide bandwidth and fast settling time of the AD817 make
it a very good output buffer for high speed current output D/A
converters like the AD668. As shown in Figure 38, the op amp
establishes a summing node at ground for the DAC output. T he
output voltage is determined by the amplifier’s feedback resistor
+15V
10µF
TO ANALOG
GROUND PLANE
0.1µF
1
MSB
VCC 24
23
22
21
REFCOM
REFIN1
REFIN2
2
3
1V NOMINAL
REFERENCE INPUT
10kΩ
4
5
1kΩ
I OUT 20
100Ω
ANALOG
OUTPUT
AD668
DIGITAL
INPUTS
6
RLOAD
19
18
17
16
AD817
ANALOG GROUND PLANE
7
ACOM
LCOM
IBPO
ANALOG
SUPPLY
GROUND
8
10µF
9
0.1µF
–15V
10
11
12
15
14
V
EE
THCOM
VTH
1kΩ
100pF
+5V
LSB
13
Figure 38. High Speed DAC Buffer
O UTLINE D IMENSIO NS
D imensions shown in inches and (mm).
8-P in P lastic Mini-D IP
(N-8)
8-P in SO IC
(SO -8)
8
5
0.25
(6.35)
8
1
5
4
0.31
(7.87)
PIN 1
0.1574 (4.00)
0.1497 (3.80)
PIN 1
1
4
0.2440 (6.20)
0.2284 (5.80)
0.30 (7.62)
REF
0.39 (9.91) MAX
0.1968 (5.00)
0.1890 (4.80)
0.035±0.01
(0.89±0.25)
0.0196 (0.50)
0.0099 (0.25)
x 45
°
0.165±0.01
(4.19±0.25)
0.0688 (1.75)
0.0532 (1.35)
0.0098 (0.25)
0.0040 (0.10)
0.011±0.003
(0.28±0.08)
0.18±0.03
(4.57±0.76)
8
0
°
°
0.125
(3.18)
MIN
0.0500 (1.27)
0.0160 (0.41)
0.0500
(1.27)
BSC
0.0192 (0.49)
0.0138 (0.35)
0.0098 (0.25)
0.0075 (0.19)
15
°
0°
0.10
(2.54)
0.018±0.003
(0.46±0.08)
0.033
(0.84)
NOM
SEATING
PLANE
BSC
–12–
REV. B
ADI [ ADI ]
